What is the Citrus Gall Wasp?
Around Melbourne, Citrus Gall Wasp (Bruchophagus fellis) has become a large problem for backyard citrus growers. It is a small, 3 mm in length, shiny, black wasp that is native to Australia. It originated in northern parts of Australia where the native finger lime is the normal host plant. However, the Citrus Gall Wasp has also adapted to use our introduced citrus trees as host plants.
It was first recorded as a pest of citrus in Queensland and New South Wales in the 1930s. During the last decade, it has spread to the Riverina and Sunraysia regions of New South Wales, Victoria, South Australia and the southern parts of Western Australia.
The Citrus Gall Wasp causes unsightly lumps in citrus trees. This is the tree’s reaction to foreign bodies of the wasp larvae, that are incubating in the branch. Traditional thinking is that these galls are stressful to the trees. It is also believed to cause weaker branches and lower the productivity of the trees.
There are two natural predators of the citrus gall wasp. The wasps Megastigmus brevivalvus and M. trisulcus insert their eggs directly into the citrus gall wasp egg. There it slowly develops in the host larva, eventually killing it. When well established, these wasps can parasitise more than 90% of gall wasp larvae. Neither of these natural predators has established populations in Melbourne, to make a significant impact on the gall wasp.
Citrus Gall Wasp life cycle
The Citrus Gall Wasp has a life cycle that spans one calendar year. The adult wasp emerges from its woody gall in late spring or early summer. The emergence of the wasp is determined by the temperature. Most wasps emerge around the same time (within 20 days of each other). Warmer springs will see them emerge earlier than cooler springs.
Once the wasp has emerged, it has only 5 to 7 days to mate and then lay up to 100 eggs under the green bark of a citrus tree.
The eggs hatch after 2 to 3 weeks and feed within the stem for the next 9 to 10 months. During this time the tree will promote woody growth around the infected area. These galls become visible from about December and will gradually enlarge through autumn and winter.
After a short pupation period in spring, the adults emerge from little holes in the galls and the cycle continues.
Adult wasps normally do not move very far, but can be transported longer distances on prevailing winds or by movement of infested branches or trees. They usually re-infect the same tree, or another one nearby.
The NSW DPI has been trialling some different treatments in commercial citrus orchards. One organic treatment method is showing promise. It involves spraying calcined kaolin clay (Surround®) twice during the citrus gall wasp emergence period. This disrupts the egg laying and has shown to reduce gall occurrence significantly.
Observations that I’ve made when growing citrus
Citrus trees are a popular fruit tree and many of my clients have them in their gardens. Over the years, this has given me plenty of opportunities to watch and observe the Citrus Gall Wasp in action. Here are a few of my observations:
- Citrus Gall Wasps tend to infect mainly lemons, grapefruit and to a lesser extent oranges.
- Whilst they will infect mandarin and Tahitian lime trees, they seem to prefer lemons and grapefruit as their host
- I’ve never seen an infected cumquat
- I’ve never noticed them on any of the native limes such as the finger lime or sunrise lime. This is ironic, because they are the original host plants for the citrus gall wasp. I’ve had a lower number of native citrus trees available to inspect for gall wasp, so this may not be accurate. UPDATE 07/07/16… this how now been disproved. Our gardening community report that the gall wasp does very much infect the native citrus and cause galls (see comments section below).
- The gall wasp always lays its eggs in very lush, new growth. This is evident as galls are most easily seen six months later at the base of light-green coloured shoots.
- Citrus trees are traditionally fertilised heavily in spring, summer and autumn. Heavy fertilising in spring promotes a flush of new growth that is preferred by Citrus Gall Wasp.
- There is a public awareness campaign to “Prune in June”. Removing all citrus galls from a tree in June results in a flush of strong new growth in spring. This new growth is preferred by Citrus Gall Wasp.
- Slow growing, underfed trees are rarely infected by Citrus Gall Wasp in spring
- The Citrus Gall Wasp problem is now so widespread and established in Melbourne that eradication of the wasp from the area is going to be impossible through pruning or other mechanical methods.
- Citrus trees infested with citrus galls can still be quite productive. I’m not sure that the galls are as stressful to the tree as traditional theories have made out.
An alternative theory on controlling Citrus Gall Wasp in Melbourne
Based on the observations above, I have come up with some theoretical practices that are worth trialling for growing citrus in Melbourne.
Avoid pruning out the gall wasps in winter. Doing so unbalances the tree so that it has a larger root system area than foliage area. This causes the tree to try to restore the balance by growing vigorously in spring. The vigorous spring growth results in a flush of new foliage that the gall wasp prefers. Yearly pruning regimes, such as this perpetuates the cycle. The “Prune in June” program is likely to result in a downward spiral of the tree over the course of several years until you are left with nothing but a stick. Most fruit trees are covered in fruit (and possibly blossom) in winter, so it is another good reason not to “Prune in June”.
Avoid heavily fertilising trees in winter or spring. This also results in a flush of new growth that the gall wasp prefers and perpetuates the cycle. Unfortunately, citrus trees are heavy feeders and require a lot of nitrogen rich nutrients. Without these heavy feeds, the leaves will go yellow and they may not be as productive as heavily fed trees (although, even well fed citrus trees may turn yellow in winter). In some cases, I’ve waited until December to feed my citrus trees and this has meant that they have remained uninfected by the gall wasps.
Feeding citrus trees in February or March can result in a second flush of new growth that is preferred by the Citrus Leaf Miner. This means that to avoid pests the only time to feed citrus in Melbourne is late December and all of January. This is probably not enough for supporting productive healthy citrus trees.
There is a conundrum for the Melbourne based citrus grower. It seems we can have a well-fed productive tree, or an underfed, yellowing, pest-free tree, but not both!
Grow a variety that is not preferred by the Citrus Gall Wasp. Most people know someone else with a lemon tree and in winter they are a staple of local food swaps. So why not grow a mandarin, native finger lime or cumquat instead? There are plenty of other varieties out there to try. Check out my citrus variety guide for more ideas.
The Leaf, Root & Fruit Citrus Gall Wasp Experiment
To test these theories, I set up a trial to see which management practice is most beneficial for growing citrus.
I purchased ten small lemon trees that are relatively identical in size, shape and stage of growth. The trees were paired up and allocated to five different treatments:
- Citrus Galls pruned out in June every year, fertilised monthly Sep to May.
- Citrus Galls pruned out in June every year, fertilised monthly in Dec and Jan only.
- Citrus Galls not pruned out, fertilised monthly Sep to May.
- Citrus Galls not pruned out, fertilised monthly in Dec and Jan only
- Citrus Galls not pruned out, fertilised monthly Sep to May, treated with calcined kaolin clay (Surround®).
This experiment ran for several years with some interesting outcomes. check out my Citrus Gall Wasp Experiment page for more information.
Want to know more about growing citrus in Melbourne? Check out my handy five part guide to growing citrus.
Have you made any similar observations to mine?
Do you have any thoughts or great ideas on how to control citrus gall wasp in Melbourne?
Please include them in the comments section below.
I have a native finger lime and it developed lots of galls last season 🙁
Well there you go… I was wondering if the infected native limes just didn’t react by producing a gall, but I’m glad to now know that they do, and that it means my trees are gall free. Thanks for clearing that up Joelle!
Hi , for many years i have had a Meyer lemon tree in my back yard that is loaded with lemons but the last couple of years I noticed these bulb things on some of the branches , tried cutting some out after hearing about the gall wasp and putting one of those long tube things in the tree that traps insects by the sticky substance on the outside , but noticed the bulb things are still there and the tree is still loaded and the lemons that are ripe seem to have got smaller and have some Brown patches on them , don’t know the what is needed to make the tree healthy again and the lemons become larger again like they were before…..
Hi Gary, it sounds like there are quite a few issues going on with your tree. Without seeing the tree in person it is difficult to diagnose fully.
Once present, the galls never disappear, but the wasps inside them probably will.
I would guess that the lemons are small because there are lots on the tree and the tree didn’t get enough water over the summer to support them properly. We had a very dry summer and many trees have suffered because of this.
The brown patches on the lemons are probably scale. They wont damage the inside of the fruit and they should still be fine to use. Scale is usually a sign that the tree is stressed. Often a lack of nutrients, air flow or water.
Hope that helps you understand what’s going on a bit more. As I said, it is difficult to diagnose without seeing the tree.
Good Luck & Happy Gardening!
Duncan
1. In my garden in Brunswick the wasps have got into lemon, lime and lemonade trees. I also think they may have been in a native lime that wasn’t growing at all until I moved it and cut off a suspect looking area.
2. Kevin the Brunswick plumber says that you should put the prunings in a bucket of water or cut the gall with a blade, to kill the wasps before sending to landfill in a bag.
3. There are trees around here that have been neglected which are covered in huge amounts of gall and really have become unhealthy and unproductive (except from the wasps’ point of view).
4. Generally I just cut them off every couple of months and this works to keep under control.
Hi Nancy,
“Kevin the Brunswick Plumber” is right on the money in terms of soaking the prunings to kill the larvae.
Thanks for sharing your observations and tips with us.
Duncan
How long should you soak the branches?
A few days should do the trick Jody!
Good Luck and Happy Gardening!
Duncan
I live in Melbourn’s south east on 1/3 acre with a lush garden.
I have been diligent removing the galls. I told my neighbour I was sure another neighbour had an infestation, then she confessed her tree is badly infested.
I kept watching my lemon trees and I noticed nothing (after having removed every gall).
After a run of a few really sunny days before xmas , here and there on new growth , what looked like some ants. A close look I realized they were gall wasps.
They must have come from my neighbours.
They were just here on there on new growth and no where else i must stress.
I killed them and kept checking for more.
I had been watching since September 1 and thought they would be on the move much sooner frim what I have read.
The hot weather was definitely a call to arms for the wasps.
Since then (xmas) I have noticed some more galls, so I have cut them off or opened them up. I spray with some metho.
I tried vinigar then read it will kill my trees, i nearly did, but survived that.
I have noticed bark that you scrape off , the wood hardens and all the little holes from the wasps are like dry tunnels after a while. If you cut open the other side of the branch, there a more there live and well. The exposure one one side doesnt solve the problem.
Over time I have tried all sorts of things.
I used some coconut oil with some other goodies added to it, to smear on new growth to deter the wasps.
I also tried spraying them with a spray with smelly stuff like clove oil to confuse them
I also tried coconut oil to put on galls so the wasps got bogged .
Will the galls eventually kill trees or can they survive. I feel like my trees are never going to get any bigger because I keep removing galls.
I also used a huge spray of confidor and threw out all the lemons for a couple of years.
Thing is, because my neighbours tree is infested, i am fighting a losing battle.
I have become OCD over gall wasps.
Are there any scientists working on this problem.
I noticed opening galls exposing the wasps only works on the side of the branch or twig exposed. You virtually have to shave all round, so kill the branch saving it.
I wonder if some big lumps of plasticine wrapped round galls before the wasps hatch would muck their movements up..
There has to be a simple solution undiscovered..
When I saw the little wasps on my trees, i had removed every gall I could find, so the wasps has found there way to my yard from somewhere else and been attracted to that new growth. We have a big yard with a lot of plants.
I think they can fly better than the experts think and can smell well.
If scientists could breed some that cant fly or smell to mate with the others, it might stop them in their tracks.
For the wind to carry them to land in the perfect spot is a bit far fetched.
What if a lemon flavoured spray was made to spray on other plants so that they were attracted to plants that might kill them and not feed them..
Just another idea. I am going to try that next spring/summer
Hi Maryann,
you’ve provided some amazing suggestions and insights there. Thank you for sharing your experiences with us.
As mentioned in the article, the NSW DPI are working on the issue for larger orchards. For backyard gardeners it is probably going to be up to us to solve the problem.
Please keep us updated on your experiments. Hopefully we can all work together to come up with a simple and manageable solution.
Good Luck and Happy Gardening!
Duncan
I know the feeling well and sympathise.
Hi,
I have an old lemon tree ( 30+ years) I think it may have a problem with the wasps you mentioned in your article.
The tree has become quite woody in the centre, with new growth pointing upward no fruit as yet, in past years HAS produced lots of fruit.
Can I cut the woody parts away or will that cause more.problems?
Hi Karen,
It is very difficult for me to give accurate advice without seeing the tree. Generally speaking citrus trees can handle being cut buck severely. However, as per the article, heavy pruning of a tree results in a flush of new growth. If that flush of new growth is present when the wasps are emerging, then it is likely to result in an even heavier infestation. It also depends on if the gall wasp larvae are still present in the galls, or if they have emerged.
Good Luck & Happy Gardening!
Thank you for the information. I have never had the gall wasp until I moved to Mooroolbark – now I know why.
I bought a small lime tree 12 months ago don’t know what it was but in that short time it developed gall wasp. so disappointed as it was only very small. Can let you know if you would like.
Looking forward to hearing the results of your experiments and doing some of my own.
Hi Barbara,
Thanks for sharing your experience. Gall Wasps can be a frustrating issue . Please report back on progress, we’d really appreciate it.
Good Luck and Happy Gardening
Duncan
What about two prunings – one in Winter to remove the galls, the other in Spring to remove the lush new growth?
Hi Heather, sounds like an interesting idea and it may work. I’d think that you’d still end up removing a lot more of the plant than you might using some of the other methods. I’ve also noticed that the galls seem to form at the base of new growth. So you would probably need to prune back all of the spring growth, plus some of the older wood at the same time. Thanks for sharing your idea. If you give it a go, please let us all know how you get on.
Good Luck and Happy Gardening!
It’s good to read your thoughts and experience on the best way to manage the citrus gall wasps. We have been cutting the galls out on a more leisurely schedule, where we would notice one while walking past the tree, cutting a few out at the time. It seems to have worked for us for a few years now and the tree, which is probably 60 years old has a full yield of lemons. This year I thought I should follow the ‘Prune in June’ advice more religiously but my more ‘lazy gardener’ ways have won out, so I’m glad to have read your article as I will go back to our old ways!
I’m a big advocate for “Do Nothing Gardening”, and this is just an extension of this. Sounds like you’ve got the right take on things.
Good Luck and Happy Gardening!
I look forward to seeing the results of your trial.An excellent idea!
A couple of comments: a neighbour’s lemon tree, uncared for, unfertilised, and with minimal soft new spring growth, was covered in galls – whole branches were thick masses of gall. Very few fruit. It struck me that the huge number and density of galls was probably quite disruptive to the structure of the tree. We pruned it heavily last year; haven’t checked recently to see how it is growing. I will be interested to see.
Observing other well-fed and cared for trees, fruit production hasn’t suffered despite heavy loads of galls.
Re different citrus varieties, my observations are similar to yours: lemons, limes and grapefruit are particularly prone to gall wasp infestation. Also Japanese seedless mandarins, Makrut limes and oranges. Cumquats, Imperial and Murcott mandarins have never been never affected here.
Penny Woodward suggested on the 3CR radio garden program that spraying with eco oil or similar affects the ability of the wasps to successfully implant their eggs on the trees. I plan to try this.
I have never had the citrus leaf miner until the past season – all the trees have had some of their new growth affected, pruned trees and unpruned trees! Don’t know where they came from…
I like your lateral thinking!
Interesting observation about well fed vs weak trees Olwyn. The kaolin clay is supposed to fulfill a similar role to the eco oil. I’m pretty excited about this experiment and looking forward to sharing the results with you all.
Thanks for sharing your experience with us!
Duncan
I had a similar experience pruning a friend’s neglected lemon tree – all parts of the tree were severely infested, and the older wood had gall upon gall upon gall so that it was thick, warped, lumpy, (remember the face of the elephant man?). Some of these lumped up branches had feeble new growth coming out of it, but many also had dead sticks coming out – either new growth that had died off or older branches that had been choked by galls closer to the trunk. Many of the lumpy areas were black and rotting. I must have cut 90% off the tree, despite trying to save any less infected branches so the tree would still have some canopy. It was a brutal pruning.
The traditional method of pruning might not be right for every situation, but it would have saved this tree from years of damage.
Maybe Slice the Gall open in June, this would be much better than letting them develop. The larvae dry up an die I think with this method.
Yes, this is another method of dealing with the galls. Recently someone recommended a potato peeler as a great (and safe) tool for doing this. Thanks for sharing your tip Chris!
Hi, I’ve tried cutting through fresh galls with a knife and it seems to help in that it stops them developing into large hard ones. The larvae obviously die. The potato peeler sounds like a stroke of genius. Will give it a shot.
Cheers
Thanks for the feedback RoseMarie.
Please keep us updated on your progress
Duncan
Counter Observation…
Noted above you made the following comment, “Whilst they will infect mandarin and Tahitian lime trees, they seem to prefer lemons and grapefruit as their host”.
I have 3 citrus, Tahitian Lime, Meyer Lemon & Lisbon Lemon in close proximity and all are equally infected. I will trial the following method over the next season and advise.
* Jun-July citrus galls not pruned out, but tree lightly pruned to shape & improve airflow,
* Dec-Feb proposed time to fertilise,
* Jan-Feb galls that appear cut one side of gall to expose larvae
Cheers
Thanks for sharing your experiences with us Christopher. Your trials sounds great and we look forward to hearing the outcomes. Please keep us all updated.
Good Luck and Happy Gardening!
Look forward to your results. I moved here 4 years ago and have been pruning gall wasp from established lemon as traditionally recommended. Problem seems to have progressively worsened. Also have an established lime which wasn’t infected, until this year.
Thanks for sharing your observations Gabriella.
Good Luck and Happy Gardening!
I have a very big well established lemon tree which is highly productive. The tree had the gall wasp lumps on it when we moved into the property 10 years ago. If I tried to prune it all out, i’d only have a tiny tree left over as there as so many. Therefore, I just leave it. The leaves hide the branches well and you cannot see the lumps unless you really go up close and look. The lemons on the tree are still bountiful and so many I can’t even give them away. They’re also very large lemons, and I never even fertilise it. So I don’t think its affected the productivity or quality of the tree much at all. Therefore, i’m going to continue to just leave it and see how it all goes.
Hi Ruthie,
Thanks for sharing your experience with us. Glad to hear that your lemon tree is thriving despite the gall wasp.
Good Luck and Happy Gardening!
Duncan
Leaving a tree with gall wasps without pruning them out means your neighbours become infected. I would suggest this is not a very responsible way to go!
While your tree might be fine at the moment, it is likely to stop being a productive tree.
I have had to almost remove all of my brother’s tree a couple of months ago from a property he purchased as it was 99% covered by gall wasps. The only branches I left behind were the ones were gall wasps had emerged in previous seasons as there was no branch without some degree of infection. The tree on the new property was so stunted by the gall wasp infestation they would not find new growth and swarm out and infect the neighbourhood citrus trees.
I have a Lime tree out the front of my house and it gets swamped very year by gall wasp infections leaving it with all but one branch that isn’t affected. I suspect one of the neighbours across the road does not do anything about this infestation causing my tree to still be the same size when I bought it 6 years ago. I am at a stage where I am offering my service to prune any citrus tree with infestation just to reduce the swarming that occurs on my tree out the front (and to a lesser degree to my trees at the back).
I have found that while they like Lemon trees, they strongly prefer Tahitian Lime trees (which are my favourite) and they rarely go on orange trees.
I am using a rubberized paint for one lime tree to see if this stops them from hatching and I am going to use Surround to see how it slows down the infection.
My lemon tree has been in full production all year round for 30 years, until two years ago, when it was infested by the gall wasp.
The galls on some parts of the tree were over a foot long, the crown of the tree was leafless, and the fruit was down to 3 lemons.
So, I gave it a radical prune and took it back to bare branches during the last week of October this year with the prunings being immediately burnt.
There is no new growth at this stage, but fingers crossed for the next few months.
Thanks for sharing your experience Barry. Please keep us all updated on your outcomes.
Good Luck and Happy Gardening!
Duncan
My heavly pruned lemon tree is sprouting new leaves from the trunk and remaining thick branches. Plenty of growth; however, now the new leaves have the catepillar Papilio anactus or Dingy Swallowtail Butterfly all over it. So it’s a battle between the wasps and the caterpillars now.
I have started spraying with a commercial ready made white oil and the wasps get stuck in the oily film ( hopefully before they get a chance to lay any eggs). I no longer cut the galls out. Last year I covered the galls with petroleum jelly and the emerging wasps got stuck in the jelly. However the tree tissue surrounding the galls looked a bit ‘skanky’.
Thanks for sharing your experience with us Hel.
Good Luck and Happy Gardening!
Petroleum based oils are not the best as they are a poison (they are cheap to make). We don’t any in the food chain. Eco-Oil is an organic product made from non GMO plants seems a much better choice. Just noticed this following statement on the Eco-Oil website.
The HIPPO Enhanced eco-oil formulation replicates this defence mechanism by including these organic compounds into spray. The research clearly showed that the HIPPO Enhanced eco-oil will attract beneficial insects into the garden. Pretty amazing hey?
Hi Chris,
Have you tried this Eco-Oil product yourself in the garden? If so, what kind of results did you get?
Thanks for sharing
Duncan
Not yet tried it but have purchased it, Just waiting to the weather clears and will be trying it out down at our Macleod Organic Community Garden. We have a Citrus orchard with around 12 trees of all different Citrus. Will monitor the results as the trees are very young at this stage.
I lightly prune citrus gall wasp year round when it is found which is not an easy task standing atop a trestle ladder..
I prune back the minimum to remove the growths but they conyinue to develop.
At 80 years I am constinently advised forget it. The lemons will still produce beyond my demise.
Thanks for sharing your wisdom Dave. Glad to hear that at 80 years young you are still very much active in the garden.
Good Luck and Happy Gardening!
Duncan
I am in a rental, been here about 6 years. When we moved in there was a lemon tree that was literally 2 sticks pulling out of the ground with half a dozen leaves between them. I have never done anything to care for it (not even water) but it is now about 10-12 feet tall. I noticed for the first time this summer it was infested with gall wasp. Since noticing the plant has grown maybe another foot or 2, and has about 120 immature fruit growing. I wonder why it has only been this last year the wasps have attacked, as there has been rapid growth now for years
Hi Nicole,
In the past, perhaps the rapid growth has only occurred after the gall wasp peak emergence each summer?
Thanks for sharing your experience.
Duncan
We have 2 mandarin, 1 lime and 1 orange tree. All have Gall Wasps problem. Lime is so infected, cutting was not practical. 4 years ago, one of our mandarin tree had died of this disease.
I have read on internet not to cut infected branches, but scrape off the galls.
Our lime tree was healthy and first fruit of 5/6 in number was good size. It was flowering all year around. Then after few months, the tree started looking sick. Fruit started dropping. Less and less flowers. I thought must be soil underneath the tree making it sick. Then I read on the internet about a different solution. So, I went around the tree, which is about shoulder height and started scraping infected areas with a knife. After few days, tree looked better and started flowering again. Now, I go around the tree every week to check new galls and scrape them off. I have to see if this experiment works.
Hi Sardar,
Thanks for sharing your experience with us all. I’m glad you’ve found a solution that seems to be working.
Good Luck and Happy Gardening.
I normally prune galls as soon as they appear but I have a situation where this is not desirable. We have a young espalier orange tree in its second year and it has a gall on a branch which, from an aesthetic perspective, is irreplaceable.
Thinking about getting the guts out of a pest strip and fixing it to the gall before wrapping in aluminium foil. I will also be using sticky traps but they are a bit expensive to be plastering all over the place. Do you have any knowledge of success with home made yellow sticky traps?
Anyway, I’ll let you know how my toxic foil bandage arrangement works out.
Thanks for sharing your experience David. I look forward to hearing the outcome. Another method you could try is to use a potato peeler to remove the bark around some of the gall. This causes it to dry out and kill the wasp larvae.
I don’t advocate for using the sticky traps as they are indiscriminate and kill “good bugs” as well as the undesirable ones. The exception to this may be the ones baited with pheromones.
Good Luck and Happy Gardening!
Duncan
Thanks Duncan. I am surprised that we don’t have a paint on insecticide to kill the larvae either in the branch or as they chew their way out. Seems a no brainer with so many potential customers. I’m thinking now about mixing neat Confidor with acrylic house paint and applying to the gall. I know it’s bad for bees but they won’t be chewing their way out of my orange tree. On a related note, I ate our first ever home grown orange today and it was marvelous! The four other fruit (quite small tree) will be ripe soon and then it’ll get the treatment.
R’s David.
Neem oil?
I don’t live in Melbourne but here in Adelaide have similar issues with gall wasp (infesting kaffir lime, orange and lemon trees. A tahitian lime is less involved). I like the idea of using a peeler to ‘open’ up the galls & plan to try this – I have been cutting them out as I notice them but at this stage I will have no kaffir lime tree left if I remove them all. Ironically it seems to be the most productive branches that are most involved.
Would it be possible to water a treatment into the soil to be taken up by the roots & kill the larvae in situ?
Hi Anna,
Thanks for sharing your experience. I’m not aware of any chemical treatments that you can water into the soil to kill the gall wasp. Personally I’d be a bit worried about that same poison getting into my fruit and me ingesting it!
Great “out of the box” thinking though.
Good Luck with gall wasps. Please keep us updated on your progress.
Duncan
Informative site
Thank you
Thanks for the great feedback Iris. Glad you’ve found our site useful.
Good Luck and Happy Gardening!
Duncan
Great information- thanks for that. I have never heard of “Prune in June” and thought it was just vital to prune the galls out before the weather starts warming up ie end of July, early August. I have a dwarf lemon in a pot that has big galls on it (thanks to living in Brunswick) and plan to try the potato peeler method as I’ll end up with almost no tree if I prune!!
Thanks for the great feedback Deb.
Good Luck with the potato peeler!
Duncan
We have about a dozen citrus including grapefruit, limes, lemons, oranges and mandarins. All to a greater or lesser degree are gall wasp infested, despite vigilant gall removal throughout the year and sticky paper traps on all trees in early spring last year. The younger trees are particularly affected. Iwas wondering whether the wasp larvae might have an adverse reaction to, say, a carb soda solution directly injected into the gall? Assuming that their preferred food source of citrus sap is acidic? Anyone think this is worth a try, don’t imGine it would damage the tree itself.
Hi Roz,
It may indeed work to kill the galls in your tree. I’m not sure and can’t comment on what ipact it may have on the tree. However, I wonder how effective that will be at preventing re-infection anyway? I’d focus more on reducing the amount of tender new growth on your trees at peak gall wasp emergence.
Good Luck and Happy Gardening!
Duncan
My thought, which you could add to your experiment is prevention via the roots with something that smells bad to the wasp. Eg mosquitoes are said to not like the smell of vitamin B.
A different approach….. Just one large growing gall fairly early in 2017 was wrapped in aluminum foil and secured with insulation tape.,….no wasps emerged late that year beneath the foil, amlost like they need sunshine to hatch. The gall is still there now unwrapped (6/2018) so will or won’t they emerge this year? The basis of another experiment?
Very interesting observations Graeme. Perhaps the foil got quite hot and cooked the larvae in the gall? Please keep us updated on progress!
Good Luck and Happy Gardening!
Duncan
I have read a method on the web (sorry, I don’t remember the site but it would be organic gardening site) which suggested binding the gall with tape so the hatching wasps can’t get out, and die. I guess the tape would need to be a breathing sort. And would be removed after the hatching period. Have you heard or tried anything like this?
Hi Helen,
That sounds like it could work. However, it also seems a lot of work. I’d prefer to focus on reducing the susceptibility of the tree to infestation – prevention is better than cure!
If you were going to give it a go then grafting tape might be the solution. Please let me know the outcome if you try it.
Good Luck and Happy Gardening!
Duncan
Thank you Duncan. I will try grafting tape. The galls are on several branches of a small pot-planted tree so it wont be difficult to bind them. I will try grafting tape and I will monitor what happens. And let you know.
I tried grafting tape, but couldn’t make it stick together. Please give guidance on how to use kaolin if you are a backyard gardener, eg can one use a spray bottle? Dilution?
Just come across this site, I have an idea I’m going to try ,using cling film as a wrap around. I’ll cut the roll into 25- 50mm strips and use these to bind the galls. 2 or 3 turns should be enough. Could be a cheap solution if it works as there is 30m per roll and you could get up to 10 roll from each packet.
Hi Allan,
Thanks for sharing your observations. Many folks are recommending similar actions. However, on a big tree it is time consuming and only treats the symptoms. I’d rather focus on prevention in the first place.
Stay Safe & Keep Gardening!
Duncan
Excellent article – evidence is indeed the main thing currently missing from the debate. The only thing that appears to be omitted from this article is mention of the disease Citrus Gall Wasp mania, which affects a proportion of people who own citrus trees. I have this affliction (and one of the commenters below appears to share it). I can’t leave a gall wasp on the tree and am constantly checking my trees for gall wasp throughout the year. My wife has given up protesting at my obsession. I will be keen to follow the experiments. Cheers Jon
Hi Jon,
Thanks for providing my team and I with a great laugh. CGWM does appear to be quite the affliction in some citrus growers. One of my main gardening mantras is “Relax” and I wish those who share your disease would do the same! We garden for fun, not to get ourselves in a tizz over something as minuscule as a gall wasp.
good Luck and Happy Gardening
Duncan
Yesterday 7 August 2018 I found lots of gall wasps have infected my Myer lemon tree. I have pruned all affected branches and bagvin seal plastic bag. 2/3 of my mid size lemon tree now is 2/3 bald. I went to Bunnings I got two unit gall wasp catches(yellow tube) and hanging underneath the tree.
Would appreciate to advise do I need to apply any chemical or fertiliser on those cutter branches. If yes can you recommend.
Hope my tree will survive and be able blossom again.
Thanks
Thanks for your comments Kenny. It’s too early to put the gall wasp traps out – they don’t emerge until November/December. Putting them out at this stage will be catching beneficial insects but no gall wasps.
It’s also the wrong time of the yer to be fertilizing the trees. I’d wait until the weather warms up a bit more. I hope that your tree doesn’t respond and grow too quickly. If so, it will just get re-infested with gall wasps again later in the year.
Good Luck and Happy Gardening.
Duncan
My lemon tree has been affected by the Citrus Gall Wasp. I am located in Bendigo. I have been told by a nursery to get rid of the plant as it will keep reinfecting itself. My question is am I able to keep the soil that it has been planted in? Or will that be affected by the gall wasp too?
Hi Ann-Maree,
Firstly, it sounds like your plant nursery is trying to drum up new business by encouraging people to remove infested trees. As the article points out, the wasps are here to stay and we need to find ways to reduce their likelihood of infecting our trees rather than just removing them.
If you were to remove the tree then the soil will not be infected by the gall wasp. That being said the quality of your soil is very important, especially for citrus trees that have high fertilizer requirements. Perhaps take a look at our potting mix blog post for more information.
Good Luck and Happy Gardening!
Duncan
I have reard that mint leaves boiled with a mixture of cider vinegar mixtwd is an effect spray.is this true .
Hi Malcolm,
I haven’t come across that, or had any experience with it. I’m not even sure when you would apply it (to kill the wasp or prevented infection?).
If anyone else has any experience with this, we’d love to hear from you!
Happy Gardening!
Duncan
I am curios to know if wrapping a gall tightly with some sort of tape of thick fabric would prevent the wasps from emerging? the tape could be removed from mid summer until the end of winter, allowing the branches to grow etc. Would it work or would it hurt the tree more than the wasps do?
Hi Anja,
A few people have floated this idea to me now. I suppose that it may work. However, I’m not sure that all the effort would be worth it. Far better to focus your energy on prevention of infection (or re-infection) rather than emergence. If you do give it a go, please report your findings back to us. I’m sure I’m not the only one who would be keen to see how you get on.
Good Luck and Happy Gardening!
Duncan
I’m getting exited folks! I painted my citrus galls with acrylic house paint with 10% neat Confidor mixed in. I’ve just dissected a couple and didn’t find anything wriggling or looking anything like a wasp preparing to eat its way out to freedom. I’ve also noticed that there was no discernible increase in the size of the galls since they were painted in early autumn. Proof will of course be the lack of emergence holes but it’s looking very promising. I did two coats a couple of weeks apart and I’m hopeful that the very small actual quantity of Confidor will not be a threat to bees. If it’s likely that I’m mistaken on this point please let me know and I’ll wrap the treated areas in aluminium foil to ensure they aren’t harmed. On the subject of foil, has anyone tried a few layers to blunt the dentition of the nemesis? It was on my list of things to try before I decided on the Confidor paint.
Hi David,
Thanks for sharing an update on your trials. I opened up some galls the other day and the larvae were looking quite small and undeveloped still. So I’d say you’re still a while off confidently being able to say it works. Please keep us all updated.
Good Luck & Happy Gardening!
Duncan
I have the gall wasp scourge on my lemon and lemonade tree
You’re certainly not the only one Tony. Here’s hoping your tree is productive despite the wasps.
I’m from Adelaide, my native limes are much more affected than the lemon trees in my garden.
The yellow sunrise lime is much less affected than the red finger or desert lime
I have only found one or two in the navel orange, none in Japanese seedless mandarin or tangello
I haven’t found them in the Tahitian lime yet either
When I see the galls I remove them.
By doing this on a regular basis the structure of the trees are preserved
The wasps prefer the newer lower branches
Thanks for sharing your insights Rod. Very insightful.
Good Luck & Happy Gardening!
Our lemon tree has so many galls on it that it seems impossible to cut them all out without cutting down about 70% of the tree. Should I just do this or try to cut out the larger ones? The tree does not produce as much fruit as it used to. Also is it too late to do this in October/November or should I wait until next June? Thank You
Hi Julie,
I’d remove as little of the tree as possible. If you are determined to cut it back, then I’d do it in a month or so. This will mean any flush of new growth will occur after the wasps emerge (last year they emerged in late November). Our citrus gall wasp experiment has so far shown that the biggest impact on fruit yields are how well fertilized the tree is. Perhaps focus on feeding the tree rather than cutting it back?
Good Luck & Happy Gardening!
Duncan
Hi there
We have a 6 x 6m backyard and I would class us as completely novice gardeners. We have a lime tree, that fruited well in the first year, but nothing for 4-5 years after, and this year we noticed the woody lumps. I have finally got around to doing something, which involved using a hacksaw to remove the branches. I then google and find this site. Lots of great suggestions, and I have put the ‘hacked’ off branches into a bucket water to kill the little blighters.
Great site!
Thanks for the great feedback Daryl.
Good Luck & Happy Gardening!
Is it okay to just cut off branches anytime of the year? I have been cutting off the the infected branches as I find them, also cutting into small pieces, hopefully distroying the egg’s
Hi Robyn,
as I advocate in the blog post, cutting branches in winter stimulate a flush of new growth. This new growth is particularly attractive to the wasp. So I would avoid pruning in winter.
Good Luck & Happy Gardening
Duncan
Just as anidea Duncan, how about pruning off the gall lump or whatever you call it. Clean up the branch and then graft it back on. Could that work? I have almost pruned one of my trees to death clearing out persistant gall wasps in the past and am just wondering if this is a better way forward. Also how or what is the best way to such a graft?
On fertilising I am thinking we are feeding the soil first and foremost so would it not be better to fertilise in small amounts frequently over winter to have really healthy soil biology. Tha way when the tree enters spring it isnt to a burst of nitrogen but rather a nice heatly availability of balanced minerals if and when it wants it hence maybe that will result in less of a burst out of new branches but rather slower growth. All theory but just maybe a way forward?
Hi Miro,
Whilst I like the idea of grafting branches back on, it’s just not practical on a large scale. Citrus trees are a little more challenging to graft that say apples or pears. So it won’t be of much great benefit.
You are spot on with regards to fertilizing. A little often keeps nutrients levels more consistent for the trees.
Good Luck & Happy Gardening
Duncan
I am trying external surface spray on the branches as it last for 3 months but I worry about the toxicity to bees and other insects. There must be a way to combine something with petroleum jelly to put on the falls to do the job.
Hi Tim,
The surface spray will definitely have an impact on bees and other insects. I definitely wouldn’t recommend it. The kaolin clay is showing promising results and would have far less impact on your garden ecosystem.
Good Luck & Happy Gardening
Duncan.
A couple of weeks ago I wrapped the galls with clear medical tape which sticks together nicely. At the time I was seeing a few live wasps on the stems. I can now see wasps that have emerged under the tape but are stuck to it. My lemon tees are in pots and at head height so it was easy.
Thanks for sharing your experience Helen. Could be useful on small trees but very fiddly on large trees. I prefer the convenience (and low environmental impact) of Kaolin!
I have just removed a heap of new galls. I regularly removed all galls so these are new since November. There were a lot with a couple of escaped wasps 🙁 The old August emergence myth seems to be just that. It appears that the galls grow at different rates and I’m not clear when the wasps actually emerge. Any ideas please? Thanks
Hi
I have already removed all the galls I could seen by November on the citrus trees. Last week I discovered a lot, particularly on the Meyer lemon. Unfortunately a couple had escaped already. It seems to me that the old idea that they hatch in August doesn’t apply here in Melbourne. In addition, these galls had grown rapidly to get quite large between November and the end of December. Would appreciate your advice. Cheers Jon
Hi Jon,
As per the article, we agree, the wasps don’t emerge in August but late November or early December.
Please keep us updated with any other observations you make.
Duncan
How are your experimental trees going?
Hi Melanie,
Thanks for your interest. Next week we will be performing our “prune in June” on the relevant trees and then putting together an update after that. The trees are looking great and are all covered in ripe lemons regardless of their gall wasp status.
Stay tuned and thanks for your patience!
Duncan
Question. Has anyone noticed wasps emerging yet in Melbourne? If so, this forum could become a log of wasp emergence dates. I have galls wrapped in aluminium foil, the galls have grown but wasps not yet emerged from one which I unwrapped today (17 January).
A couple have escaped but there were lots more big galls that grew over December (which I cut out). It certainly puts the lie to the old saw about them emerging in August!
Hi Graeme,
Our gall wasps started to emerge on December 2nd and many people in Melbourne had them emerge around the same time. They continued to emerge over a prolonged period of several weeks. That being said there are many galls on our trees with undeveloped wasps in them. I wondering if they were eggs that were laid that we’ren’t fertile? Of if they didn’t develop for some other reason.
Thanks for the great suggestion of logging the gall wasp emergence dates. We’ve been collecting a lot of data from grower’s posts to our Facebook Page.
Good Luck & Happy Gardening!
Duncan
Hi , I grow citrus in Melbourne, and find that mandarine, Tahitian lime and lemon are all affected by gall wasp and then by leaf miner later in the season.
Thanks for sharing your experience with us Jenny!
Good Luck & Happy Gardening.
Further to my question on Jan 17th, Yesterday 20th, I looked at a friend’s infected tree in melb sth east suburb and wasps had not yet emerged. Any dates I find on various web sites all indicate emergence in late spring so maybe Melb’s climate causes a late emergence?
Anyway I, and probably others, may be interested in the actual dates please?
I found live gall wasps emerged inside sticky tape I had wrapped around the galls. This was well before christmas. There is no sign of them now.
I love that you are undertaking this experiment with the gall wasp. Can I suggest another option to add to the line up which is to scrape away at the gall that results in exposure of the eggs to the air and kills them. My experience is that there is no detrimental effect on the limb of the tree as the scraping is not deep enough to interfere with sap flow.
Hi Sharyn,
Thanks for the suggestion. We have had similar positive experience with this treatment technique. However, this trial focuses on preventing the gall wasp from infesting the tree in the first place, rather than labour intensive treatments.
Good Luck & Happy Gardening!
Duncan
I have a cumquat that is infested with this pest in Glen Iris. I thought I’d pruned it all out, but after what seemed like a year pest free I noticed the other day the galls are back. I also have a Tahitian lime that has had the problem ongoing for a number of years.
I will try the suggested regime and see what happens.
Thanks for sharing your experience Julian. Please keep us all updated on your efforts.
Does cutting slithers off the Gall help? I’ve tried on my small infected tree and it seems to dry the lump out and open up the holes. If nothing else it feels good thinking it’s getting rid of them.
Hi Jason,
Cutting slithers off the gall (eg with a potato peeler) can help dry the gall out. This kills the larvae inside. However this strategy only treats the symptoms. We’re focusing on preventing infestation in the first place using the kaolin and feeding strategies.
Good Luck & Happy Gardening
Duncan
I have two small lemon trees Eureka and a Lisbon. I have made a paste with Kaolin clay and water and painted the galls with this paste on the trunks. I don’t know if it is working but there doesn’t seem to be any Gall exit holes.
Hi Maree, we use the Kaolin clay in late November and early December. The aim being to stop the galls landing on the new growth and injecting their eggs under the bark. Kaolin itself, is inert so it will be interesting to see if it has an impact using your method. Please keep us all informed.
Good Luck & Happy Gardening!
Duncan
I’ve bought a couple of citrus trees, they are on most except the lemonade tree, strange…
They do seem to have preferences for some varieties over others. Thanks for sharing Michelle.
Thank you – so if there are galls on the tree and you use the kaolin to stop more activity, does the existing gall tissue gradually disappear over time.
Duncan,
Have applied your methodology in managing the gall wasp issue for the last 18 months to 2 years with great success. I have a Tahitian Lime, Myer & Lisbon Lemon trees. Note though the gall wasp problem has note been eradicated but is under control. The historical gall swellings don’t pose a problem and if new swellings appear they are quickly dealt with be using a vegetable peeler cutting one side of the gall. Note all citrus plants I have seen in Melbourne (even cumquats) have the gall wasp problem. If you don’t have the issue your lucky.
Thank you Duncan for your advice.
Chris Torr
Thanks for the great feedback Christopher. I’m glad that it is working out for you.
Hi, I have recently taken over theosition of coordinator for the Yarra Glen Living and Learning Centres garden, and we have citrus trees with gall wasp problems. The trees are fairly young about 3 years old. As they form part of our edible garden, I would be grateful for your advice. I recently fed the garden with a general purpose long acting fertiliser. Our funding is minimal but i still need to do what ever i can to fix this problem.
I also need advice on prunu g a couple Apple trees to aspalier them along wires. They have not previously been trained at all. They are probably 2.5 mtrs in height and fruited well last year. Will pruning these trees back to aspalier them cause any problems?
Hi Carolyn,
As per the article itself, we advocate for not pruning in June, limiting fertilizing somewhat and perhaps trying the Kaolin Clay treatment in Novemeber.
It is difficult for me to give you advice on the espaliered apples without seeing them. However, in principle this should be fine. I would perhaps do this as part of a summer prune, rather than a winter prune though.
Good Luck & Happy Gardening!
Duncan
Hi, I am interested as I was not satisfied with all my methods. But mainly my conclusions are:
. Eco oil spray routinely on all new growth without exceptions.
. Organic, slower feed eg manures and only a light chemical food dressing
. Slicing newly found small growths and cutting out large growths
. Don’t let trees grow too large.
Thanks for sharing your experience with us Alex.
Good Luck & Happy Gardening!
Thank you so much for this information. I live in Lockridge WA and this area and the surrounding suburbs are the areas most affected by this pest. I have given up on my grapefruit and lemon as they were the most affected but have kept my mandarins, lime and orange. I am going to try some of the methods you have recommended and see what happens.
Thanks for the great feedback Moira. Good Luck with the strategies. Please let us know how you get on!
this post is really wonderful and thank you so much.
i wish you all the luck in your experiment. i have also observed that they dont touch the cumquat and cumquats are such pretty trees.
And that they dont attack an orange tree that is not ‘flushed’ in new growth. they love my budda hand lemon! i cut them out but as you noted it does seem to upset the tree.
i have often wondered how to cover the galls to prevent them hatching but i haven’t thought of something to use. i thought about wax but that has its own issues – ie it would need to be hot to paint onto the galls and thereby burn the tree – but it might work. and then the bees might come hehehehehe. the potato peeler is a good idea!
Of course the other big issue is the fruit fly. its very disappointing to see that even in areas like shepparton there is no great enthusiasm to eradicate it. I think that its a problem that also needs a ‘brains over brawn’ solution so maybe when you have beaten the wasp you might turn your attention to the fly!!
Thanks for sharing your experience with us Maree. Yes, we will happily turn our attention to fruit fly as we sort out the gall wasp problem!
Good Luck & Happy Gardening!
Duncan
Wrap the gall loosely!! with aluminium foil and secure with insulation tape.
Hi Graeme,
This like many of the other suggested methods this seems like a lot of hard work – especially on a large, heavily infested tree. Plus it doesn’t prevent the tree being infected from wasps that have emerged from other trees. The kaolin clay prevents infestation in the first place.
Happy gardening
Duncan
If it is a native pest surely there are biological controls? It would be in the interests of “backyarders” and commercial growers (which there must be all over Victoria) to identify these biological controls and test them? Do we know what the state Dept. of Agriculture is doing about the problem? Have they any recommendations beyond cutting out the growth affected by the gall wasps?
Hi Rob,
Yes there are biological controls (small predatory wasps) that are released in Queensland where the gall wasp originated. However these natural controls don;t survive Melbourne’s conditions. Other than around Mildura, there’s not a lot of commercial citrus growing in Victoria, so I guess the state Department isn’t as interested in controlling the pest in Melbourne. It would behave very differently in Melbourne vs Mildura so control mechanisms would need to be altered. NSW DPI and our research show that the Kaolin clay treatment may be the best control method for Melbourne based trees.
Good Luck & Happy Gardening!
Duncan
Just discovered your informative website today after spending 4 hours cutting out branches infected by gall wasp on my Australian lime and Lisbon lemon tree. But after reading all the comments I realise now it was the wrong time to do it!
They were heavily infested and I now have way too many prunings to do the ‘soak in a bucket of water’ method or even to put in a plastic garbage bag so not sure how I’m going to get rid of them.
However I’m wondering if there is any point in getting rid of the galls at all. Are we getting our knickers in a knot for no reason? Maybe we should just leave them. My citrus trees are over 25 years old and have been infested for over 5-8 years now with no signs of reduced fruit quality or number nor reduced vigour of the trees. This is the first time I have done anything about them. (Persuaded by a friend that I must!) I also have two large orange trees in the same area which haven’t been infected at all. I don’t fertilise much at all but if I do then I use aged chook manure.
Some great observations that you’ve made there Judith. They’re very much in line with what I am thinking.
A more relaxed approach is certainly preferable to “getting our knickers in a knot”!
Good Luck & Happy Gardening.
Duncan
Duncan,
I really like this thread as it brings up some interesting ideas.
While I appreciate that you are in favor of preventing the gall wasps rather than the treatment of infestations, one can’t help to think that if there is treatment of the gall wasp infections and after a number of years once they have completely taken over a citrus tree (including very old established growth rather than the new growth), they are much more likely to try to find other trees to infect. The tree I treated was dying after it was >90% infected and neighbours were noticing an ongoing infestation over years.
In my mind if you don’t treat the galls by cutting them out, treating them with Gall Wasp Guard, peeling the infected area or one of the inventive measures mentioned in this thread, they are going to increase in number and look for other trees nearby to infect. New growth might be favoured but even at my place where I had branches established 2-3 years ago, these were infected.
I see the lack of treating the infection as increasing a cycle of infestations in the future, so the preventative measures are equally important to the neutralization of the gall wasps.
I would expect that if most folks were dilligent about pruning out infections, there would be less infestations and eventually the cycle might be at a level where there are very few branches that need to be cut out.
Also, I think a couple of contributors have asked a similar question but I couldn’t find an answer.
Are you able to point me at a website which shows me how much Surround do you mix with how much water and what sprayer works to spray the solution of Calcined Kaoline Clay?
Hi Roland,
Interesting views on treatment rather than prevention. Perhaps both strategies would be more beneficial in reducing numbers. However, applying treatment methods will likely reduce crop yields. The wasp is here to stay, we will never eradicate it. Hence my focus on prevention.
As for mixing the kaolin, a few spoonfuls in a 5 litre sprayer is plenty. As long as the leaves turn white when sprayed you are on the right track.
Please keep us updated on progress
Duncan
I moved to our place 3 yrs ago and have 3 lemon trees in my backyard. Two of them have some lemons . The third one doesn’t do anything.The first two have flowers and fruits.Every brunch with fruits or flowers is infected. I tried to cut off infected brunches and close the holes with some paint but big holes appeared in paint bloches and looks like it didn’t work. We even had them, those wasps, attaching their nest ( like honeycomb looking) on out timber fence.
New shoots don’t have infection.
When your trees or brunches are infected, are they effecting fruits? Are these fruits ok for consumption or they are infected as well?!
Regards
Hi Bonza,
Galls wasps do not infect the fruit or affect the quality. They are safe for consumption.
Good Luck & Happy Gardening!
Duncan
Really interesting. Our lemon tree is more wasp nests than tree so we don’t even try to cut them out. We’re also strict practitioners of Darwinian i.e. survival of the fittest – little or no intervention from us. We don’t feed and fruiting seems to depends only on how much rain we get. Overall the tree is pretty healthy.
Thanks for sharing your observations Andrew. I love your approach to gardening!
Duncan
I smeared tree guard over the galls on my Tahitian Lime Tree, hoping it will prevent the wasps from emerging. Is this the correct thing to do as I am trying to espalier my tree and cant afford to chop off any significant branches as the tree is only in its second year of growth.
Hi Helen,
We haven’t tried this ourselves. We focus on prevention of infestation in the first place, rather than treating the galls once they have appeared. You could also try using a potato peeler to remove the bark off some of the gall (but avoid completely ring-barking it).
Good Luck & Happy Gardening!
Please keep us all updated on the outcome.
Duncan
i FOUND YOU HAD TO CONSISTENTLY PRUNE OUT THE GALLS WHENEVER YOU FOUND THEM REGARDLESS OF THE TIME OF YEAR. LEMON TREES ARE TOUGH.kEEP THE WATER UP AND REMOVE ANY DEFORMED LEAVES ALSO AS YOU FIND THEM. Invasive roots from surrounding plants are the biggest problem and by providing a strong environment, you incline the tree to be vigorous and resilient. Get your other basics correct . 1. the rhizome layer (where the Magic happens ) Well-drained soil raised from surrounding soil levels with timber border of at least 100mm, preferably 200 mm. Build your soil with organics, mulch and a top cover of decomposed bark. This provides gravity-powered osmotic and capillary drainage and soil humidity at the same time .. Self-regulating at no additional cost. Keep weeds and invasive root systems clear of your root ball and root system -generally about 3-4 feet radius is critical .3, Water and fertilizes when necessary, 4. put some rusty nails and scrap steel under the mulch layer – spread it out, works very slow release .5, steak or tie up trunk till 5 x years old -well-rooted by then , What has all this got to do with Galls ?PLENTY. gIVE A CITRUS A STRONG STABLE GROWING CYCLE largely self-sufficient and you build resilience to stress factors so when they occur, the tree can respond. Listen to your tree, understand its language and that of its microfauna in the soil and you are on the pathway to healthy gardening and living. So prune galls off, remove attacked leaves and follow any other common-sense approaches. nA good brew wee on them does not hurt either . happy Gardening.
I live in Adelaide & have 1 mandarin, i grape fruit & about 20 varieties of kumquat. All the cumquats types are now effeted real bad, a few unique specimens so bad that I think they will have to be destroyed. Relatively, the mandarin is completely unaffected & the grape fruit has been hit in a few locations. But really, it is nothing compared to the cumquats [which I love] & am greatly saddened that while I have experimented with non noxious glue etc.& some may survive from this, there is no doubt that some will have to be completely destroyed [& 1 such example has a unique, longitude, double leaf & is a nangano.
All the best
Hi Tim,
Thanks for sharing your experience with us. Hopefully you manage to save the cumquat trees.
Good Luck & Happy Gardening
Duncan
Given that June pruning is not encouraged, what about Spring pruning ?? I have a lemon tree which I’m guessing could be 20 years old with gall wasp and is currently full of fruit and is also full of blossom and new growth. It is currently too tall so I need to prune it back to a more manageable size. I was thinking that it could be a good idea to do this shortly, before it gets too hot in Melbourne (north eastern suburbs) with the ‘bonus’ of removing the much loved green wood that the soon to hatch gall wasp finds so attractive…. your thoughts would be appreciated.
Hi Chris,
That would be a great idea. The tricky part is getting the timing right. Too late in the season and you miss out on a crop of fruit next year, and risk sunburn on the newly exposed branches. Too early and the tree will put on a flush of new growth and be very susceptible to infestation this summer.
Please keep us all updated on how you get on.
Duncan
I grow citrus in Melbourne and found this interesting article similar to my experiences managing gall wasp. My old but productive lemon tree is heavily infected with gall wasp. I skeleton pruned it once on recommendation and found all the new growth was rapidly recolonised with galls.
These days I prune the old galls and dead wood and some of the extensive new galls. More pruning would result in loss of fruit.
Occasionally galls infect my orange trees and I notice they have a more detrimental effect often causing the branch to become brittle and die.
To control galls in young oranges and limes I scrape the sides with a vegetable peeler to expose the cells inside which then kills the gall but does not harm the branch.
Some great tips there Maggie. Thanks for sharing your experience with us!
On the advice of one of Bunnings people, I have sliced off all the galls on my just established and espaliered dwarf lemon and lime trees. Didn’t have enough branches to take it any further. I have bought some sterile spray for the pared back wood, but she suggested to let the heat and sunlight kill the open galls, and not spray. I’m worried about infection: some of the branches, which are only around 2 centimetres in diameter, are now half denuded. What do you recommend?
Hi Beth,
As per the article, I recommend not pruning out the branches/galls in the first place. Common practice nowadays is to leave any tree wounds open to dry out. Sealing them only seals in the fungal infections and in time can lead to the trunk of the tree rotting.
Good Luck & Happy Gardening!
Duncan
Until last July 2019, when we moved house, I had a lemon, kafir lime, grapefruit and cumquat tree and finger lime. The lemon and kafir lime both suffered with gall wasp, the grapefruit, finger lime and cumquat did not.
We are now 2 km north of our previous home and the lemon tree existing had severe gall wasp. I maybe foolishly pruned it down to two bare branches/trunk. It has put on numerous “branches” which I will attempt to thin out and keep the tree in check. I have brought the finger lime with me as it was in a pot and acquired a kafir lime Tahitian lime and cumquat so fingers crossed!
Good Luck with the citrus trees Chris. Please keep us updated on progress.
Duncan
Morons. Continue pruning, with a focus on slicing and aerating the spots of infestation rather than complete branch removal. ONLY ON A NEEDS BASIS. Gradually persist and ensure no galls hatch and keep in mind the overall health of the tree. Always water and fertilise. The process needs three (3) seasons, after which time the tree will be hall free. You need to learn and observe how the wasp lays (with hall) [get it?] And the younger the tree is relevant. One needs to understand the impact of just one laid immature larvae.
Thanks for the enthusiastic feedback David. I think you may have missed the point of the article though.
Have you considered covering the tree in fine netting during October and November?
Hi Chloe,
That’s a great idea. It would need to be very fine netting and the tree would need to be completely free of existing galls, but it might work.
Thanks for sharing
Duncan
I would like to know whether anyone has tried painting the swollen gall egg area with ‘Tar’ I’m wondering if this would stop them coming out of the branch
Hi Trevor,
Great idea! However we’re focusing on methods that prevent infestation in the first place, rather than treating symptoms once they appear. Please let us know how you get on if you do give it a go though.
Good Luck & Happy Gardening!
Duncan
I have been trying the Vaseline after being advised by a friend. You need to keep doing it I think over time because it seems to ? soak in or removed by rain. The gall is like a sausage on a stick this year and seems to prefer a south east view. Hoping it has some effect.
Hi Val, thanks for the update. It makes sense that the Vaseline will disappear over time.= and need re-doing. Sounds too much like hard work to me! Please keep us update on the effectiveness though.
It was so satisfying to read this! You have listed everything I have thought and learned as a gardener but didn’t know how to put into words. I tried the ‘cut the galls out’ method and what did I get? A dead stick lime tree in a pot. Then with my lemon I cut off the galls that were on small branches which could be pruned easily (and I DID NOT do this in June, as that is not the time to prune a lemon). Then where there was a big bulbous gall in the trunk which could not be removed without damaging the tree – I partially sliced into it, allowing oxygen into the gall and that didn’t hurt my tree AND seemed to actually kill off the gall. I’m now dealing with a mandarin tree in a pot that has gall and other issues and this post helps me to know that I will treat the other issues and do what I can to the gall without going the full hog and killing the tree in trying to deal with the gall. The best part about this post is the admittance that mechanical pruning by a few gardeners is not going to rid us of gall wasp. It’s hear to stay so we have to garden around it, not against it or we will kill off our trees.
Hi Jess,
Thanks for the great feedback and for sharing your observations. Glad you found the article useful.
Stay Safe & Happy Gardening!
Duncan
Greetings,
My name is Tim & I have a lime, [that is planted alone & so far has no gall wasp], a mandarin, grapefruit & 22 cumquats of different sub species, some of which I have grown from seed in the hope of obtaining a sport!
I see you have stated [as indeed many others have similarly], that they have never seen gall wasp in a cumquat tree & some have stated they believe the cumquat is immune. It isn’t! I have one enclosure with the 2 other named citrus & 3 or 4 cumquats in the same enclosure! The mandarin & grapefruit were heavily infested, 2 of the cumquats were almost as badly effected & in fact 1 was so bad, I did not think I could save it [a nangano]! I am still struggling to save it after almost 2 years. Because I have separated& spaced my remaining cumquats, i have had little problem with them. For your information I seem to have got completely on top of the situation by 2 exercises [I believe in continuing to fertilze cumquats year round]:
1 In new, greener growth where smaller stems reach out from the main stems [a favourite location for gall wasp, you tell by a dryish appearance or spot that gall wasp have already visited. I just pick them off with the nail of 1 finger until I see no more! The same is applicable along the main, greener stems. Once a year I usually spend a sunny afternoon sitting on an old milk crate performing such function & this exercise is [in my experience], 100% effective.
2 When core wasp is well established [as I original found them] & particularly so with the mandarin & grape fruit + 2 accompanying cumquats, I noticed the huge galls & ugly aftermath & decided to do something different. I purchased small brushes & normal office glue from ‘Office works’. Some state they contain no dangerous chemicals & others don’t, but the employee stated because glue is a favourite with children, by law, the glue cannot contain dangerous chemicals in case it is swallowed. In the end I took 1 of each product & painted the effected branches; I was hoping it would sufficate the larvae or otherwise tempt them to leave [out of season to die]! To my surprise nothing happened! The thickened wood remained that way without the nasty holes that renders the trees so ugly & this havs not changed after about 2 years. In my view, they died before they could course damage & the thickened branch makes the tree appear more sturdy! The only downside with this 2nd method is rain! It tends to wash the glue off. Therefore, everything requires reglueing! But if one can temporarily place a plastic sheet over the tree [or better still suspend same over the tree], the glue does not require retouching! If the cumquats are in large pots, I also have trolley to place them under a carport! This also works very well indeed & no ‘repainting’ is required!
[ps I periodically look for signs of anything attacking my cumquat trees. I absolutely love the nanganos which are by far my favourite fruit [but many people don’t know that cumquats should be eaten with their actual skin & contents simultaneously! I eat all varieties that way, even the most tart as the skin is always the sweetest part of the package & should also, always be included when making marmalade!
I hope I have been of some assistance, & I wish you & everybody else, all the best’
Kind regards tim milton, empiricism27@tutanota.com
Hi Tim,
Thanks for your extensive comment sharing your experience and observations. Sounds like you’re doing a great job.
Good Luck & Happy Gardening!
Duncan
I have a small Myer lemon. Last year I sat
down with a vegetable peeler and large pin. I
peeled the skin off each gall and dug out or
gouged the wasp egg cell. It seemed to work
and there is little gall on the tree now. There are
no other citrus trees close by which helps.
Do you think this method works or is it my
imagination ?
Hi Margaret,
It certainly seems to work in that you kill the wasps in the tree itself. However, it is a treatment and not preventative like the methods we are recommending. Especially if there are other trees nearby (which you don’t have). I can’t imagine trying that technique on a large tree full of galls! However, it’s worth a shot on smaller trees.
Stay Safe & Keep Gardening
I seem to have missed the point in this conversation?
If all of us citrus fruit growers or tree owners, did as Margret suggested for just three years in a row, that would be the ultimate prevention!
I’ve used the peeler method and spray fortnightly with Neem oil, and have just ordered Kaolin Clay to spray just before they hatch this year. The fight continues! Love the blog..
Hi BE12XL,
Thanks for your comments. The problem with your suggestions are as follows:
– The wasps are native to northern Australia and are hosted in our native finger limes
– They have spread right down the east coast and over to Perth
– Not everyone will be on board with your suggestion so elimination is unlikely eg from rental properties or where folks haven’t identified the “problem”
– Even if we do eliminate them from say Melbourne, they we quickly recolonize from our native limes growing wild across the country
Good luck with the Kaolin!
Duncan
My 20 year old lemon tree became so badly infected with gall wasp that I had it cut back severely in June last year, and it looked like a leafless pole. In late spring signs of new growth began appearing, and over the summer tiny new leaves developed. As autumn approached I was worried that any frosts might damage these, so I put a large black garbage bag over the tree. When I removed the garbage bag some weeks later I was amazed to find it full of shiny black ants about 1.5cm in length. Can you tell me what these would have been, and would they have damaged the tree. I have since purchased a gall wasp trap and hung it from the branches. The growth of the new foliage has absolutely amazed me, and how long will it be before it produces any lemons?
Hi Yvonne,
It’s hardy to identify the shiny black ants without identifying them. But they are probably as you say, ants! They wont damage the tree, but were probably “farming” aphids or scale. It’s a sign of a tree in distress, usually a good feed will fix it.
We don’t recommend gall wasp traps as they also catch beneficial insects. If you were to use them, then only put them out for the few weeks that the wasps are emerging in late Nov and early Dec.
In Melbourne citrus fruit take at least 12 months to develop and ripen after flowering. So you’ll have a better idea once the flowers develop.
Stay Safe & Happy Gardening!
I have a heap of mulch that obviously included a lemon tree that was infected with Gall Wasp.
The mulch is now 12+ months old.
Can anyone advise if it would be free of ‘live’ Gall wasp yet?
Hi Mike,
I would guess the wasp larve would have died within weeks, if not days of it going through the chipper. Although that’s just a guess!
Stay Safe & Happy Gardnening
Using a scalpel blade on the gall wap affected area has worked. Scoring apparently disrupts life cycle of wasp and they don’t hatch. You can see this because there’s no tell tale exit holes from emerging wasps and the tree doesn’t appear to be bothered by the scoring (perhaps a half mm deep).
Hi Lachlan,
Thanks for sharing your observations. Many folks are recommending similar actions with eg potato peelers (as are Gardening Australia). However, on a big tree it is time consuming and only treats the symptoms. I’d rather focus on prevention in the first place.
Stay Safe & Keep Gardening!
Duncan
I have small green lemons about 15 mm diameter, and on some, the stem on the twig/branch has greyish lines on some,tiny but visible, not green up to the fruit, I am tempted to sever these short fruit stems now. I have coated one big gall with silicone in an effort to stop them emerging, is this ok?
Hi Graeme,
Without seeing the tree it is difficult for me to comment. As for the silicon, I personally wouldn’t bother. Lots of folks are recommending similar actions, but it is time consuming and only treats the symptoms. I’d rather focus on prevention in the first place.
Stay Safe & Keep Gardening
Duncan
Good article. Please fire your editor as the first apostrophe in the following sentence is incorrect. It is also annoying and distracting. Observations is simply plural. No apostrophe is required.
“Observation’s I’ve made when growing citrus”.
Hi Mick,
Thanks for the brutal feedback. We won’t be firing our editor, who volunteers their personal time to review all the blogs and newsletters. Instead we’ll just quietly update the blog and hope that you’ll be a little more subtle next time.
Stay Safe & Happy Gardening!
Duncan
Good time to prune Lime tree due to knots or swelling caused by Gall Wasp in Melbourne?
Hi,
As per the article we don’t recommend pruning the galls from the tree.
Stay Safe & Happy Gardening!
Nice, Duncan, well said.
I saw a method on tv this lady was doing about the branches becoming fat because of the wasp where it lays it’s eggs she said take a sharp knife or potatoes peeler and go down the branch or potatoes peeler and expose the eggs and go a bit deeper with the potatoes peeler and scrape down the infected branch and she said the air will kill them.
Hi Yvonne,
Great tip. Unfortunately, this method does;t prevent re-infection. The kaolin clay seems best for that.
Good Luck & Happy Gardening!
Duncan
What do you think of Gardening Australia’s advice to ‘potato pe’ the gall out?
My trees were so infested that I had to drastically prune today, I had previously potato peeled but the nuber of galls still there infected all branches of my lemon and my ‘fruit salad (grapefruit, lime, orange and mandarine) tree. All fruit type branches were impacted on the fruit salad tree. I also have 2 oranges, a cumquat, 2 pomelos and a double lime in pots with the infected lemon but they were untouched. I also have 2 finger limes, they also weren’t touched. Am in Melbourne.
Hi Karen,
The problem with this method is that it doesn’t stop reinfection. All it does is treat the symptoms. The kaolin clay method seems much better at preventing infestation in the first place – plus it is not as time consuming if you have a big tree!
Good Luck & Happy Gardening!
Duncan
All this is quite silly and pseudoscience sucked off left thumb.
To stop adult gall wasps from reinfecting your lemon tree you have to
spray your lemon tree every fortnight with a mix of white petroleum oil
and comfidor during the wasps hatching period. Personally in Melbourne
I start in late August if temperatures raise above 20C and continue till mid
November. You may fertilise whenever you want. And I have cured my Lisbon
lemon tree, get great crop and no more Gall Wasp problem!
PS. Eco oil is not good substitute for white petroleum oil in this case – wasps
hate smell of petrol and don’t lay eggs and the spray stays longer light rain.
Hi Richard,
Thanks for the feedback. However, some of us prefer to take am more organic approach to gardening.
Happy Gardening!
Hi, I’ve hung up sticky traps in the dwarf varieties of lemon and lime. Then, to ensure I don’t trap native bees and other good bugs I’ve covered the lot with netting. It is the type of netting that bats and flying foxes don’t get caught in; holes are tiny and the netting is white. I hope this also prevents the wasps on my trees from escaping onto the neighbouring trees. It may reduce pollination of blossoms but that will be okay for one year if I can get the wasps controlled. It seems to be working. The sticky ‘poles’ are getting more and more tiny black insects stuck on them. I’ll leave them like this for a couple of months. I also scraped open as much of the galls as I could without ring barking the branches. That would have also reduced wasp numbers.
I have also thought about wrapping the galls themselves with insecticide soaked bandages. As the little blighters chew their way through they’d have to eat some of the bandage. I haven’t quite worked out the mechanics of it yet though. Maybe I’ll try those cut to size, sticky bandages and soak them with insecticide and cover the trees again. Cheers, Helen
Hi Helen,
You’ve clearly put a lot of thought into this. It might be worth looking into the Kaolin clay that we trialed in the gall wasp experiment. We are seeing the best results with that so far.
Good Luck & Happy Gardening!
Interesting didn’t realise we had them until a friend was discussing problems with her lemon tree, when we looked at ours we found the woody growths. I and noticed over the las few years when I had located a home made Fruit fly bate in the lemon tree that I caught a lot of what looked like small fly or even black fruit fly (bit similar to look at?) The bait must have been working our trees weren’t super infected but I stopped the bait and started using netting against the fruit fly which I found very successful; – might put some traps back in the citrus trees and see if I egt the wasps??
Hi Ian,
Glad you found the blog post useful. Please let us know how you get on with your traps. Just keep in mind that the traps are likely to also be catching beneficial insects.
Good Luck & Happy Gardening!
Duncan
FYI – today I saw a single gall wasp in my Meyer but I have found no new exit holes. Is this a normal date given dates that in other years emergence is more lilely to be November?
Hi Graeme, I sent you an email about this back in Oct, but didn’t receive a response. That emergence seems very early for Melbourne. Which suburb are you located in?
Just to confirm….I am now seeing lots more adult wasps in my meyer, emergence date is here!
I use a fruit peeler to shave off the gall wasps to expose the larvae/eggs in late Winter and in early November (new bumps). The larvae dies naturally when it is exposed to air. My lime tree that I shave in winter flowered profusely in Spring and I can see tiny limes. I anticipate lots of lime in Winter 2021.
Thanks for the tip Katherine, it has become a popular one since it was featured on Gardening Australia earlier this year. The problem with this is that it is a treatment of symptoms/infestation. We would rather focus on preventing infestation in the first place. The kaolin clay we have investigated in our experiment seems to show the most promising results so far.
Good Luck & Happy Gardening!
I notice gall wasp on my Tahitian lime and lemon trees today (1/Dec) in north east Melbourne. I monitor my trees almost daily since i’m working from home and have no galls so they must have blown in from neighbouring properties. Have sprayed with citrus oil to prevent them flying off and then rubbed them dead with my fingers. others please watch out for them as they are now active/emerging in the cooler Melb suburbs
Thanks for the update Amy!
Very interesting reading .Hope to learn much more
Glad you found it useful Robert!
I trialled kaolin spray- mix kaolin clay with water and liquid soap:
1 litre will be
110 ml clay
888 ml H20
2 ml liquid soap
& is enough to generously coat multiple trees.
Repeated several times weekly.
Easy to gently rinse off where you don’t want it.
No emergence holes from any galls. It appears to have been highly effective.
New growths and flowers also seem stronger.
Will do this again next year.
Melbourne’s Northern Suburbs
We have a 20 year old at least lemon tree in our yard that was pruned for galls around 15 years ago, and in a period where we were renting the house a tenant hacked up the tree to make way for a mobile home which we had no clue about until recently. I’ve started trying to care for the tree & at some point am going to try and prune all the galled branches though at this stage there may be no saving it. If June’s a bad time to prune can I just do it sooner & get it over with? Also, I took trimmings from the tree to try & propagate. I did my best to take them from non-galled branches but what is the risk the trimmings might be infested?
Hi Stephanie,
You can prune it at any time. There’s just consequences of doing so. Pruning in winter or early spring will result in a flush of new growth that will be prime gall wasp infection sites come December.
Citrus trees are normally propagated by grafting. If there are no galls in the material you selected then it is unlikely that they contain gall wasp larvae. However, note that these cuttings can easily be infested by galls from another tree in summer.
Good Luck & Happy Gardening
Duncan
We’ve been in our new home only about 11 months now and the resident lemon tree has been prolific with its fruit… still cropping with new fruit appearing.
It has suffered slightly from Gall but nowhere near as much as the one in Blackburn, our previous house. The previous owner used to use a potato peeler and ‘peel’ the gall down to the interior holes as soon as she noticed it….. probably killing the larvae ?
Anyway, we’re still doing that, as the peeler is clipped to the tree and less seem to be appearing.
Hi Steve,
Thanks for sharing your experience and observations with us.
Good Luck & Happy Gardening
Duncan
They also seem to like gum tree leaves What is the best way to get rid of them pl
Hi Katie,
We have listed a few methods we use to control them in the article. You may also like to check out our citrus gall wasp experiment to see how effective the kaolin clay has been.
Good Luck & Happy Gardening
Duncan
Last year my lemon tree grew too much, had a very large crop of fruit but also an increase in the citrus gall wasp eggs.
So I am going to prune in late Spring/early Summer this year, then fertilise. It will be interesting to see what happens.
Hi Merilyn,
Sounds like a good plan. Please keep us all updated on your progress.
Happy Gardening!
I particularly am interested in lemon varieties which are gall wasp resistant, as we lost our last lemon tree to gall wasp infestation and “remedial pruning”.
Hi Graham,
most of the lemon varieties are susceptible to gall wasp. Avoid Meyer lemon though, it seems most susceptible out the the common options.
Good Luck & Happy Gardening!
Duncan
I have a lemon tree in my back yard that is very very very old, large, unruly-branches crossing all over each other, horribly infested with gall wasps, and sick looking – all the leaves are yellow and curling upwards… plus the top of the tree is covered by some invasive vine that drops dozens of these cluster/root type things. I think it probably hasn’t been pruned for >15 years. ALSO, some of the lemons have green spots.
Anyways, I think it is in need of a major prune, plus, the
Is there any contraindication to pruning? i.e. if the tree has a major nutrient deficiency, do i need to first correct the nutrient deficiency?? I don’t want to accidentally murder the lemon tree as i live in a rental.
I would like to follow your recommendation to fertilize from december-february, so I’m wondering when the best time you think would be for me to do a major prune?
Hi Amy,
Sounds like the tree is doing well, despite all the set backs. Without seeing the tree it is difficult for me to give specific advice. Generally you don;t need to correct nutrient deficiencies first. In fact pruning the tree can help correct these as there is less plant tissue to use limited nutrients.
There’s no perfect time to prune citrus trees in Melbourne as there is always flowers or fruit on the tree. However I would normally aim for early spring, as soon as all the current crop has been removed (difficult with lemons as they often have several crops at once). Be aware, that a hard prune will result in masses of water shoots. So you will need to conduct follow up prunes over the coming months to prevent your initial prune doing more harm than good.
Good Luck & Happy Gardening!
Duncan
what kind of pest that strips off the bark of my mandarin tree at night?
Hi Ken, rats are usually the culprit when bark has been removed. Hopefully they haven’t ring barked the tree and killed it.
Good Luck and Happy Gardening!
for an idea maybe a bunch of fresh growth branches hanging in the middle of the tree after spraying the tree with the clay spray, as a place for them to lay there lay.
Then dispose of after 12 day when the weather warms in spring.
Branches with swollen bit could be used, not with the swollen bit (cut up and put into bucket of water, something like an empty pot on top to keep them under the water). leave for several days, maybe a week and you can see dead ones on the surface.
I have treated my tree, but I will ask a neighbor for some of his branches and try this idea out.
A tip look all over branches in spring before it warms and I notice random little holes, (attack the wasp has its door open but has not left yet. Not just the swollen bits).
if you cut open you will see the little shit!.
I have confidor concentrate soon to arrive and I will use a little brush on any little hole I see.
This year is all out attack to low the population cycle on my tree in Melbourne.
cutting the swollen bits open has not seem to stop that remains.
Good luck
Hi Jason,
I like you thoughts on the decoy branches inside the canopy. That’s a great idea. Thanks for sharing.
Happy gardening!
Hi
Hope your experiment is going well.
I just pruned off all the Gal wasp lumps on my eureka lemon tree, leaving now half the tree only.
Will white oil help around July?
I’m in Melbourne.
Regards
Andrew
Hi Andrew,
White oil will only help where it can come in direct contact with the insect. In this case the gall wasp larvae are protect within the gall so the white oil will be useless against it. As discussed in the article, I don;t advocate for pruning the galls out either.
Happy Gardening
Duncan
What do you think of potato peeling the galls?
My experience is that I can only manage one smallish tree and that it prompts a new flush of growth. 😡
My other observation is that my wheeney grapefruit is “immune” but my marsh is affected like the lemon.
Hi Ivan,
you’ll see in the comments that this has been mentioned many times over. Your observations are correct, it promotes new growth, which is susceptible to gall wasp. It also only treats the symptoms rather than prevents infestation in the first place. I prefer kaolin clay because it prevents infestation.
Thanks for sharing your observation of the different grapefruit, very handy to know!
Happy Gardening!
Duncan
Hi, thank you for providing an easy to read, informative website.
I’m not a seasoned gardener by any means, but I’ve found that a simple application of, believe it not, Blu-tac seems to have prevented my Gall wasp problem.
Some time ago, I read that the wasp enters the plant via the cut surface of freshly pruned branches.
My lateral thinking proposed that covering this area could prevent access. It seems to have worked.
On a large scale, ie. an orchard, this would be improbable, but for backyard hacks like me, it may come in handy.
More experimenting to determine its effectiveness would be required, but hey, it’s worth a try.
Cheers.
Hi Peter,
Thanks for the great feedback and sharing your observations. In my experience the gall wasp ‘stings’ the new growth and lays eggs under the stem surface. Most galls seem to form on what was new growth in early summer. Therefore, I’m not sure how effective the blue tac method actually is. I suspect in your case it may be coincidental. It would be worth trying it on one half of your tree and leaving the other half bare. Then see if there are any differences in twelve months time.
Great work!
Duncan
I have had a few galls on my finger lime, but insignificant compared to the Tahitian lime. The Kaffir lime and the Meyer lemon are less affected than the Tahitian lime. I’m in Burwood Vic.
Hi Irene,
Thanks for sharing your interesting observations. I’m surprised that the Meyer lemon is less affected than the Tahitian lime as in my experience, the Meyer lemon is most susceptible to Citrus Gall Wasp.
Happy Gardening
Duncan
Am I right in saying that you can still feed the lemon tree in Spring, just not with Nitrogen.
Also would wrapping a bit of duct tape around the gall trap them ? I imagine it’d be removed as the tree grows
You can indeed feed a tree in spring. In fact we found through our experiment that it is best to feed them if you want fruit. Yes, it may increase the gall wasp infestation. Avoiding the fertilizer may reduce the galls, but it will also reduce the fruit.
Trapping the wasps from emerging may reduce the numbers in summer, but it won’t stop the tree being infested from wasps originating on other trees. Kaolin is best for preventing infestation in the first place.
Happy Gardening!
Thank you for your article and I thought I’d let you know what’s happened in our back yard yesterday. My husband was pruning the Tahitian lime tree and noticed black flying insects fly out from the top, one of which flew straight at him and stung him on his ear – he now has a very red and swollen ear, but no pain or itching. We’ve now noticed those swollen bits on a few branches that are obviously caused by gall wasps. But reading articles and looking at the life cycle pictures about the gall wasp, it seems that there shouldn’t be any flying around at this time of the year – early April? We are in outer Melbourne and are reluctant to even go near the tree now!
Hi Karen,
The Citrus Gall Wasp doesn’t sting humans – just citrus trees! Sounds like it might be a different type of wasp that’s living in the foliage.
Happy Gardening
Duncan
I am a novice citrus, lemon and lime, grower in Perth and have gall wasp issues. Pruning is not really an option as plants are young and would lose significant branches. Would like to try alternative options, thanks for the blog.
Hi Brad,
I’m glad you found the post useful.
Happy gardening
Duncan