Treating Citrus Gall Wasp in Melbourne: An alternative approach to “Prune in June” 69

What is the Citrus Gall Wasp?

Citrus Gall Wasp Melbourne

Citrus Gall Wasps (Bruchophagus fellis) emerging from a citrus gall.

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 create 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.

Observation’s I’ve made when growing citrus

At Leaf, Root & Fruit we implement and maintain many edible foodscapes across Melbourne. Citrus trees are a popular fruit tree and many of our 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 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. We’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 they 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 fertilized heavily in spring, summer and autumn. Heavy fertilizing 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.

Citrus Pests and Diseases Melbourne

Citrus Galls caused by the Citrus Gall Wasp are traditionally pruned out in June or July to prevent reinfection in spring.

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 fertilizing 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. 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. So 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 our citrus variety guide for more ideas.

The general timing of events related to growing citrus in Melbourne. Please note, some of these events may vary slightly for different citrus varieties. This is especially the case for lemons which may have multiple crops per year.

The Leaf, Root & Fruit Citrus Gall Wasp Experiment

To test these theories, we are going to set up a trial to see which management practice is most beneficial for growing citrus.

We will purchase ten small lemon trees that are relatively identical in size, shape and stage of growth. The trees will be paired up and allocated to five different treatments:

  • Citrus Galls pruned out in June every year, fertilized monthly Sep to May.
  • Citrus Galls pruned out in June every year, fertilized monthly in Dec and Jan only.
  • Citrus Galls not pruned out, fertilized monthly Sep to May.
  • Citrus Galls not pruned out, fertilized monthly in Dec and Jan only
  • Citrus Galls not pruned out, fertilized monthly Sep to May, treated with calcined kaolin clay (Surround®).

This experiment will run for several years. We will be regularly looking at the overall tree health as well as productivity. Further details on the experiment, as well as periodic updates will be found on our Citrus Gall Wasp Experiment Page. We will also keep you updated on the results as they develop and share them on our Facebook Page and our newsletter.

Want to know more about growing citrus in Melbourne? Check out our handy 5 part growing guide.

Have you made any similar observations to ours? 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.

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69 thoughts on “Treating Citrus Gall Wasp in Melbourne: An alternative approach to “Prune in June”

    • Leaf, Root & Fruit Post author

      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!

  • Nancy

    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.

    • Leaf, Root & Fruit Post author

      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.

    • Maryann

      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

      • Leaf, Root & Fruit Post author

        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!


  • Barbara Austin

    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.

    • Leaf, Root & Fruit Post author

      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


    • Leaf, Root & Fruit Post author

      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!

  • Ruth Williams

    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!

    • Leaf, Root & Fruit Post author

      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!

  • Olwyn Smiley

    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!

    • Leaf, Root & Fruit Post author

      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!


    • Laura

      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.

  • Chris Newman

    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.

    • Leaf, Root & Fruit Post author

      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!

      • RoseMarie

        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.

  • christopher torr

    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

    • Leaf, Root & Fruit Post author

      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!

  • Gabriella Hont

    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.

  • Ruthie

    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.

    • Leaf, Root & Fruit Post author

      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!


  • Barry Mackay

    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.

    • Leaf, Root & Fruit Post author

      Thanks for sharing your experience Barry. Please keep us all updated on your outcomes.

      Good Luck and Happy Gardening!


    • Barry Mackay

      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.

  • Hel

    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’.

    • Chris Newman

      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?

      • Leaf, Root & Fruit Post author

        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


        • Chris Newman

          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.

  • Dave Brown

    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.

    • Leaf, Root & Fruit Post author

      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!


  • Nicole

    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

    • Leaf, Root & Fruit Post author

      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.


  • Sardar

    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.

    • Leaf, Root & Fruit Post author

      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.

  • David Salter

    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.

    • Leaf, Root & Fruit Post author

      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!


      • David Salter

        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.

  • Anna S

    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?

    • Leaf, Root & Fruit Post author

      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.


    • Leaf, Root & Fruit Post author

      Thanks for the great feedback Iris. Glad you’ve found our site useful.

      Good Luck and Happy Gardening!


  • Deb Taylor

    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!!

  • Roz Averis

    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.

    • Leaf, Root & Fruit Post author

      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!


  • Graeme

    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?

    • Leaf, Root & Fruit Post author

      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!


  • Helen Bayes

    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?

    • Leaf, Root & Fruit Post author

      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!


      • Helen

        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.

  • Jon Buttery

    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

    • Leaf, Root & Fruit Post author

      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


  • Kenny

    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.


    • Leaf, Root & Fruit Post author

      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.


  • Ann-Maree

    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?

    • Leaf, Root & Fruit Post author

      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!


    • Leaf, Root & Fruit Post author

      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!


  • Anja

    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?

    • Leaf, Root & Fruit Post author

      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!


  • David Salter

    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.

    • Leaf, Root & Fruit Post author

      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!