Lumpy bits – Citrus Gall Wasp

My citrus are under attack, I have found the dreaded lumps on my Eureka Lemon, Meyer Lemon, Orange and Lime.  Unlike many of Australia’s pests citrus gall wasp is actually a native annoyance.  Having lived for years in our native limes it is now more likely to make its home in backyard lemons and limes along Australia’s East Coast.  It has so far ignored my finger lime in favour of its imported cousins.  Citrus gall wasp is a tiny wasp which lays it eggs in the new growth of citrus trees and as the larvae grow bumps appear on the branches of the trees.

When the larvae emerge in early Spring they leave small tell tale holes in the bumps.  Citrus gall wasp has the ability to severely limit the growth of trees, so my understanding is that it is best to do something about it.  With my lemon, which is in the ground, and has been for a couple of years, I pruned off the affected branches and placed them in the garbage.  With my dwarf potted citrus – the Meyer lemon, Tahitian Lime and the Navel Orange to prune off the affected branches would be to decimate the tree completely.  With these I have tried a different tact.  I have taken a slice out of each bump which although it is damaging the tree it is also killing the larvae.  As you can see below – the larvae have fallen out of the little holes in each bump.  Whether this will have gotten all the larvae in each lump remains to be seen but I felt it was more likely to save the tree than radical pruning would.

Whether this will be a completely successful method of getting rid of citrus gall wasp remains to be seen.  At the very least it should limit the number of larvae hatching.  I will isolate the affected plants in late winter (you should act against the wasp by late August as they hatch soon after) to try and stop it spreading to my other potted citrus.  I do hope I get rid of it as I love my citrus and they aren’t cheap to replace.  Its always the tinniest creatures that seem to do the most damage, as my black aphid eaten garlic chives will attest.

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26 Responses to Lumpy bits – Citrus Gall Wasp

  1. Diana says:

    looking forward to hear the results.

  2. Mark Willis says:

    Hmm, the “surgery” route, as opposed to “medication”. I trust you had a really sharp scalpel Dr. Liz! A drastic approach, but probably effective. Hopefully the trees will produce scar tissue to seal their wounds. Is there any chemical remedy available?

  3. Nina says:

    You are scaring me, Liz! As soon as I get the chance, I’ll be checking my one and only lemon tree for gall wasp. I’ve been here for over 15 years and it was a mature tree before I moved in. I’d be devastated if I lost it. The only other citrus I have is a young, yet to fruit, patio lime that’s in a pot. Some aphids have found it appealing but apart from that, it looks okay (apart from NO fruit!).

    • Liz says:

      Hi Nina, I don’t mean to be the bearer of bad tidings. Even if you do find some lumps I wouldn’t worry too much – I don’t think they will kill the tree – at least not quickly. Some may be old galls – if they have little holes in them it means the galls have hatched out, and others may be easily pruned off without the tree noticing too much.

  4. leduesorelle says:

    “Black aphid eaten garlic chives”?! Yet another thing to worry about… sigh.

  5. Jo says:

    There’s always something waiting to attack, it’s a wonder we end up with anything to harvest for ourselves after all the pests have taken their turn.

  6. This annoying little beast saw the end of my last dwarf lemon tree. After I took the severe pruning route it just never recovered. I now have a gorgeous lemon/lime which is looking the picture of health. I’ll be devastated if it gets attacked. I saw galls in a friends lemon/lime last week, she hadn’t realised what it was, but it was severely effected, perhaps I’ll suggest your method.

  7. Annie says:

    We have the same problem. Our beautiful huge lime tree is covered with gall wasp lumps. Although we’ve pruned it like mad, we haven’t been able to remove all the lumps. We might try your approach – hopefully it works.
    We also have a very small lemon tree that’s just started to get lumps. Do you think we should cut it right back?

    • Liz says:

      My understanding is that pruning off the affected branches should get rid of them but you do run the risk of killing the tree. If you are going to prune or cut the galls you have to do it by the end of August. My thinking is that if you can get rid of it by pruning a third or less of the tree then perhaps try pruning but I would wait until late August, prune and then give it a good feed as that shoudl co-incide with when it would be starting to grow again after winter. If you would have to prune off more than a third of its branches then perhaps try the other method. I should point out though that so far I’m not sure if it works. I’m also not sure what effect ignoring it would have. More galls, but how much damage they do I couldn’t really tell you.

  8. We have two big old lemon trees with the lumps. They’ve had them for ages and I confess I haven’t even tried to get rid of them. The trees still produce well – it doesn’t seem to have affected them. I wonder if I should be worried?

    • Liz says:

      If it aint broke don’t fix it…I wouldn’t worry too much – my understanding is that once the lumps are there they stay there even if the actual wasps are long gone. My understanding is that they are a bigger problem for small trees as although they don’t kill the trees they can weaken them and make them unlikely to bear fruit (or bear much fruit). If you are still getting lots of fruit I personnally wouldn’t worry too much. If your production slows a lot maybe do something about it then, or if you want to give the trees a prune then use that as an opportunity to get rid of some.

  9. Louise says:

    Bummer. My experience is this. These gall wasps are pretty nasty in Melbourne but only a small problem in Sydney ( touch the wood of citrus!) I get the occassional sting and after the Melbourne expereince surveille pretty seriously. I had a very badly affected, very old but productive lemon in Melbourne and only prunned where the wasps had obviously not emerged ( ie where the galls had no holes in them). I fed and fed and waterered and watered, mullched and mulched and rid myself over time of most of the problem. I think you are in more danger of weakening your tree by being too zealous on the prunning, than weakening the tree from a few gall waps but that is my humble opinion and I am a bit of a pest tolerator…….. obviously there is a balance somewhere here, I know not what it is.

    Good luck, I wonder if this is yet an another ‘disadvantage’ of La Nina! Just when you think you have all the luck in the world with rain!

    • Liz says:

      I suspect you are right about over zealous pruning. I am becoming more and more pest tolerant, I find that with some notable exceptions nature does sort things out for itself. I think your approach of strengthening the trees as much as possible is probably the right one.

  10. Jen says:

    Ohh nooo… I planted a dwarf lime tree and it was beautiful at first with plenty fruit. This last spring we had several larvaes eating the leaves of the tree, in which at first I didn’t know what they were, but later came to find out they turned into these beautiful butterflies, but ever since then, the branches all got really bumpy and cracky looking like, sort of like the picture you posted. The tree has no longer beared any fruit. :(

    • Liz says:

      Hi Jen, It sounds like you have citrus gall wasp, but I don’t think it was anything to do with the butterflies as gall wasps are different again. I pruned a lemon tree with them quite a bit last year and it is coming back pretty well. How much of your lime would you have to chop off to prune them out? My understanding is that you need to do it pretty much now – have a look if the lumps have little holes in them – if so its too late for pruning to have an effect on wasp populations as the wasps have hatched. It might still be worth cutting out any wood that looks really damaged in the hope of promoting healthy growth.

  11. Paul Tyrrell says:

    I have a 2.5 year old Eureka Lemon tree, it is infested, there are only two branches with new shoots the rest have blackened tips and no growth. The lumps escaped my focus, as I am not familiar with Lemons and didn’t realise the sinister problem lurking underneath. I did notice in the first year limited new leaves forming. Yesterday I went to an excellent old orchard come nursery Morrison brothers near Doncaster and the owner Graham suggested a hybrid approach of slicing the lump and spraying with pyrethrum. He also said that spraying with white oil in Autumn may also be effective. I have probably left it too late, but I am going to try to save this little tree.

    • Liz says:

      I tried the slicing approach – no need to spray as well as the lavae just fell out when exposed to the air. Not sure if you would be too late trying now as they may have hatched. Most of the literature suggests that you can tell if they’ve hatched by examining the lumps and if you find holes they already hatched out. I wouldn’t bother slicing any with holes as the horse has bolted but any others it may work for. The branches where I did that are putting on new growth so it does seem to be working OK. How those branches will be long term I don’t know. On my trees with less infestation i pruned out the affected branches which worked well. i will give the white oil a try in Autumn.

  12. Ann Maree says:

    Hi Liz, it’s now been over 12 months since the gallectomy – how are things progressing? Strangley enough, I did the same thing with my tress last weekend before I read your info.

    • Liz says:

      I think the jury is still out. It didn’t get rid of all of the wasps as they a few emerged on the other side of the branches from where I cut. But I do think there were significant less galls this year. The tree isn’t as vigorous as some of my other citrus either but that might be a variety thing. Having said that I don’t think it particularly liked having have its bark cut out and it did take a long time to put out much regrowth at all. The lemon that I hard pruned to remove all the galls regrew much better but it hard pruning didn’t get rid of the wasp. The trees I didn’t prune at all seem healthiest despite a few galls so my approach this year is going to be to prune out any really swollen branches but otherwise leave them and hope the trees are healthy enough to cope.

  13. Rebecca says:

    From what I’ve heard pruning is the only real method to get a citrus back to healthy growth after gall wasp. The problem is that the lumps actually block a great deal of sap flow between the leaves and the roots, hence the tree can’t function properly. This results in less or no fruit and less new growth.

    • Liz says:

      Yeah I reckon you’re right. My problem is that for some plants that means pretty much decimating the plants but I think I will just have to bite the bullet and do it this year.

  14. Sean says:

    I’ve noticed a plethora of these knotty lumps on my kafir lime- my elderly neighbour actually brought them to my attention by saying, “your lime tree has cancer.” (!)

    Anyway, for what it’s worth as I’m no expert, I’ve since been told that in a cruel twist of evolution, these little nuisances are also incredibly poor flyers. Meaning any that hatch pretty much just fall to the base of the tree & just climb back up it to re-continue the cycle.

    For the record, I haven’t done anything about the lumps (part of me suspects I’ve left it too late), but mainly because the most troublesome lump is at the very base of the plant- meaning I’d need to lop the whole thing down to remove them. Or do the slicing method you mentioned above.

    My understanding is that the tree continues to grow regardless, if that offers any condolence.

    • Liz says:

      Thanks Sean. I am finding that different plants seem to cope with them differently. They don’t seem to have affected the productivity of some of plants too much but for others they have. Glad they haven’t affected your Kaffir Lime too badly – are you still getting lots of fruit on it?

  15. Pingback: Citrus Gall Wasp – Pruning | Suburban Tomato

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