Gall Wasp

August 07, 2018

Gall Wasp


Citrus Gall Wasp Control

Citrus Gall Wasp (Bruchophagus fellis) is native to Queensland and northern NSW, with the Australian Finger Lime as its natural host. Unfortunately citrus trees, particularly lemons and grapefruits are now part of its diet. This pest has spread south (and west) in recent years where it can survive the cold and has no natural predators. Drat!



Living up to its name, Citrus Gall Wasps trigger a reaction in the host causing it to produce large lumps or ‘galls’. Heavily galled trees lose vigour, which can result in reduced fruit size and yield. Sometimes the gall causes new growth at right angles.



12 Month Life Cycle

Understanding the Citrus Gall Wasp life-cycle is very helpful for control. Adult gall wasps begin to emerge from their galls in Spring (from late August – October depending on area & season) to coincide with Spring growth, and can continue until mid-December. Most wasps emerge around the same time – within 20 days or so. After emerging, females take 5 – 7 days to mate. Then they begin laying eggs just under the bark, preferring soft, lush Spring growth. Larvae hatch in 2 – 4 weeks and feed within the stem for 9 – 10 months. The resulting woody gall becomes visible from December and expands until the cycle repeats in Spring.

The wasps themselves are tiny (2-3mm long) so they can’t fly far. Upon exiting they leave tell-tale exit holes. Galls with such holes do not require removal.


Control Methods

Currently there is no chemical control registered for home gardener use to control Citrus Gall Wasp. Effective control therefore relies on strategic timing of both pruning and fertilising, augmented by traps. Correct disposal of gall prunings is essential to stop the spread .


Pruning and Fertilising Timing

Traditionally the recommendation for gall wasp control is pruning in August before the wasps emerge. This is suitable in the short term, if your infestation is small and on the end of branches, or if you have only noticed the galls in Winter. On the down side, August pruning can trigger the tree to put on a flush of Spring growth – which will then be targeted by any Gall Wasps present, perpetuating the cycle. Expected Spring growth can be protected to some degree by traps.

For longer term control and tree heath, gardeners with significant infestations should aim to reduce susceptible Spring growth flush by:

  • pruning galls from trees in Summer as they become visible (from about December). General maintenance pruning should be done at this time also; and
  • fertilising in Summer and Autumn. Heavy ferrtilising in Winter and Spring will only encourage “tasty” Spring growth.

 To maintain vigour, only remove 30% or less of your citrus tree at any one time.



Regular monitoring of galling throughout the year will assist in pruning and avoid nasty surprises. Cutting galls open in late Winter to see keep an eye on wasp development may be helpful... after a few years you will get the idea.


Insect Traps

Used on their own, these traps are unlikely to be effective. When their use is in conjunction with pruning; timed to wasp emergence (August – October); for protection of young trees, or some unavoidable Spring growth, then 2 – 4 traps per tree will contribute to control. The attractant used is not specific to Gall Wasp so removal in October, after wasp emergence is a good idea – you don’t want to trap beneficial insects or small birds as well.






Slicing open the Gall

Some gardeners have had success by slicing open the gall and exposing enclosed larvae to the elem
ents – thereby killing it. This is worth a try, particularly if you have dwarf citrus or the gall is located on vital part of the tree’s branchwork. The trick here is again in the timing and depth of cut. Don’t wait until galls are big and surrounding tissue is brittle and there is no need to cut too deeply as the stem needs to continue supporting it’s own weight.


Stop the Spread!

Gall Wasps cannot fly far and are mainly transported by wind or sadly, by prunings. It is vital to dispose of any removed galls in a manner that will not allow the wasp to emerge. Methods suggested include burning (I’ve heard of gardeners roasting them in the oven!), burying (1m), cutting up into tiny pieces (mulching), or soaking in water for 2 weeks. They definantly cannot be disposed of via council green waste or garbage collection services – this is known to spread the problem.


Help is on the Way!

NSW Department of Agriculture has conducted some trials using Kaolin clay (Surround®). This product is registered for sunburn and unfortunately cannot be used for Gall Wasp control yet. Results however look promising for the future.

Here at Fruit Salad Trees, we stock a wide range of fruit trees, which all boast different fruit on the same tree. Each fruit variety retains its own flavour, appearance and ripening time. We graft citrus, stonefruit and multi-apple trees. 

Our fast fruiting trees can be grown in the ground, or in pots on your balcony.

Shop our wide range of trees now and check out our current specials here!

Useful Links

    Leave a comment

    Comments will be approved before showing up.

    Also in News & Tips

    Apples for all climates
    Apples for all climates

    October 12, 2018

    It is believed that eating an apple every day reduces the risk of having a stroke and lowers bad cholesterol. Apples are high in fibre and Vitamin C and low in sodium (salt) and calories. There are a few different varieties of apples available on our Fruit Salad Trees, that not only look fantastic when they are growing, but they taste better than anything you will purchase in a store. Best of all you know you have grown them yourself!

    Continue Reading

    Thinning the first fruit on your Fruit Salad Tree
    Thinning the first fruit on your Fruit Salad Tree

    October 03, 2018

    Your Fruit Salad Tree is beginning to bear its first fruit - it's a momentous occasion! You'll be tempted to sit back and let your tree continue to develop its array of different fruit, however, it's best to let the tree use its energy to grow sturdy framework and the first fruit can pull down the young branches.

    Continue Reading

    Balancing your Fruit Salad Tree
    Balancing your Fruit Salad Tree

    October 02, 2018

    Establish a well-balanced Fruit Salad Tree by pruning back the more vigorous growing grafts which are Nectarines, Peaches, Yellow Plums, Lemons, Pomelo and Grapefruit. You can do this anytime, especially during the fruiting season.

    Continue Reading