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Citrus gall wasps (Bruchophagus fellis) are small wasps that are native to some parts of Australia. If left unchecked, they can cause significant damage to a variety of different citrus plants. Wasp larvae develop within a gall (abnormal growth) on a plant’s branches, and it’s this form that harms the plant. We’re sharing advice on how to identify citrus gall wasps and how to protect your plants.
Safety tip: Always wear the appropriate safety equipment (safety glasses, gloves, and a mask, for example) and always follow the instructions for the product or equipment. Always store products out of the reach of children and pets.
Adult citrus gall wasps are dark brown or black in colour. They emerge from the galls (which look like bulbous growths on the branches of citrus trees, pinpricked with tiny holes) in the spring. Once they emerge, they have about one week to mate and will proceed to lay approximately 100 small, white, oval-shaped eggs under the bark. These eggs turn yellow and then orange prior to hatching.
Once the eggs hatch into larvae (approximately two to three weeks), they burrow deep into the stems or branches of citrus plants, creating the gall. The larvae will become full-sized wasps in about a week. It’s a swift lifecycle, and one that can quickly get out of control if it’s not nipped in the bud.
Tip: Because the adult wasps are small (3mm in size) and difficult to spot, keep an eye out for the woody cylindrical galls. The symptoms of citrus gall wasps are more apparent than the actual wasp!
The wasp larvae inside the galls affect the flow of water and sap through the affected branches. This, in turn, negatively affects the health of the plant. The galls themselves weaken the trees, reducing fruit size and yield, and causing branch dieback.
Citrus gall wasps also spread easily, so it’s important to keep them under control – for your own plants, your neighbour’s plants and to help protect Australia’s valuable citrus industry.
There are three ways to keep these wasps in check.
1. Be vigilant. Regularly inspect citrus plants for symptoms of citrus gall wasps, especially from the end of summer to early winter. Remove galls immediately by pruning (see Step #2), and – where possible – isolate infested plants so they don’t infect other plants. Keep the contaminated plants isolated until you are certain the wasps are under control.
Avoid heavy fertilisation of your citrus trees in winter or spring – excessive new growth is attractive to gall wasps. Also, stressed plants are more prone to insect attack. Keep plants well-fed and watered all year round.
2. Be hands-on. Prune any galls from the tree as soon as they become visible, up to the point where the gall is located. Double bag and dispose of the infested galls in the rubbish. Do not compost infected branches.
Alternatively, you can carefully peel or cut off the bark around the gall with a sharp knife or potato peeler to expose the larval forms, which will then die off. This is best done in mid to late winter.
Traps are also an effective way to reduce citrus gall wasp populations. The traps contain a pheromone to lure the wasps when they first emerge, trapping and preventing them from continuing their lifecycle.
3. Use pest control, such as an insect-killing spray. This can be tricky. Adult citrus gall wasps are small and difficult to see, and they are only visible for a short time; juvenile citrus gall wasps are protected by the woody gall they live in.
You can use the spray on emerging insects, but timing is crucial: There is only a small window in which to smother the emerging insects before they fly away. Sprays that have oils work best. Kaolin clay-based products have also been proven to be effective.
Check out our guide to common lawn pests - we’ll help you identify the pest so you know your treatment options.
Asbestos, lead-based paints and copper chromium arsenic (CCA) treated timber are health hazards you need to look out for when renovating older homes. These substances can easily be disturbed when renovating and exposure to them can cause a range of life-threatening diseases and conditions including cancer. For information on the dangers of asbestos, lead-based paint and CCA treated timber and tips for dealing with these materials contact your local council's Environmental Health Officer or visit our Health & Safety page.
When following our advice in our D.I.Y. videos, make sure you use all equipment, including PPE, safely by following the manufacturer’s instructions. Check that the equipment is suitable for the task and that PPE fits properly. If you are unsure, hire an expert to do the job or talk to a Bunnings Team Member.
