The short version: Citrus gall wasp is a tiny native wasp whose larvae cause woody swellings, or galls, along citrus stems. No treatment turns an existing gall back into normal stem, so management is about removing or treating active galls before the adults emerge in spring. The best time to act differs between states: Victoria and Western Australia recommend pruning galls from late summer or autumn to the end of June, while peeling galls is a separate job done later in winter. Treat cut galls before you dispose of them, and never compost them untreated.
On this page:
- Identify the gall
- Why timing matters
- Choose the right action for the season
- Treat cut galls before disposal
- Citrus gall wasp across Australia's climate zones
- Frequently asked questions
If your lemon or grapefruit has developed knobbly, woody lumps along its stems, citrus gall wasp is a likely cause. The wasp itself is only about three millimetres long and rarely seen, so the galls are usually the first sign.
Happy Valley Seeds does not sell citrus trees, so this is advice only, but it is a common enough backyard problem to be worth getting right.
Identify the gall
Look for woody, lumpy swellings along twigs and young branches, which form as the larvae feed inside the stem. New galls become visible from about April and are obvious by June. Galls covered in tiny round exit holes are old galls the adults have already left. In newly infested branches the galls are small and hard to see, so from spring to early autumn also look for light green shoots growing out at right angles from the branches. Galls reduce the tree's vigour, fruit size and yield, and heavy galling can cause branch dieback, though it rarely kills an established tree.
The wasp, Bruchophagus fellis, is native to the coastal area around the Queensland and New South Wales border, where its natural host is the native finger lime. It has adapted to garden citrus such as lemons and grapefruit, and has spread through the eastern states, including Victoria and South Australia, and to suburban Perth.
Why timing matters
Citrus gall wasp has one generation a year. The adults emerge in spring and early summer, mate, and lay their eggs into soft new growth. For southern Australia, Agriculture Victoria puts emergence at mid October to mid December, with most adults about from late October to mid November. In Western Australia, DPIRD gives September to December, earlier in warmer climates.
The larvae then feed inside the stem for most of the year while the gall forms around them. Removing or treating active galls before the next emergence reduces the number of wasps from your tree. The wasps tend to stay close to where they emerged, often on the same tree, but they also spread to nearby citrus, so Agriculture Victoria encourages neighbours to monitor and manage their trees together.
Choose the right action for the season
- Prune out active galls early. Agriculture Victoria recommends pruning galls from April to June, because pruning later in winter pushes the flush of soft spring growth the wasps prefer to lay into. DPIRD in Western Australia recommends pruning new galls from February to the end of June, and avoiding heavy pruning in July and August. South Australian advice is to remove galls at least a month before spring emergence and avoid winter pruning.
- Peel galls you do not want to prune. Agriculture Victoria describes slicing the top off one side of an active gall with secateurs, a sharp knife or a potato peeler, which exposes the larvae and kills them without lasting damage to the tree. The best time is mid to late winter, later than the pruning window. Cut with the blade facing away from your body.
- Avoid forcing soft growth. Heavy pruning late in winter, and heavy fertilising in winter or spring, encourage the flush of fresh growth the wasps prefer. Agriculture Victoria also advises against pruning every year, because a yearly flush of new growth can keep the cycle going.
- Check your state's guide. Advice differs between states. New South Wales guidance, for example, allows galls to be cut in winter in new infestations, provided it is done well ahead of emergence.
No spray removes existing galls. Agriculture Victoria notes that petroleum spray oils and kaolin clay can deter adults from laying eggs, and that chemicals used against the wasp also affect the tiny parasitic wasps that attack its eggs and larvae. If you consider any product, check that it is registered for the use and follow the label.
Treat cut galls before disposal
Wasps can still emerge from galls in cut branches, so treat them before disposal and do not put untreated galls in compost.
- Bag them in the sun. Victoria and Western Australia both describe sealing cut galls in a well-sealed plastic bag and leaving it in the sun for about a month (at least four weeks in Western Australia).
- Check local rules for what happens next. Agriculture Victoria warns that putting gall off-cuts in household rubbish, green waste collections or garden bags spreads the pest. South Australian options include mulching, freezing for 24 hours, or sealing galls tightly in a bag for the general waste bin. In Western Australia, DPIRD says galls cut from February to June can go in green waste, while those cut from July to November need treating first.
Citrus gall wasp across Australia's climate zones
Where the wasp is established, and whose advice to follow, depends on your state or territory more than your climate. These zones are broad groupings, so if your garden sits between two, go by your local conditions.
- Tropical (far north Queensland, the Northern Territory Top End, the Kimberley in Western Australia): we found no records of citrus gall wasp in the Northern Territory. If you see woody galls on citrus in an area without the wasp, report them to your state or territory biosecurity agency.
- Subtropical (south-east Queensland, northern New South Wales): this includes the wasp's native range. We could not find a Queensland home-garden guide, so the New South Wales guidance is the closest reference. Check stems for new galls from autumn.
- Arid and semi-arid (inland New South Wales and Queensland, Mildura and north-west Victoria, the South Australian Riverland): follow the guide for your state, and keep in mind that emergence can start earlier in warmer areas.
- Temperate (Sydney and coastal New South Wales, the ACT, Melbourne and much of Victoria): established in New South Wales and Victoria. In Victoria, prune galls from April to June and peel from mid to late winter.
- Mediterranean (Perth and south-west Western Australia, Adelaide and southern South Australia): established in suburban Perth and in South Australia. In Perth, prune new galls from February to the end of June.
- Cool and alpine (Tasmania, alpine and highland Victoria and New South Wales): we found no records in Tasmania. In cooler parts of Victoria and New South Wales, follow that state's timing.
Frequently asked questions
What are the woody lumps on my lemon?
Most likely galls, where the stem has swollen around citrus gall wasp larvae feeding inside. Galls with many small round holes are old galls the adults have left.
When should I prune the galls?
It depends on your state. Victoria recommends April to June, Western Australia February to the end of June, and South Australia at least a month before spring emergence. In every case, act well before the adults emerge in spring.
Can I peel the galls instead of pruning?
Yes, on wood you want to keep. Agriculture Victoria describes slicing the top off one side of an active gall from mid to late winter.
Can I compost the prunings?
Not untreated. Seal cut galls in a plastic bag in the sun for at least four weeks, then follow your state's rules for disposal.
Will it kill my tree?
Usually not. It reduces vigour, fruit size and yield and can cause dieback, and young trees are set back the most.
Will a spray fix it?
No spray turns existing galls back into normal stem. Removing or treating active galls at the right time is the main approach, and any spray should be a registered product used as the label directs.
Check your citrus for new galls from autumn, deal with them in your state's recommended window, and treat the prunings before disposal, and citrus gall wasp should stay manageable.
Sources we checked
Written by the Happy Valley Seeds team. Last reviewed on 18 September 2026. We checked the main facts in this guide against these sources:
- Agriculture Victoria: Citrus gall wasp
- Department of Primary Industries and Regional Development, Western Australia: Citrus gall wasp control
- PIRSA, South Australia: Citrus gall wasp
- NSW Department of Primary Industries and Regional Development: Citrus gall wasp in Southern Australia
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