If your citrus trees are suffering, it's tempting to blame Medfly — but WA gardeners are increasingly dealing with two major citrus pests, and mixing them up leads to the wrong treatment (and wasted money).
Here's how to confidently identify whether you're dealing with Mediterranean fruit fly or citrus gall wasp, and what to do about each.
Citrus Gall Wasp (Bruchophagus fellis)
What It Looks Like
Citrus gall wasp causes distinctive woody lumps or galls on the stems and branches of citrus trees — most commonly on lemons, limes, and grapefruit. The galls are caused by wasp larvae developing inside the branch tissue.
Damage Pattern
- Swollen, knobbly growths on young branches and shoots
- Weakened branches that die back or produce less fruit
- No damage to the fruit flesh itself
When It Strikes
Adults emerge and lay eggs in spring (August–October in WA). By the time you see galls, the eggs have already hatched and the larvae are inside.
What to Do
- Prune out galls before August (before adults emerge) and dispose of prunings in a sealed bin bag — not the compost
- Use a dedicated trap — our Go Natural Citrus Gall Wasp & Med Fruit Fly Trap Kit (Twin Pack) targets both gall wasp and Medfly in one kit, with a safety cage design
- Do not use insecticide sprays — the larvae are inside the wood and not reachable
Mediterranean Fruit Fly (Ceratitis capitata)
What It Looks Like
Medfly is a small mottled fly (4–5mm) that you'll rarely see directly. Its damage shows up as stung or sunken spots on fruit skin, followed by internal rotting and maggots in the flesh.
Damage Pattern
- Soft, discoloured patches on ripening fruit skin
- Premature fruit drop
- Maggots (white larvae) visible inside cut fruit
- Affects the fruit, not the branches
When It Strikes
Year-round in WA, but peak activity from October to April when fruit is ripening and temperatures are warm.
What to Do
- Place Mediterranean fruit fly–specific traps in your garden from September
- Apply protein bait sprays weekly during peak season
- Remove and bin fallen fruit promptly
Side-by-Side Comparison
| Citrus Gall Wasp | Mediterranean Fruit Fly | |
|---|---|---|
| Damage location | Branches and stems | Fruit flesh |
| Visual sign | Woody lumps/galls | Soft spots, maggots in fruit |
| Peak season | Spring (Aug–Oct) | Spring–Autumn (Oct–Apr) |
| Treatment | Pruning, dedicated traps | Lure traps, protein bait |
| Insecticide effective? | No | Limited – use bait stations |
Can You Have Both at Once?
Yes — and many WA citrus growers do. Gall wasp has been spreading rapidly through Perth suburbs in recent years, while Medfly is a permanent fixture. If your lemon tree has galls and your fruit has maggots, you're dealing with both and need separate management strategies for each.
Our Go Natural Citrus Gall Wasp & Med Fruit Fly Trap Kit (Twin Pack) is perfect if you're battling both pests — it handles gall wasp and Medfly in a single solution. For Medfly alone, the Fruit Fly Trap Kit for WA Mediterranean Fruit Fly covers a full season. For broader garden pest management, browse our Pest Control range.