7 Most Common Citrus Pests & Diseases

Lemon tree gall wasps are a common pest that target soft, new shoots on lemon and other citrus trees. The adult wasps lay their eggs just under the bark, and as the larvae hatch, they trigger the tree to form unsightly woody galls around them. These lumps can stunt growth and weaken your tree over time.

The larvae develop inside the galls and eventually pupate. Come spring, adult wasps emerge through tiny holes and go on to infest more trees — especially those with fresh new growth.

You’ll start to notice galls forming from late autumn. While it might be tempting to prune them all out in winter, heavy pruning can encourage a fresh flush of soft new shoots right when adult wasps are emerging — and that’s exactly what they’re looking for.

Instead, the best method is to carefully slice open the galls with a sharp knife or even a potato peeler to expose the larvae inside. This disrupts their life cycle and stops the next generation.

Always dispose of the gall material by wrapping it in plastic and putting it in the rubbish bin — not your compost, where they could still hatch and spread.

This disease tends to show up around the graft union — the natural weak spot where the rootstock and plant were joined. If this area is damaged or sitting too close to moist soil, it can become vulnerable to fungal infections.

The best fix? Apply a fungicidal poultice to protect and treat the affected area. And as always, keep the graft above soil level and avoid overwatering to help prevent future flare-ups.

This tiny pest is a common culprit behind distorted, curly leaves and those tell-tale silver squiggles on lemon, orange and other citrus trees. Active from late December through to April, the citrus leafminer is actually a small, night-flying moth. It lays its eggs on the undersides of soft new leaves, where the larvae hatch and burrow just beneath the surface, tunnelling their way through the leaf.

While you can’t reverse the damage already done, applying a horticultural or eco oil every 2–3 weeks during the active period will help control new infestations and protect fresh growth.

This pesky pest is becoming more common across Australia — now reaching as far south as Victoria, though it’s still most active in the warmer, more humid regions of NSW and Queensland. Female fruit flies lay their eggs inside ripening fruit, causing it to rot from the inside out.

To help protect your citrus, it’s important to collect and dispose of all fruit, including any that have fallen to the ground. Yellow sticky traps and liquid lure traps are highly effective — they attract the flies and stop them before they can do damage.