While the citrus gall wasp's natural host is the Australian finger lime (Citrus australasica), it can affect all types of citrus differently, including lemons, oranges and grapefruit. Understanding as much as possible about citrus gall wasps and other citrus pests can help protect your trees.
How to identify citrus gall wasps
Citrus gall wasps in your lemon tree are more complicated to spot than most garden pests because they are only 3mm tall. The easiest way to identify you have a citrus gall wasp infestation is by the appearance of galls, abnormal growths or swellings on various parts of the tree.
What do gall wasps do to citrus trees?
Adult citrus gall wasps lay eggs on the stems and bark of citrus trees during the warmer months. When the eggs hatch, the larvae release chemicals that induce the tree to form galls. Found on young stems and branches, Galls are swollen woody growths that vary in size.
As the larvae develop within the galls, they feed on the plant tissues, causing damage that can affect the tree's overall health. Infestations by citrus gall wasps can lead to a reduction in fruit quality. Galls formed on young branches can interfere with the transport of nutrients and water, affecting fruit development and potentially reducing yields.
Once the adult gall wasp reaches maturity, it will exit the gall. One of the most noticeable signs is small exit holes in the gall where the adult wasps have chewed their way out.
Why do gall wasps love citrus?
Gall wasps are attracted to citrus trees because they provide a suitable environment for their reproductive cycle and the development of their larvae. Citrus trees also have succulent, nutrient-rich tissues in their stems and branches for the larvae to feed on. Not to mention, citrus trees often grow in regions with climates favourable to the life cycle of the citrus wasp.
How to remove gall-infected stems
The best time to remove galls from your citrus is before spring. If there are only a few galls here and there, they can be pruned off and burned. Alternatively, try shaving one side of the gall with a sharp blade or vegetable peeler and cut only the bulging side. This is where the infestation lies. This exposes the larvae to air, drying them out and killing what's inside.
Whatever you do, do not discard pruned galls in your compost or green waste bin; this will only cause the wasps to spread. Instead, you can burn them or place them in a plastic bag in the sun for a few weeks.
How to prevent citrus gall wasp
A few preventive measures can assist in keeping citrus gall wasps at bay.
- Regularly inspect citrus trees for signs of galls.
- Avoid applying heavy fertiliser in winter or spring, which will promote new growth.
- Be careful not to over-prune your citrus tree in winter, as this encourages lots of new growth, perfect for citrus gall wasps.
- The best time to prune your citrus tree is from April to June.
Natural remedies for citrus gall wasps
As well as timing your pruning and fertilising, you can introduce natural enemies such as parasitic wasps, which parasitise gall wasp larvae. Additionally, Neem oil has insecticidal properties and can be used as a spray. But at the end of the day, the best thing you can do for your citrus tree is to provide proper nutrition, water, and care. Healthy trees are better equipped to handle insect infestations.
If citrus gall wasps become a severe problem for your trees, you can look into a chemical control method. That said, it's essential to remember chemical control methods may also eradicate beneficial "pests. Consult a local pest control expert for advice on safe and effective pesticides.