Do you know the signs of citrus gall wasp?

Imagine a teeny-tiny insect with the power to destroy your beloved citrus tree. Meet the Citrus Gall Wasp.

March 25, 2024

Citrus gall wasp is an Australian native insect that likes nothing better than taking up residence in your citrus trees. Originally drawn to finger limes, this dastardly creature has now taken a fancy to a wide array of citrus trees, making itself at home in our gardens. They create ‘galls’ on citrus trees that are like roadblocks for nutrients, stunting new growth and messing with fruit production; this can lead to smaller fruits, fewer yields, and in the worst cases, the tree can die.

  • The citrus gall wasp produces a single generation each year, spending most of its growth and development inside galls in branches.

  • The adult wasp lays its eggs inside the stem of the tree.

  • After they hatch, a woody gall forms around the larvae usually on young green branches. The growing insect lives off the sap of the tree.

  • Although an infestation of gall wasp may not kill a citrus tree, the damage it causes is unsightly and can weaken the tree.

  • Repeated attacks can lead to leaf drop, spindly growth and make the tree unproductive.

The galls start to be visible in February and are easy to see by June. The best time to check and remove the galls is from April to June, before the adult wasps emerge.

  • Inspect the new young growth on all citrus trees and look for galls forming on young, green twigs.

  • Galls on older branches can indicate older infestations (previous year or earlier).

  • If there are small holes on the gall, then adults have already emerged.

Here are some tips to protect your citrus trees:

  • Inspect your citrus trees from April to June, looking for the early signs of galls on young, green branches. Pruning these galls before the end of June can interrupt the wasp's lifecycle.

  • Galls removed after June may contain mature larvae. Treat these galls by placing them in a sealed black plastic bag and putting the bag in full sun for at least four weeks. The heat from this process of solarising will kill the adult.

  • Pruning the galls is essential for controlling this pest. Prune off new galls before the end of June. The larvae inside the gall will not survive without food and the gall wasp will not mature. Pruned material should be disposed of in green waste or general rubbish.

  • Galls removed after June may have more mature larvae that will mature and emerge as adult wasps.

  • Avoid heavy fertilizing in winter and spring, as the new growth attracts the adult wasp.

  • Encourage your neighbours to inspect their citrus trees regularly. Since the wasps can't fly far, controlling them locally can be effective.

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