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Citrus leaf miner – silvery lines on leaves.

There is one pest that has been making an appearance in almost every garden, and that is the citrus leaf miner, Phyllocnistis citrella. They are a common pest that attack citrus trees from summer to autumn, especially when the weather isn’t consistent. But they can also prove to be a problem in the early months of spring when the new season’s growth starts to emerge. The adult is a tiny moth that is silver-white in colour with yellow markings and they have an approximate wingspan of 5mm. The adult moth lays their eggs onto the undersides on the new foliage, and once these eggs hatch that is when the symptoms and damage is most noticeable.

When the eggs have hatched the larvae begin to tunnel in between the fine layers of the leaf. This process usually takes the young caterpillar 5 days to do. Affected trees will show symptoms in the foliage and overall appearance. Silver aztec maze designs appear on the leaf surface and can cause the foliage to discolour overtime. Foliage can also be distorted and curled. Other symptoms can cause plants to wilt and in heavy infestations can cause affected trees to suffer from stress and remain unhealthy for long periods of time.

When the affected foliage starts to curl along the margins the larvae are fully grown. The larvae curl the sides of the leaf to create a ‘shield’ to protect itself as it goes through pupation. The pupation can take up to 3 weeks to complete and then the adult wasp emerges and the cycle repeats.

The best method of control is to prune off all affected growth then follow up by spraying an organic pesticide such as EcoPest Oil by Multicrop or Pest Oil by Yates. Don’t apply it on a hot sunny day.

Citrus leaf miner can be found on other plants so make sure to check over surrounding plants. Also you could avoid using a high nitrogen fertiliser in summer, as this promotes very soft new growth that makes them very attractive to these insects.

By Bonnie-Marie Hibbs

Images by Bonnie-Marie Hibbs

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