Citrophilus mealybug - biological control

The citrophilus mealybug originates from Australia and now occurs in many parts of the world. In the absence of disruptive pesticides, natural enemies provide effective biological control in its area of origin and in a number of other locations. In California, the combined activities of two wasp species are particularly effective, the encyrtid Tetracnemoidea brevicornis and the aphelinid Coccophagus gurneyi. In Italy, another encyrtid wasp Tetracnemoidea peregrina is the most common parasitoid of citrophilus mealybug. All three of these wasps occur in New Zealand, particularly the first two, and they are assisted by a fourth, the encyrtid Anagyrus fusciventris. Two predatory wasps, Ophelosia spp., and several predators also contribute to control, the most common being a lacewing, Cryptoscenea australiensis, and a midge, Diadiplosis koebelei. The production of honeydew by mealybugs attracts ants which may interfere with the performance of natural enemies, particularly parasitoids. Control of the ants often improves the effectiveness of biological control.

This complex of natural enemies gives (or at least has the potential to provide) very effective biological control of citrophilus mealybug on New Zealand pipfruit in the absence of broad spectrum pesticides. However, mealybugs are quarantine pests in some overseas markets and further control may be required (such as a postharvest apple washer) to meet the nil tolerance prior to export. Natural enemies provide the principal control of citrophilus mealybug in organic production and they make an increasing contribution to integrated fruit production as more selective insecticides, such as Applaud®, are introduced. Cultural control can also assist.

Citrophilus mealybug was first reported in New Zealand in 1878. Several attempts have been made to introduce natural enemies from overseas in classical biological control programmes. However, the only successes have been C. gurneyi and the ladybird, Cryptolaemus montrouzieri. All the other natural enemies of citrophilus mealybug in New Zealand have arrived by accident. C. montrouzieri can be mass produced and has been trialled for mealybug control by inundative release overseas.