Longtailed mealybug - biological control

A complex of seven species of encyrtid wasps, all accidentally introduced, have been found attacking longtailed mealybugs in New Zealand. These include three which have been widely used for the biological control of longtailed mealybugs in other parts of the world, Tetracnemoidea peregrina, Tetracnemoidea sydneyensis, and Anagyrus fusciventris. In various combinations, these parasitoids have been shown important for control of longtailed mealybugs in Australia (its area of origin), California, Bermuda, and Israel. A. fusciventris was first reported in Auckland in 1992 and further distribution of this wasp may assist biological control of longtailed mealybug. An introduced aphelinid wasp, Coccophagus gurneyi, three pteromalids, Ophelosia spp., and several predators also contribute to control. The most common predatory species are a ladybird, Cryptolaemus montrouzieri, a lacewing, Cryptoscenea australiensis, a midge, Diadiplosis koebelei, and a native hover fly, Melanostoma fasciatum. In overseas studies, outbreaks of longtailed mealybugs have been linked to destruction of natural enemies by insecticides. The production of honeydew by mealybugs also 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 longtailed 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 coolstorage or the use of an apple washer) to meet the nil tolerance prior to export. Natural enemies provide the principal control of longtailed 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.

Longtailed mealybug was first reported in New Zealand in 1890. 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 C. montrouzieri. All the other natural enemies of longtailed 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.