A SURVEY OF MEALYBUGS AND THEIR NATURAL ENEMIES IN HORTICULTURAL CROPS IN NORTH-ISLAND, NEW-ZEALAND, WITH IMPLICATIONS FOR BIOLOGICAL-CONTROL

More than 1300 mealybugs and their natural enemies were collected from six crops (apples, pears, nashi, citrus, persimmon and grapes) at 91 sites. Pseudococcus longispinus and P. calceolariae were the commonest species in all crops, except in pipfruit in Hawkes Bay, inhabited almost exclusively by P. affinis. These three species accounted for more than 99% of all mealybugs collected. Mealybugs were attacked by 14 species of natural enemy, only two of which had been deliberately introduced to New Zealand. Six species of Encyrtidae were I-eared. Anagyrus fusciventris was recorded from New Zealand for the first time. Parectromoides varipes was newly identified as a primary parasitoid of mealybugs, and males of this species and Gyranusoidea advena, previously unknown, were found. Both species, together with Tetracnemoidea sydneyensis, T. peregrina and T. brevicornis, and Coccophagus gurneyi (Aphelimidae) and two species of Ophelosia (Pteromalidae) were widespread throughout the surveyed regions. Common predators included Cryptolaemus montrouzieri (Col: Coccinellidae), Cryptoscenea australiensis (Neuroptera: Coniopterygidae) and Diadiplosis koebelei (Dipt: Cecidornyiidae). Hyperparasitoids were extremely rare. Five species of ants were recorded tending mealybugs, but none is known to be disruptive to mealybug natural enemies. The implications of these data for biological control of mealybug pests in horticultural crops is discussed, and it is concluded that Pseudaphycus maculipennis (Hym: Encyrtidae) should be introduced against P. affinis. No other importations are recommended. The activity of existing species should be encouraged in future integrated pest management (IPM) programmes, by, for example, distributing A. fusciventris around the country, and commercializing the mass I-earing and release of C. montrouzieri.