Ancistrocerus gazella (Hymenoptera: Vespoidea: Eumenidae): A potentially useful biological control agent for leafrollers Planotortrix octo, P. excessana, Ctenopseustis obliquana, C. herana , and

Abstract Ancistrocerus gazella (Panzer 1798) was found to prey almost exclusively on caterpillars of the lepidopterous family Tortricidae. This family includes New Zealand's most damaging pests of fruit crops—the leafroller moths Planotortrix octo, P. excessana, Ctenopseustis obliquana, C. herana , and Epiphyas postvittana . In Central Otago, A. gazella is limited primarily by an absence of nesting sites. When artificial trap nests consisting of small holes bored through blocks of straight‐grained wood taped together in bundles of 4–64 traps, and larger compound nests consisting of blocks of wood through which 64 evenly‐spaced holes were drilled, were placed at a height of 1.5 m in orchards, fields, and open places where A. gazella occurred, the trap nests were filled with P. octo, P. excessana, C. obliquana , and E. postvittana (> 90% of prey) and much lower numbers of other Tortricidae. A 64‐hole nest was set up in the wild where A. gazella was plentiful until all holes were filled, 18 days later, as indicated by plugs of mud across the nest entrances. At that stage, the nest was removed to an abandoned orchard in another locality. After the second generation A. gazella females emerged and mated, they filled a new nest placed beside the one in which they were raised with leafrollers from the fruit trees. Their old nest also was reused. It is suggested that A. gazella can be used to control all pest leafroller species in New Zealand berry crops in integrated management systems, with reduced use of insecticides and in conjunction with sex phermone mating disruption techniques.