Leafroller larval and adult phenology at two Canterbury, New Zealand, organic apple orchards

Abstract

Leafroller larval and adult phenology were studied at two Canterbury, New Zealand, organic apple (Malus domestica Borkh.) orchards over three seasons. Larvae were sampled fortnightly from foliage and then reared to adult for unequivocal species-identification, or emergence of parasitoids. A total of 3304 larvae were found, comprising Planotortrix octo, Epiphyas postvittana, Ctenopseustis herana, and the most abundant larval parasitoid, Dolichogenidea tasmanica. There was an almost complete lack of C. herana larvae from 'Royal Gala' in 1993/94 and 1994/95, in contrast with its occurrence on nearby 'Red Delicious' in both seasons (9 and 11%, respectively of the total larvae at this site, cultivar, and year). Two larval generations per growing season were evident, with synchrony between the three leafrollers. The over-wintering larval generation of late instar P. octo in October/November was followed by an absence of larvae in late November. Early instar larvae then peaked in late December, with a second generation of this stage evident in March and April. Eggs were evident in December and from late February-April. Peak catches of males in pheromone traps were generally well synchronised with troughs in larval abundance.