Integrated control of apple pests in New Zealand

A technique is described whereby 5th‐instar larvae of the codling moth (Laspeyresia pomonella) which have finished feeding can be tagged externally with cobalt‐58 and released on apple trees, where they seek cocooning sites. Two μCi ⁵⁸Co per insect did not significantly affect larval survival in the field, or subsequent pupation, emergence, mating, and oviposition in the laboratory. Tagging was more efficient than whole‐tree scraping for the location of cocoons, and was non‐destructive of both the insects and their cocooning sites.

Relocation and observation of the tagged larvae in their cocoons permitted accurate estimation of mortality from when they left the fruit (= release) until adult emergence in the following spring. Natural mortality of larvae seeking cocooning sites was attributed mainly to insect predators, and varied significantly between trees and blocks, averaging 57% over 6 years. Avian predation by the silvereye (Zosterops lateralis) was the greatest hazard to cocooned larvae; this, too, varied significantly between blocks, and averaged 53% over the same period. Both mortalities appeared to be density‐related.