The life history of Codling Moth, Cydia pomonella (L) (Lepidoptera: Tortricidae), in the Australian Capital Territory.

Abstract

The life habits of codling moth in the Australian Capital Territory are described, and the ecological characteristics of the species and its environment are defined. In the Capital Territory, codling moth produces a complete first generation, a partial second generation, and some third generation individuals each summer. On an average, females lay between 40 and 50 eggs in all generations, but fecundity varies much between individuals. The observed distribution pattern of eggs and larval injuries to fruit suggest that oviposition occurs predominantly on trees at, or near, sources of females. In uniformly infested, homogeneous orchards, egg and damage distribution are almost random between trees. No significant departure from randomness was detected either between fruits, or between locations within trees. Fruits are often penetrated by more than one larva, either simultaneously or in succession, and competition occurs. Its forms and effects were examined. Fruits penetrated by several larvae tended to produce more mature larvae than fruits penetrated once, but the chances of survival fell as the numbers of entries per fruit increased. Fully fed larvae move from the fruit to an appropriate place on, or very close to, the host tree, where they spin a cocoon and eventually pupate. Under natural conditions in the Capital Territory, most mature larvae perish before establishing a cocoon. The rate of establishment was shown to be directly dependent upon the abundance and accessibility of suitable cocooning sites. The injuriousness of codling moth is always extremely high in the Capital Territory because of the generally favourable weather conditions. Particular effects of climate and weather on codling moth activity are discussed. Optimum environmental conditions for codling moth are defined. Conditions in the Capital Territory were found to be nearly optimum in most respects. Codling moth abundance cannot be explained by single ecological factors. Comprehensive studies of local populations are required to understand the numerical determination of the pest.