Field Observations On Flight And Oviposition Of Codling Moth (Carpocapsa pomonella (L.)) and mortality of eggs and first-instar larvae in an integrated control orchard

Abstract

Codling moth (Carpocapsa pomonella (L.)) usually had one generation a year in Nelson, although a small second generation (1–2%) occurred occasionally. The flight period extended from the end of October until early April, with slight variations according to season and locality. Peak emergence was usually during December and January, and appeared to be delayed by cold weather during October to December.

Oviposition was contemporaneous with flight. Most eggs were laid on fruits or on leaves near fruits. Eggs were laid at random with regard to individual fruits, although this distribution was disrupted at high population densities. The frequency distribution of eggs on fruit clusters appeared to be mildly contagious, there being fewer clusters with single eggs and more with two or more or no eggs than would be expected if eggs were laid at random. Multiple oviposition was rare, and the nonrandom distribution of eggs could be partly explained by there being more eggs per cluster in the upper half of the trees than in the lower half. The distribution of eggs was not affected by aspect. Trees with the most fruit tended to have the most eggs.

Natural mortality of eggs was low (4.7–6.9%) in the integrated control orchard and was due to inviability and disappearance from the tree. There was a 25.8% mortality of eggs in an orchard which had never been sprayed with broad-spectrum insecticides, and parasitism by Trichogramma sp. (14%) was the principal factor. Only one egg out of 342 observed in both orchards was preyed upon.

Natural mortality of young larvae on unsprayed trees was 10%. No predation was observed, and little was suspected. Application of ryania with a hand sprayer gave a greater mortality of fìrst-instar larvae before damage to fruit (74%) than application with a turbo-mist sprayer (42–48%), probably due to giving a more uniform cover of insecticide throughout the trees. Larvae entering fruit sprayed with ryania suffered 68-82% mortality compared with 11.1% on unsprayed trees.

Suggestions are made for improving control of codling moth in an integrated control programme.