Biology of Trichogramma minutum Riley Collected from Apples in Southern Ontario

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Abstract
A strain of Trichogramma minutum Riley collected from codling moth (CM) Cydia pomonella (L.) in southern Ontario was studied to assess its potential as a biological control agent for that species. The threshold temperature and degree-days (°D) far development were found ta be 128°D 10.2 Feeding the wasps diluted honey increased fecundity 6-fold and longevity 9-fald aver unfed wasps. Unmated females lived longer than the mated females but their fecundities were not significantly different. Longevity and fecundity at 25°C were 25.5 days and 236.8 eggs per female. Longevity varied inversely, while daily fecundity varied directly with temperatures between 15 and 35°C. At 35°C, however, fecundity decreased considerably, signifying an adverse effect of high temperature. T. minutum preferred eggs of CM and ariental fruit moth, Grapholitha molesta (Busck), to those of Mediterranean flour moth (MFM), Anagasta kuehniella (Zeller), and oblique-banded leaf-roller, Choristoneura rosaceana Harris, even though they had been reared on MFM eggs for about 22 generations. Parasitism of CM eggs depended on the age of the eggs and density of the parasitoid. Residues af the insecticides permethrin and phosmet on apple leaves significantly lowered rates of parasitization by T. minutum on eggs of CM far mare than 16 days. Residues af azinphosmethyl and phosalone, however, were virtually nontoxic 16 days after application.

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