The life history, habits and some aspects of the natural control of Choristoneura Fumiferana (Clemens) (Lepidoptera: Tortricidae) in Newfoundland

Crummey, Hubert Ralph (1976) The life history, habits and some aspects of the natural control of Choristoneura Fumiferana (Clemens) (Lepidoptera: Tortricidae) in Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

The eastern spruce budworm, Choristoneura fumiferana (Clem.), is a univoltine species in Newfoundland and has six larval instars. Head capsule width differences occurred between the sexes only in instars V and VI. -- Needle mining occurred on all three host tree species, and was of the longest duration on black spruce. -- Adults were present from late July to mid-August. The first adults to emerge were invariably males; females emerged several days later. The sex ratio was 1:1. -- Females preferred white spruce and balsam fir to black spruce in laboratory experiments when all three hosts were offered simultaneously to them for oviposition. There was an average of 16 eggs per egg mass (21 eggs per mass in the field); 54% of the masses had two rows of eggs, 20% had two rows plus a partial third, and 26% had three rows. Hatching success of the eggs was 99%. -- Based on 18-inch branch samples, there were 3 times as many larvae on white spruce as on black spruce and 4 times as many on balsam fir as on black spruce. Larval development was the fastest on white spruce and the slowest on black spruce. -- Weather seemed to have little direct effect on budworm survival. The major predators were birds; ants and other insects may also have destroyed some. Thirteen primary parasitoid species, including one pupal parasitoid, were reared during the study. Mortality due to parasitoids was less than 19% on average for the two years, but was higher in 1974 than in 1973. The two most important species were Glypta fumiferanae (Vier.) and Apanteles fumiferanae Vier., which accounted for about 18% of the total parasitism during the study, Glypta being more numerous. -- Two species of fungi, Entomophthora sphaerosperma Fres. and E. egressa MacLeod and Tyrrell, were observed to cause mortality. The combined mortality of larvae and pupae due to these fungi for both years, was 16%. -- Defoliation of the new growth on the sample trees in both 1973 and 1974 was approximately 99%, 87% and 70% for balsam fir, white spruce and black spruce, respectively.

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