Ecology of the eastern larch beetle, Dendroctonus simplex LeConte (Coleoptera: Scolytidae), in Newfoundland

Langor, David William (1985) Ecology of the eastern larch beetle, Dendroctonus simplex LeConte (Coleoptera: Scolytidae), in Newfoundland. Masters thesis, Memorial University of Newfoundland.

	[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (10MB)
	[English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (12MB)

Abstract

The ecology of the eastern larch beetle, Dendroctonus simplex LeConte, was studied in Newfoundland. Overwintered beetles emerged in May. One generation and two broods were produced in both 1983 and 1984. Females initiated attacks and males arrived up to two days later. One to four pairs of beetles used each entrance hole but each pair constructed a different gallery. -- Egg galleries were vertical, slightly sinuous and averaged 41 cm in length. Females laid zero to four eggs per niche averaging 1.4. The average number of eggs per gallery and per cm of gallery was 39 and 1.0, respectively. Mean brood density was 49 individuals per 100 cm². -- About 90% of all parents reemerged and a small proportion of them attacked a second group of trees and produced a second brood. Galleries in second brood trees averaged 26 cm in length and 27 eggs per gallery. Mean brood density averaged 23 individuals per 100 cm². Following brood production 61% of parents reemerged and likely died. -- Development from egg to adult averaged 60 to 70 days for first and second broods, respectively. -- During egg gallery construction and oviposition D. simplex flight muscles degenerated. Flight muscles were completely regenerated in only 17% of 96 reemerged beetles in 1984. No reemerged beetles were observed to fly. -- Emergence, host attack and reemergence occurred between 10:30 and 17:00 hours and at temperatures of 4 ﾟC or higher. Peaks of attack, which reflects flight peaks, occurred at temperatures of 10 ﾟC or higher. -- Only adults overwintered. Freezing temperatures caused high mortality among immature stages of the second brood. -- Thirty-four percent of new brood adults emerged in the fall and reentered galleries at the base of trees for hibernation. -- The fourth larval instar had the highest mortality, at 29.2%, and pupae the lowest, at 7.6%. Total mortality was 79% and 82% for first and second broods, respectively. Pathogens caused the largest proportion of mortality among eggs, second instar larvae and pupae, resinosis among first instar larvae and parasitoids among third and fourth instar larvae. Overwintering mortality was 7.8%. -- Fifty-two species of insects, spiders, mites and nematodes were associated with D. simplex in 1983.

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