Phyllobius oblongus and Sciaphillus asperatus Associated with Sugar Maple Reproduction in Northern Michigan 123

Abstract

The bionomics of 2 weevils, Phyllobius oblongus (L.) and Sciaphillus asperatus Bonsdorff (Coleoptera: Curculionidae) were studied in Michigan during 1972–74. P. oblongus adults were present from late May to about July 20. Adult abundance peaked during the 3rd week of June. Adults fed on 22 plant species, but primarily defoliated sugar and mountain maple, American elm, yellow birch, and black cherry. They laid eggs a few cm into the soil. The mean hatch was 24.2 days. The larvae fed on young rootlets of sugar maple and other host trees. Five larval instars occurred from late June until late fall. The insect overwintered as a mature larva and pupation occurred in early spring. The mean duration of the pupal stage was 17.7 days. Most twig scarring, resulting in terminal die-back and forking on small sugar maple trees, was caused by S. asperatus adults. Sugar maple was the primary host of S. asperatus . Dense adult populations were found in all study areas from late April until late September. Surveys of 6600 sugar maple terminal buds showed an average of 0.28 terminal buds per 100 stems per year damaged by weevil-like bud feeding. No conclusive causal agent was determined, but S. asperatus was the most probable suspect.