Life History of the Butternut Curculio, Conotrachelus Juglandis (Coleoptera: Curculionidae), in Michigan

Abstract

Field studies were carried out in a mixed hybrid walnut plantation in Augusta, Michigan, in 1975-76 on the life history of Conotrachelus juglandis Lec. [see also next abstract]. There was one generation a year. Adults lived for at least one year, and females oviposited from mid-spring to late summer, resulting in considerable overlap of the life stages. Eggs were laid in niches chewed in young shoots. The egg, larval and pupal stages lasted 6-12 days, 4-6 weeks and 15-20 days, respectively. There were 5 larval instars, and larvae fed on pith within stems and caused girdling at the base of new shoots. Pupation occurred 7-10 days after larvae had entered the soil. The mean period between larvae entering the soil and adult emergence, which occurred from the second or third week in July to mid-September, was about 27 plus or minus 3 days. Newly emerged adults flew to host trees and fed at night or during the early morning on the soft tissues of shoot tips, leaf rachis and leaflets. Adults overwintered in cells in the soil beneath the tree canopy.