Distribution and Abundance of a Stem Weevil, Cylindrocopturus adspersus (Coleoptera: Curculionidae), in Cultivated Sunflower in the Northern Plains 1

Abstract

Larvae of a stem weevil, Cylindrocopturus adspersus (LeConte), overwintered in sunflower stalks in North Dakota, South Dakota, and Minnesota in 1979 and 1980. Population levels averaged 2.0 and 1.6 larvae per stalk in 1979 and 1980, respectively. The highest number of overwintering larvae per stalk occurred in North Dakota. About half of the stalks from each sampled field were infested with larvae. There was no correlation between stalk diameter and number of larvae per stalk. Overwintering sites were in the upper root crown and in the base of the plant stalk, with half the larvae between soil level and 4 cm above soil level. Overwintering sites averaged 5.9 and 4.6 cm above the soil level in 1979 and 1980, respectively.