Seasonal crawling activity of adult root-feeding insect pests (Coleoptera: Curculionidae; Scolytidae) of red clover

Pitfall traps located between red clover, Trifolium pratense L., stands and adjacent pasture and woods were used to monitor seasonal and directional crawling activity by adults of four species of root-feeding insect pests of red clover: Hylastinus obscurus (Marsham), Calomycterus setarius Roelofs, Sitona flavescens Marsham, and Sitona hispidulus (F.). Trapping was conducted at a site in Monongalia County, West Virginia, from May to November 1990, March to December 1991, and April to June 1992. Peak crawling activity by H. obscurus occurred in June. Peak C. setarius activity was from June to September. Peak S. flavescens activity occurred from April to May and from September to November. S. hispidulus had three periods of peak activity: in the spring (April-May), summer (mid-June-mid-July), and fall (September-mid-November). Few directional trends in movement were apparent for H. obscurus and S. flavescens, indicating that their movement by crawling is limited to short distances within or between red clover stands. Most C. setarius were caught in traps located between the red clover and adjacent woods. Movement into the red clover was primarily from the direction of the woods. During its period of summer activity, S. hispidulus movement from the red clover was directed toward adjacent woods. During spring and fall, greater numbers of S. hispidulus adults moved toward the red clover from adjacent woods than from the red clover toward the woods, and movement from the red clover was toward adjacent pasture