Effects of pasture management factors on red clover root and stand characteristics and observations of seasonal crawling activity of root-feeding insect pests of red clover.

摘要

Red clover (Trifolium pratense L.) is a high quality forage; however, its use may be limited by root-feeding insects (Hylastinus obscurus (Marsham), Calomycterus setarius Roelofs, Sitona flavescens Marsham, and S. hispidulus (F.)) and root diseases. Little information is available concerning the impact of pasture management practices on such pests. This study was done from 1988 to 1992 to determine effects of management factors (soil fertility, harvest frequency, and harvest intensity) on red clover root and stand characteristics. Pitfall trapping was conducted during the study to monitor movement of root-feeding insects.;Two sets of experimental plots were established at a site near Morgantown, WV by sod seeding Kenstar red clover into natural pasture in April 1988 and April 1989. Each set had a 3 x 3 x 2 factorial randomized complete block design with four blocks. Soil fertility treatments were (1) low (no amendment), (2) medium (4500 kg/ha lime, 49.5 kg/ha P), and (3) high (4500 kg/ha lime, 274.5 kg/ha P). Harvest frequencies were (1) low, (2) medium, and (3) high, harvested 2, 4, and 6 times per season, respectively. Harvest intensities were (1) low and (2) high, cut to 13 and 8 cm, respectively. Clover roots were sampled at the end of the first and second harvest years and forage yield sampled at each harvest.;High harvest intensity reduced the number of H. obscurus per root by up to 58% and reduced the percentage of red clover roots infested with H. obscurus by up to 39% compared with low harvest intensity. Forage yield and legume yield were up to 38% and 12% greater, respectively, with high harvest intensity compared to low harvest intensity.;Hylastinus obscurus and C. setarius crawling activity occurred primarily during summer. High levels of activity of S. flavescens and S. hispidulus occurred in spring and fall. Sitona hispidulus also had a period of summer activity. Few directional trends in activity were apparent for H. obscurus or S. flavescens. Movement of C. setarius into clover was primarily from the direction of adjacent woods. Summer movement by S. hispidulus was toward adjacent woods: fall and spring movement was towards clover and adjacent pasture.;These results indicate that a complex of root-feeding insect pests may be active in areas of sod-seeded red clover. Pasture management techniques such as high harvest intensity may be useful in reducing the impact of such pests.