Effect of Root Size and Soil Moisture on the Number of Clover Root Borers Present in Red Clover Roots

Abstract

During 2 consecutive years, similar field experiments were condoled in New York to study the effects of red clover ( Trifolium pratense L.) root size and percentage available soil moisture on numbers of the clover root borer, Hylastinus obscurus (Marsh.) (Scolytidae: Coleoptera). In 1956, as soil moisture decreased, borer numbers increased; as root size increased, borer numbers increased. A multiple regression analysis indicated that either root size or soil moisture could account for most of the variation in borer numbers, because the two independent variables were closely correlated to each other: as soil moisture decreased, root size. Increased. In 1957, it was found that root size alone was responsible for the majority of the variation in borer numbers. On the basis of these data and differences in the number of areas sampled, the distance between sampling areas, Uniformity, and ranges of soil moisture in 1956 as compared with 1957, the conclusion was reached that root size has a more direct influence than soil moisture on borer numbers. Soil moisture is believed to indirectly affect borer numbers owing to its influence on root size.