Influence of soil moisture and weed density on clover root curculio sitona hispidulus larval stress to alfalfa medicago sativa

Godfrey L. D.; Yeargan K. V.

A greenhouse study was conducted to evaluate the effects and interactions of clover root curculio, Sitona hispidulus (Fabricius), larval feeding, soil moisture level and weed competition on alfalfa growth. Potted plants were subjected to three insect densities (0, 50 or 100 eggs/pot), three soil moisture levels (19, 27 or 35%) and two weed levels (present or absent). Clover root curculio larval establishment was inhibited (0.9% survival) by the saturated (35%) soil moisture conditions and averaged 7.0% within the 27 and 19% moisture treatments. Yield results indicated that the effects of clover root curculio larval feeding were negated by the wet soil conditions (27%). However, in the dry soil regime, alfalfa dry weight yield decreased with increasing insect densities from 1.28 g (0 eggs/pot) to 0.93 g (50 eggs/pot) to 0.71 g (100 eggs/pot). Weed presence reduced alfalfa dry weight yield by 66.1%. Significant effects and interactions were also observed with alfalfa percent moisture, alfalfa stem density and stem height.