Alfalfa Consumption by Adult Clover Leaf Weevil (Coleoptera: Curculionidae) and Development of Injury Equivalents for Stubble Defoliators

摘要

Experiments were conducted from 1990 through 1992 to determine consumption rates and feeding duration of adult clover leaf weevils, Hypera punctata (F.), to characterize the injury potential of this species during alfalfa regrowth. Adults were fed for 29 d in 1990 and 18 d in both 1991 and 1992. The mean cumulative consumption per adult was 27.2 ± 1.6 cm2 and 92.7 ± 3.5 mg dry weight in 1991 and 24.6 ± 0.9 cm2 and 87.5 ± 2.9 mg dry weight in 1992. The mean cumulative consumption pattern was curvilinear for both dry weight and leaf area consumption. Most consumption was within 11 d of adult eclosion. The peak consumption rate occurred ~5 d after adult emergence. Because the highest consumption rates and the greatest percentage of defoliation were within the first 11 d of emergence, adult clover leaf weevils potentially can delay regrowth of alfalfa stubble when adult emergence coincides with the 1st harvest. Further, because adult consumption patterns between clover leaf weevils and alfalfa weevils are similar, alfalfa stubble defoliation thresholds developed for alfalfa weevils and cutworms also can be used for clover leaf weevils. Injury equivalents (injury by 1 species in terms of another species) are determined for adult clover leaf weevils, larval variegated cutworm, Peridroma saucia (Hubner), and larval and adult alfalfa weevils, Hypera postica (Gyllenhal).