Comparative Feeding by Three Chrysomelid (Coleoptera: Chrysomelidae) Species on Eight Soybean Genotypes

The feeding rates on soybean, Glycine max (L.) Merr., by three beetle species, Cerotoma trifurcata (Forster), Diabrotica balteata LeConte, and Colaspis louisianae Blake, were compared in bioassays in the laboratory. Eight soybean genotypes, including two resistant standards (PI171451 and PI229358), a resistant line (D89-9121), four resistant commercial cultivars (Lamar, Lyon, Crockett, and Shore), and a susceptible standard (Centennial) were planted on the research farm at St. Gabriel, LA. Beetles were collected from the field throughout central and south Louisiana, separated by gender, and placed in Petri dishes with leaflets of known leaf area. Feeding, mortality, and oviposition were monitored daily for 5 d. Per capita daily consumption by C. louisianae and D. balteata averaged between 3.5 and 2.5 mg dry weight, and C. trifurcata consumed 7.6 mg dry weight. Beetles of all species consumed more Centennial foliage than foliage from PI229358, PI171451, Lyon, and Shore. Consumption of other soybean genotypes varied among beetle species. Number of eggs deposited by C. trifurcata and C. louisianae did not vary significantly among soybean genotypes. Diabrotica balteata females were not observed ovipositing on leaves of any cultivar. Mortality varied significantly among beetle species, but not among soybean genotypes. Diabrotica balteata suffered the highest mortality and C. trifurcata the lowest. The results suggest cultivars resistant to C. trifurcata and D. balteata should also be effective against C. louisianae.