Comparative feeding by three chrysomelid (Coleoptera : Chrysomelidae) species on eight soybean genotypes

The feeding rates on soybean, Glycine mau (L.) Merr., by three beetle speci es, Cerotoma trifurcata (Forster), Diabrotica balteata LeConte, and Colaspi s louisianae Blake, were compared in bioassays in the laboratory. Eight soy bean genotypes, including two resistant standards (PI171451 and PI229358), a resistant line (D89-9121), four resistant commercial cultivars (Lamar, Ly on, Crockett, and Shore), and a susceptible standard (Centennial) were plan ted on the research farm at St. Gabriel, LA. Beetles were collected from th e field throughout central and south Louisiana, separated by gender, and pl aced 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 cons umed more Centennial foliage than foliage from PI229358, PI171451, Lyon, an d 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 significa ntly among beetle species, but not among soybean genotypes. Diabrotica balt eata suffered the highest mortality and C. trifurcata the lowest. The resul ts suggest cultivars resistant to C. trifurcata and D. balteata should also be effective against C, louisianae.