Bean leaf beetle, Cerotoma trifurcata (Forster) (Coleoptera: Chrysomelidae), is an economic pest of soybean in Ontario. Field cage studies were conducted in 2010-2011 to determine voltinism in southern Ontario and the effect of C. trifurcata feeding during soybean reproductive stages on soybean yield and quality. Thermal requirements for C. trifurcata development were determined in a laboratory study. Results of field and laboratory studies support the occurrence of one generation of C. trifurcata in southern Ontario. Pod-feeding increased with both number of beetles and soybean reproductive stage. An increase in defoliation and a reduction in seed quality were observed with increasing number of beetles. Monitoring programs for late-season pod-feeding should begin when degree days approach 500 (base 9.31°C). Economic thresholds for C. trifurcata during soybean reproductive stages range from 0.27 to 2.00 beetles per plant or 8 to 60 beetles per m of row. / Ontario Ministry of Agriculture and Food – University of Guelph Sustainable Production (Plants) Program and Grain Farmers of Ontario through the Farm Innovation Program.

The bean leaf beetle (BLB), Cerotoma trifurcata (Forster) (Coleoptera: Chrysomelidae), is a pest of commercially produced legumes in eastern Virginia. Field cage and manual-defoliation studies were conducted in Virginia to determine an economic impact of BLB. In the manual-defoliation study, snap bean plants had significant yield loss when > 25% of leaf area was removed. In the field cage experiments, I was unable to establish beetle densities per plant to impact yield. Host plant selection by BLB was done in laboratory and field studies with snap bean, lima bean, and soybeans. Laboratory studies showed that BLB preferred snap bean and lima bean over soybean. Field studies did not showed no preference. A survey was conducted on the Eastern Shore of Virginia determine the epicenter of BPMV. Soybean leaves and beetles were collected and assessed for BPMV by ELISA or TBIA. Beetles at the ESAREC were BPMV-positive upon emergence from overwintering sites, but the virus load was low when tested by ELISA. This suggests acquisition of virus from a source other than infected cultivated legumes. To find the potential inoculum sources of BPMV in eastern Virginia, leguminous weeds and perennial weeds were tested for BPMV. Four weed species gave BPMV-positive tissue blots including: Oxalis stricta, Rumex acetosella, Trifolium pretense, and Trifolium repens. Insecticidal seed treatment of thiamethoxam on soybean seeds was evaluated to test the efficacy. Leaf area eaten and beetle mortality was measured. The thiamethoxam seed treatment protected soybean seedlings from beetle feeding through the V2 stage of growth. / Master of Science in Life Sciences