Use of Beauveria Bassiana for Suppression of Colorado Potato Beetle Populations in New York State (Coleoptera: Chrysomelidae)

In a 3-yr study, field plots of Katahdin potatoes in Tully, N.Y., were treated with Beauveria bassiana (Balsamo) Vuillemin at rates of 5 × 1012 and 5 × 1013 colony-forming units/ha for control of Colorado potato beetle (Leptinotarsa decemlineata (Say)). B. bassiana treatments were compared with a control of water plus surfactant and with insecticide treatments of oxamyl (184 g active ingredient [AI]/ha) in 1983, or fen valerate (18.4 g [AI]/ha) in 1983, or fen valerate (18.4 g [AI/ha) plus piperonyl butoxide (PBO) (73.6 g [AI]/ha) in 1984 and 1985. In 1983, B. bassiana and control treatments were not significantly different regarding larval populations or tuber yield, but few adults emerged from B. bassiana-treated plots. Field-collected third- and fourth-instar larvae developed B. bassiana mycoses (98% of the test population for the high rate of B. bassiana and 64% for the low rate) when held at high humidity conditions (RH \u3e 90%) for 11 d. Because the B. bassiana formulation rapidly lost \u3e90% of the spore viability before applications were initiated, no significant results were observed in 1984. The 1985 B. bassiana formulation maintained spore viability well and produced significant reductions in third- and fourth-instar larval populations (65.8% for high and 39.5% for low B. bassiana treatments). For high and low treatments in 1985, respectively, 28.3% and 20.0% of field-collected third- and fourth-instar larvae that were held at high humidity conditions developed B. bassiana mycoses. Adult emergence studies using field cages indicated no reduction in 1985 adult populations for the low B. bassiana treatment, but a 71.6% reduction in the high B. bassiana plots. Total 1985 marketable tuber yields for fenvalerate + PBO, high B. bassiana, low B. bassiana, and control treatments were, respectively, 28.2, 13.6, 8.2, 3.2 t/ha, and were significantly different for all treatments