BACILLUS-THURINGIENSIS SSP TENEBRIONIS SPRAYS AFFECT HATCHING OF COLORADO POTATO BEETLE (COLEOPTERA, CHRYSOMELIDAE) EGGS AND SUBSEQUENT LARVAL DISPERSAL

Laboratory and held experiments were conducted to evaluate the effect of Bacillus thuringiensis subsp. tenebrionis (Novodor Insecticide, Nov o Nordisk, Danbury, CT) sprays on hatching of Colorado potato beetle, Leptinotarsa decemlineata (Say), eggs and subsequent dispersal of larv ae. In laboratory treatments, nearly all egg masses hatch after treatm ents of 0, 0.2, 1.0, 5.0, and 10.0% (vol:vol) Novodor. Although all la rvae from egg masses treated with only water dispersed within 4 d of h atch, larval dispersal and subsequent survival was <50% in the 0.04% ( vol:vol) Novodor treatment, 4% in the 1 and 5% (vol:vol) Novodor treat ments, and 0% in the highest Novodor treatment. In the field, freshly deposited egg masses on eggplant were marked; spray applications of No vodor at rates of 0, 1.17, 2.34, 4.68, and 7.02 liters/ha were applied ; and the marked egg masses were monitored over the following 6 d for hatching and dispersal of larvae. Percentage egg masses hatching and d ispersal of larvae from the egg mass (survival) declined as the rate o f Novodor increased. Plots treated with the high rate (7.02 liters/ha) of Novodor had only 5% dispersal of larvae from treated eggs. These d ata show that B. thuringiensis subsp. tenebrionis applications on Colo rado potato beetle egg masses can be of benefit to growers by killing larvae as they emerge from the egg, thus reducing dispersal of larvae from the egg mass. Implications of this pesticide activity for pest ma nagement strategies are discussed.