PLANT RESISTANCE Insecticidal Activity of Avidin Combined with Genetically Engineered and Traditional Host Plant Resistance Against Colorado Potato Beetle (Coleoptera: Chrysomelidae) Larvae

Colorado potato beetle,Leptinotarsa decemlineata (Say), is a destructive pest of potato, Solanum tuberosum (L.), in North America. It is renowned for adapting to insecticides. With the arsenal of effective insecticides decreasing, it is important to consider alternative forms of control. Biotin is an essential coenzyme for insect growth and development. Avidin is a protein found in chicken egg that sequesters biotin and has shown insecticidal properties against a range of insect. We assessed the effectiveness of avidin against the Colorado potato beetle neonates in a no-choice detached leaf bioassay at 0, 17, 34, 51, 102, and 204 g avidin/ml over 12 d. The LC50 was 136 g avidin/ml (108Ð188 95% CL). The combined effects of avidin (136 g avidin/ml) with Bt-Cry3A or leptines were evaluated with neonates and third instars over 12 and 6 d, respectively. Three potato lines were used: susceptible line, a line engineered to express Cry3A from Bacillus thuringiensis, and a lineexpressing thenatural resistance factor leptines.Theadditionof avidin at theLC50 concentration signiÞcantly reduced consumption by neonates, but it did not affect consumption by third instars feeding on the susceptible line and the leptine line. Survival of neonates feeding on the susceptible line with avidin was signiÞcantly reduced compared with the susceptible line. Survival of third instars on the Bt-Cry3A with avidin was signiÞcantly reduced after 3 d compared with survival on the Bt-Cry3A, suggesting the addition of avidin may increase susceptibility to Bt-Cry3A.