Evaluation of Various Spray Nozzle and Volume Combinations for Control of Colorado Potato Beetle (Coleoptera: Chrysomelidae) with Synthetic and Biological Insecticides

Abstract

Field experiments were done in potatoes, Solanum tuberosum L., to evaluate various spray nozzle and volume combinations for control of Colorado potato beetle, Leptinotarsa Decemlineata (Say), with synthetic insecticides and Bacillus thuringiensis . Colorado potato beetles were moderately tolerant to permethrin, and use of hollow-cone nozzles resulted in improved control compared with flat-fan nozzles. When flat-fan nozzles were used with permethrin, increasing spray volume from 103 to 298 Iiter/ha resulted in a reduction in defoliation and an increase in tuber yield. Colorado potato beetles were highly susceptible to esfenvalerate. Nozzle type and spray volume had no significant effect on insect density or defoliation. However, a significant linear relationship existed between Colorado potato beetle counts and esfenvalerate spray volume. On some sample dates, density of Colorado potato beetles was reduced in the high volume (467 liter fha) esfenvalerate treatment compared with the low volume (93 liter fha) treatment. Efficacy of cryolite for control of Colorado potato beetle was not significantly influenced by nozzle type or spray volume treatment. In experiments with B. thuringiensis var. san diego (M-One Insecticide), use of three hollowcone drop nozzles per row resulted in significantly lower Colorado potato beetle density and defoliation, compared with use of hollow-cone nozzles arranged over the tops of the plants. Colorado potato beetle control with B. thuringiensis was enhanced (with both nozzle treatments) by increasing spray volume from 140 to 560 liter fha.