Effects of thuringiensin on European red mite (Acarina: Tetranychidae) mortality, oviposition rate and feeding

Abstract

Effects of two formulations of thuringiensin (ABG-6162A and ABG-6266) on mortality, oviposition rate, and feeding of European red mite, Panonychus ulmi (Koch) were evaluated. Mite toxicities of the formulations were not significantly different. Immature instars were significantly more susceptible than adults. Low mortality of all instars was recorded after 3 d, indicating slow activity. The relationship between log (concentration + 1) of ABG-6162A and ABG-6266 and P. ulmi oviposition rate was best described by fourth-order polynomial equations, suggesting that thuringiensin both inhibits and stimulates P. ulmi oviposition. ABG-6162A affected oviposition at lower concentrations than ABG-6266. A quadratic relationship was observed between log (concentration + 1) of thuringiensin and P. ulmi adult female feeding. ABG-6162A reduced feeding more than ABG-6266 at concentrations ⩾ 1 mg liter−1. Toxicity to immatures and the sublethal effects described suggest that thuringiensin may control field populations of P. ulmi despite low initial mortality.