The Effects of Indoxacarb and Methoxyfenozide against Colorado Potato Beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae)

In this study, lethal effects of indoxacarb and methoxyfenozide were assessed on Colorado potato beetle. To do the bioassays, potato leaflets were dipped in aqueous suspensions of the insecticides and the larvae were transferred on the leaflets after drying. The results were recorded 24 and 72h after treatment for indoxacarb and methoxyfenozide, respectively. LC50 of methoxyfenozide for the 1st instars was 80.6 mg ai/l and LC50 values for indoxacarb were 4.5, 6.85, 9.42 and 7.28 mg ai/l for 1st, 2nd, 3rd and 4th instars, respectively. LC50 value of methoxyfenozide for 1st instar was relatively high; therefore lethal concenteration was not estimated for next instars. Because of the importance of sublethal effects in insect growth regulators (IGRs) application, the sublethal effects were evaluated for methoxyfenozide by using its LC1 and LC7. First instars were fed on treated leaves for 48 or 96h and then on untreated leaves; and were monitored until adult stage. Fecundity of these adults was evaluated. The number of larvae developed to prepupae and adults was significantly lower in sublethal concentrations of methoxyfenozide compared with control. The treated larvae did not reach next generation. The results indicated that indoxacarb and methoxyfenozide were effective against Colorado potato beetle; and if they perform equally well in the field, they can be suitable candidates for management of this important pest.