INSECTICIDE RESISTANCE OF TOMATO BORER Tuta absoluta (MEYRICK) UNDER EGYPTIAN CONDTONS

The efficacy of five insecticides [organophosphate (methamidophos), carbamate (methomyl), pyrethroid (Deltamethrin), spinosad (spintor) and imidaclopride (Confidor)] were determined against four strains of Tuta absoluta collected from four governorates in Egypt [Damytta (DAM), Marsa Matrouh (MAR), Behera (BEH) and Kafer El-Sheikh (KAF)]. Collected strains were bioassayed and compared with a reference susceptible strain. Insecticides were dissolved in acetone and topically applied to the mid-dorsal abdominal region of two-day old 4th instar larvae. LD50 values were estimated and the Resistance Factor (RF) for each insecticide was calculated (RF = LD50 value of each field strain / LD50 value of the susceptible strain). DAM and MAR strains recorded 29.72 and 10.62-fold resistance, respectively to methamidophos. DAM and MAR strains recorded 32.53 and 10.76-fold resistance, respectively to methomyl. DAM and MAR strains demonstrating 70.81 and 28.09-fold resistance, respectively to deltamethrin. DAM and MAR strains recorded 38.04 and 17.08-fold resistance, respectively to spinosad, while KAF and BEH strains demonstrated 14.92 and 12.14-fold resistance, respectively to confidor. These results are discussed in relation to the possible mechanisms of resistance present in the studied T. absoluta strains and underpin the resistance management strategy for the tomato borer in Egypt.