Resistência de Plutella xylostella (L.) (Lepidoptera: Plutellidae) aos inseticidas de risco reduzido Xentari® e Match

Abstract

The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae) is the main pest of cruciferous plants worldwide. In the tropics and subtropics, where cruciferous plants are grown year-round, this pest may be present. Due to the rapid population growth of P. xylostella with severe overlapping generations, this pest can seriously harm plant production. To control P. xylostella, farmers often increase insecticide concentrations, increase application frequency, and mix several insecticides. These activities are strongly linked to the development of insecticide resistance in these moths. To date, P. xylostella populations have generated resistance to all molecules used against them. To overcome these problems, more and more studies are being carried out on the resistance of P. xylostella, but there are no studies in Piauí that show the response of these insects to biological insecticides and growth regulators (IGR). Therefore, the objective of this work was to verify the resistance status of P. xylostella to Bacillus thuringiensis (Bt) var. aizawai and lufenurom. The immersion method was used in bioassays to estimate the concentration-response curves for the populations of Uruçuí-PI and São Domingos do Azeitão-MA. Concentration-response curves were established for the biological insecticide XenTari® (Bt) and the growth regulator Match® EC (Lufenuron). The estimated LC50s in the study were 57,892 (41,532 – 81,232) mg/L; 77.719 (50.061 – 121.514) mg/L for Bt and 1281,304 (813.778 –1711.771) mg/L; 191,599 (145,667 – 246,533) mg/L for lufenuron in the populations of Uruçuí and São Domingos do Azeitão, respectively. The Bt-based insecticide was efficient in controlling the two tested populations of P. xylostella, but requires continuous resistance monitoring so that the useful life of this molecule is preserved for longer. The LC80 for lufenuron in both populations was high in relation to the field dose recommended by the manufacturer, and its use should be discontinued in the control of P. xylostella populations evaluated in this study.