EFFICACY OF MIXTURES OF MICROBIAL INSECTICIDES AND PERMETHRIN AGAINST THE CABBAGE LOOPER (LEPIDOPTERA: NOCTUIDAE) AND THE IMPORTED CABBAGEWORM (LEPIDOPTERA: PIERIDAE)

Abstract

The joint action of permethrin and Bacillus thuringiensis var. kurstaki Berliner (B.t.), Autographa californica (Speyer) nuclear polyhedrosis virus (ACNPV), or Artogeia (= Pieris) rapae (L.) granulosis virus (ARGV) fed as mixtures to larvae of Trichoplusia ni (Hübner) or A. rapae in laboratory bioassys differed with the host insect, the components, and the concentrations of the components. Permethrin interfered with the activity of ACNPV and ARGV in most of the mixtures, particularly at low concentrations of the latter virus but mortality by mixtures of mid-range (approximately LC₅₀ if fed alone) concentrations of permethrin and of ACNPV exceeded the mortality expected by the components acting independently. Concentrations of permethrin in the middle of the dosage range enhanced the effect of B.t. against T. ni resulting in mortality that exceeded the expected mortality but mortality of A. rapae larvae fed most permethrin–B.t. mixtures was less than expected.