Bioatividade de bactérias e vírus para Spodoptera frugiperda (Lepidoptera: Noctuidae)

Abstract

Spodoptera frugiperda is an agricultural pest present in several crops, and it can also be present throughout the entire cultivation cycle, the biological control method has been used in the management of this pest. The objective of this work was to evaluate the bioactivity of bacteria and viruses in the management of S. frugiperda, under laboratory conditions. For the bioassays, 6 treatments were used T1: Control (without the application of biological products), T2: entomopathogenic virus Spodoptera frugiperda multiple nucleopolyhedrovirus - SfMNPV, T3: Autographa californica multiple nucleopolyhedrovirus - AcMNPV, T4: Bacillus subtilis, T5: Bacillus thuringiensis subsp. thoworthy, T6: Bacillus thuringiensis subsp. kurstaki. Each treatment consisted of 5 repetitions containing 6 caterpillars each, for 2nd and 3rd instars. Bioinsecticides and biofungicide were applied in full dose as recommended in the package insert, with the aid of the Potter tower. Mortality was assessed daily until they completed the larval cycle. The confirmed accumulated mortality data were submitted to analysis of variance (F test), the means were compared by Scott-Knott test at 5% probability and the efficiency of the biopesticides using the Abbott formula, after ten days of application. For 2nd instar caterpillars SfMNPV and B. subtilis provided 100% mortality, for 3rd instar caterpillars AcMNPV and B. subtilis provided 90 and 80% mortality, respectively, but in this instar there was a lower mortality than in the 2nd instar. Some hypotheses can be considered to explain the fact that the maximum efficiency was below 76.67% for 3rd instar caterpillars, in addition to the caterpillars' own immune system, the pH of the midgut should be alkaline, as the more advanced the instar more acid will be, decreasing the action of microorganisms.