Potential of adjuvants and an entomopathogenic fungus for the management of Helicoverpa armigera.

Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) is a polyphagous species that feeds on crops of high economic importance in Brazil. Biological control, a component of Integrated Pest Management (IPM), employs parasitoids, predators, and entomopathogenic fungi to control agricultural pests as a strategy to reduce insecticide use and promote more sustainable practices. Adjuvants and activators, including vegetable oils, mineral oils, and fusel oil, can enhance the efficacy and toxicity of bioinsecticides. Thus, the objective of this study was to evaluate the effects of different adjuvants and the entomopathogenic fungus Metarhizium rileyi on Helicoverpa armigera larvae. The treatments consisted of sterile distilled water, fusel oil, and commercial adjuvants (Aureo®, Nimbus®, and Protac®) at different concentrations, in addition to the application of M. rileyi (1×109 conidia mL-1). Two milliliters of each treatment was applied to each replicate using a Potter spray tower. Cumulative daily mortality percentage and efficacy were calculated using Abbott's formula. All data were subjected to analysis of variance (F-test), and the means were compared using the Scott-Knott test at a 5% significance level. The adjuvants Nimbus® and Aureo® at all tested concentrations, and fusel oil at 1.5%, resulted in larval mortality rates exceeding 80% by day 6 post-application. Regarding efficacy, except for fusel oil at the lowest concentration, the other treatments showed values above 80%. Therefore, efficacy was considered more relevant than cumulative mortality, as it accounts for mortality and more accurately reflects treatment effectiveness.