FREQUÊNCIAS DE APLICAÇÃO DE BACILLUS THURINGIENSIS NO MANEJO DE SPODOPTERA FRUGIPERDA NA CULTURA DO MILHO EM HIDROLÂNDIA

Abstract

The fall armyworm (*Spodoptera frugiperda*) is one of the main pests of maize (*Zea mays* L.) in Brazil, potentially causing significant yield losses and posing management challenges due to the evolution of resistance to insecticides and certain Bt technologies. In this context, bioinsecticides based on *Bacillus thuringiensis* (Bt) represent an alternative for diversifying control strategies, making it important to evaluate different application programs under field conditions. The present study aimed to evaluate the efficacy of different application frequencies and intervals of *B. thuringiensis* var. *kurstaki* for the management of *S. frugiperda* in maize, comparing its performance with chemical treatment using deltamethrin and an untreated control. The experiment was conducted in Hidrolândia, Goiás, Brazil, from February to May 2025, in a randomized complete block design with six treatments and four replications. Leaf damage was assessed using the Davis scale (0–9) at 30 and 55 days after emergence (DAE), as well as grain yield. No significant differences were detected among treatments for leaf damage, according to the Friedman test, or for grain yield, according to analysis of variance. In the final assessment, the weighted mean damage scores ranged from 0.00 to 0.14, while mean grain yield ranged from 9,049 to 10,448 kg ha⁻¹. Increasing the number of applications of *B. thuringiensis* var. *kurstaki* from two to up to four applications, as well as reducing the interval between sprays from 15 to seven days, did not provide statistically detectable benefits for the evaluated variables. Likewise, the chemical treatment with deltamethrin did not show statistical superiority over the different bioinsecticide application programs, either for leaf damage or grain yield, indicating statistically similar performance among the strategies under the evaluated conditions. However, the low infestation intensity of *S. frugiperda* during the experimental period probably limited the ability to discriminate among treatments and does not allow absolute equivalence to be established between the control methods. The results reinforce the potential of *B. thuringiensis* var. *kurstaki* as a tool to be integrated into Integrated Pest Management programs, contributing to the diversification of control strategies, the reduction of exclusive reliance on synthetic insecticides, and the management of *S. frugiperda* resistance.