Parasitoides de ovos associados à Spodoptera frugiperda no Cerrado Maranhense: ocorrência, desempenho biológico e seletividade a inseticidas

Abstract

The fall armyworm, Spodoptera frugiperda (J.E. Smith, 1797), stands out as the main pest of maize in Brazil, causing high yield losses and high investment in the use of chemical insecticides, which favors the selection and development of resistant populations. Therefore, biological control with egg parasitoids represents a promising alternative for Integrated Pest Management. This study aimed to evaluate the potential of egg parasitoids in the management of S. frugiperda in the Cerrado of Maranhão, investigating the natural occurrence of these species, their biological performance as a function of host egg density and age, as well as the selectivity of insecticides used in maize cultivation. Egg masses were collected in commercial maize areas during the 2023/2024 and 2024/2025 growing seasons, with subsequent morphological and molecular identification of the collected parasitoids. Under controlled laboratory conditions, bioassays were conducted to evaluate parasitism, emergence, and sex ratio at different densities and embryonic ages of the eggs. Additionally, insecticides recommended for the crop were applied at two exposure periods, before and after egg parasitism, and their effects on biological parameters and parasitism preference behavior were evaluated. Data were submitted to analysis of variance (ANOVA), and means were compared at a 5% probability level. The natural occurrence of Telenomus remus and Trichogramma pretiosum parasitizing S. frugiperda eggs in the Cerrado of Maranhão was recorded. The first record of Te. remus in the region was obtained; this same species showed higher parasitism efficiency, especially on eggs up to 24 hours old and at intermediate densities, resulting in higher parasitism and emergence rates. Insecticide selectivity varied according to the active ingredient and application timing, with negative effects on parasitism, emergence, and sex ratio observed in certain treatments, evidencing a potential impact on the efficiency of both biological control agents recorded. It is concluded that the egg parasitoids Te. remus and Tr. pretiosum have high potential for integration into S. frugiperda management programs in the Cerrado of Maranhão. However, compatibility with insecticides must be carefully considered to preserve the efficiency of these natural enemies and contribute to the sustainability of maize production systems.