Biological alternatives for managing peanut thrips: field evaluation of predatory mites and entomopathogenic nematodes

Thrips represent a major constraint to peanut production, particularly under organic and low-input systems where chemical options are limited. This study evaluated the field performance of biological control agents as potential alternatives for managing peanut thrips under field conditions over two growing seasons (2023/2024 and 2024/2025) under contrasting pest pressure. The biological agents included two predatory mites ( Typhlodromus transvaalensis and Stratiolaelaps scimitus ) and the entomopathogenic nematode Steinernema rarum . Thrips larvae and adults were monitored weekly and analysed using generalized linear mixed models. In both seasons, a significant interaction between treatment and time was detected for larvae and adults, indicating that treatment effects varied throughout the crop cycle. In the first season, larval density in untreated plots peaked at 6.56 ± 0.33 larvae per leaf, whereas in the second season substantially higher infestations were recorded, reaching 18.45 ± 1.07 larvae per leaf. Biological treatments consistently reduced larval densities relative to the control, particularly during the main infestation period between 25 and 60 days after sowing. Typhlodromus transvaalensis provided more immediate suppression, while Stratiolaelaps scimitus exhibited density-dependent regulation under higher pest pressure. Steinernema rarum showed moderate but consistent regulation across seasons, with performance influenced by environmental conditions and application timing, and required fewer field applications compared to predator releases. Although chemical control resulted in higher efficacy in reducing thrips populations, biological treatments maintained lower larval densities relative to the untreated control throughout the crop cycle. These findings indicate that biological agents can contribute to reducing pest pressure under field conditions and support their use as complementary components within integrated pest management (IPM) programs, particularly in organic and low-input systems.