Side effects of pesticides used in organic and conventional tomato crops on Dolichogenidea gelechiidivoris, a parasitoid of Tuta absoluta.

BACKGROUND

Dolichogenidea gelechiidivoris is a key biological control agent of Tuta absoluta, one of the most destructive pests in tomato crops worldwide. As part of integrated pest management (IPM) programs, pesticides are commonly applied to control multiple pests. However, their compatibility with parasitoids such as D. gelechiidivoris remains poorly understood. This study evaluated the impact of eight commonly used pesticides on D. gelechiidivoris through four exposure routes relevant to field conditions.

RESULTS

Among the pesticides tested, spinosad and cyantraniliprole were the most toxic, causing up to 90% adult mortality via fresh residues and topical exposure. These compounds also showed high ingestion toxicity and completely suppressed parasitoid emergence from parasitized hosts. Conversely, sulfur, spiromesifen and spirotetramat had a low impact on adult survival, and allowed parasitoid emergence rates similar to the control. Notably, Bacillus thuringiensis significantly reduced female egg load without increasing adult mortality, indicating a sublethal reproductive effect. Overall, pesticide impact varies depending on the exposure route, with contact and topical exposure generally leading to higher mortality than ingestion or effects on immature stages.

CONCLUSION

This study highlights substantial variation in the side effects of IPM-compatible pesticides on D. gelechiidivoris. While some products were highly disruptive, others proved more selective and compatible with biological control. These findings support more informed pesticide selection in tomato IPM, balancing effective T. absoluta control with the conservation of key parasitoids. © 2025 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.