The South American tomato pinworm, Tuta absoluta (Meyrick), is native to the western Neotropics. After invading Spain in 2006, it spread rapidly throughout Afro-Eurasia and has become a major threat to world tomato production. Integrated pest management (IPM) strategies have been developed, but widespread insecticide use has caused selection for insecticide resistance as well as undesirable effects on key beneficial arthropods. Augmentation and conservation biological control relying on omnivorous mirid predators has proved successful for management of T. absoluta, where implementation is dependent on abiotic, biotic (e.g., alternative prey), and anthropogenic factors (e.g., pesticides). Research has been carried out on larval parasitoids, showing potential for further development of sustainable control. The development of resistant tomato varieties is ongoing, but they are not commercially available yet. Knowledge gaps remain to be filled to optimize IPM packages on tomato crops and to help prevent further spread worldwide.

Pesticide risk assessments are usually based on short-term acute toxicity tests, while longer-term population dynamic related traits, critical to the success of biological control and Integrated Pest Management (IPM) programs, are often overlooked. This is increasingly important with respect to new biopesticides that frequently cause no short-term acute effects, but that can induce multiple physiological and behavioral sublethal effects, leading to a decrease in population growth and ecosystem services. In this study we assessed the lethal and sublethal effects of six biopesticides [abamectin, azadirachtin, Bacillus thuringiensis, borax plus citrus oil (Prev-Am®), emamectin benzoate, and spinosad], used in tomato crops to control the invasive pest Tuta absoluta (Lepidoptera: Gelechiidae), on adults and pupae of the parasitoid Bracon nigricans (Hymenoptera: Braconidae). Data on female survival and production of female offspring were used to calculate population growth indexes as a measure of population recovery after pesticide exposure. Spinosad caused 100% and 80% mortality in exposed adults (even 10 d after the treatment) and pupae, respectively. Although most of the biopesticides had low levels of acute toxicity, multiple sublethal effects were observed. The biocontrol activity of both females that survived 1-h and 10-d old residues, and females that emerged from topically treated pupae was significantly affected by the application of the neurotoxic insecticides emamectin benzoate and abamectin. Furthermore, very low B. nigricans demographic growth indices were estimated for these two insecticides, indicating potential local extinction of the wasp populations. Among the tested products, Bt proved to be the safest for B. nigricans adults and pupae. Our findings emphasize that acute toxicity assessment alone cannot fully predict the actual impact of pesticides on non-target parasitoids. Thus, sublethal effects related to the species specific life-history variables must be carefully considered in order to assess pesticide risks and to incorporate new pesticides, including biopesticides, into IPM programmes.