Toxicities of acetogenin-based bioacaricides against two-spotted spider mite and selectivity to its phytoseiid predators

Abstract

Tetranychus urticae is the main pest of strawberry crops and can cause up to 80% of productivity losses under high infestations. Aiming to search T. urticae management alternatives compatible with eco-friendly or organic-based food production systems, this study evaluated the lethal and sublethal toxicities of formulated derivatives from Annonaceae (rich in acetogenins) against this pest species. In addition, it also evaluated the selectivity of the most promising formulation to the predatory mites Neoseiulus californicus and Phytoseiulus macropilis, which are largely applied in biological control in Brazil. Among the derivatives tested, the emulsion from the ethanolic seed extract of Annona mucosa-ESEAm (major component: acetogenin bis-tetrahydrofuran rolliniastatin-1) caused pronounced mortality of T. urticae after 120h of exposure (LC50 = 465.5mg L-1), in a comparable or superior manner to an abamectin-based synthetic acaricide used as positive control (LC50 = 1243.4mg L-1). Moreover, ESEAm exposure resulted in a significant decrease in the number of eggs laid by females and caused the most pronounced ovicidal action for T. urticae, with only 5% embryonic viability. However, ESEAm also showed high toxicity to the predatory mites tested, causing 100% mortality for both species after 120h exposure, similar to abamectin. The interaction between these bioacaricides and biological control agents should be tested under field conditions to further assess the potential ecological selectivity of these derivatives.