Lethal and Sublethal Effects of Carlina Oxide and Acmella oleracea Extract Enriched in N-Alkylamides on Aculops lycopersici (Acari: Eriophyidae) and Its Predator Typhlodromus exhilaratus (Acari: Phytoseiidae) in Laboratory Tests

The tomato russet mite, Aculops lycopersici, is considered one of the most important crop pests globally. The main control strategy is based on synthetic acaricides: however, they create resistant strains and ecological risks. In this context, biopesticides could be a viable and sustainable alternative for eriophyid control. In the present study, the toxic effects of a N-alkylamides-enriched extract obtained from Acmella oleracea and of carlina oxide, the main bioactive component of Carlina acaulis, on A. lycopersici were evaluated, as well as their side effects on the phytoseiid Typhlodromus exhilaratus under laboratory conditions. Six concentrations were tested for each product against A. lycopersici adults (0, 320, 640, 1280, 2500, and 5000 &mu:L L&minus:1), and the median concentration (1280 &mu:L L&minus:1) was evaluated against eggs and females of the phytoseiid T. exhilaratus. Both the N-alkylamides-enriched extract and carlina oxide showed total lethal effects (100% of mortality) towards A. lycopersici at the two highest concentrations. Moderate-to-high mortality was also recorded with the lower concentrations: from 42.22 to 97.78%. Probit analysis identified LC50 values of 205.32 &mu:L L&minus:1 for carlina oxide and 253.79 &mu:L L&minus:1 for the N-alkylamides-enriched extract, respectively. Carlina oxide showed a moderate ovicidal effect on T. exhilaratus eggs (50.00% hatching rate) on T. exhilaratus, and caused 39.13% mortality on females, whereas the N-alkylamides-enriched extract was less toxic, with a hatching rate of 88.00% and a mortality rate of 18.75% on females. In conclusion, carlina oxide and the N-alkylamides-enriched extract showed high toxicity on A. lycopersici, with a reduced effect on phytoseiid. These results highlight the potential of these products as sustainable means for the management of tomato russet mite.