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)

Tomato russet mite, Aculops lycopersici is considered one of the most important crop pests globally. The main control strategy is based on synthetic acaricides which, however, create resistant strains and ecological risks. In this context, biopesticides could be a viable and sustainable alternative for the 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 Ragusa under laboratory conditions. Six concentrations were tested for each product against A. lycopersici adults (0, 320, 640, 1280, 2500 and 5000 μL L-1), and the median concentration (1280 μL L-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 μL L-1for carlina oxide and 253.79 μL L-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.