Toxicity and risk assessment of pesticides on the predatory mite, Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) under laboratory conditions

Amblyseius swirskii Athias-Henriot (Parasitiformes: Phytoseiidae) is one of the most common predatory mite species naturally occurring in several crops including citrus and vegetables in certain areas of the Mediterranean basin. Despite its abundance, and importance in sustainable pest management programs, there has been a notable gap regarding the compatibility of reduced-risk pesticides with this predatory mite. Hence, it is crucial to clarify the toxic effects of pesticides to assess the potential risk they pose to this predator and understand their environmental impact. Therefore, we evaluated the toxic effects of the six “reduced risk” pesticides, fosetyl-Al, prothioconazole + spiroxamine, proquinazid, tebuconazole, spinetoram and spinosad on different developmental stages of A . swirskii . To construct the possible “worst-case scenario”, the test units were sprayed at the maximum recommended concentrations of the pesticides. The results indicate that spinetoram, spinosad and proquinazid are highly toxic, which respectively caused 81.20%, 64.98% and 43.34% mortality on eggs, 100.00%, 100.00% and 96.66% on larvae, and 100.00%, 100.00% and 90.00% on adult females. While fosetyl-Al, prothioconazole + spiroxamine, and tebuconazole are harmless to eggs, they are moderately toxic to larvae and adult females with mortality rates respectively reaching 23.64%, 32.00% and 26.66% for larvae and 21.66%, 29.16% and 19.16% for adult females. Although all pesticides significantly reduced the egg production, higher effects were observed with application of spinetoram, spinosad, prothioconazole + spiroxamine and proquinazid. Therefore, the moderately toxic pesticides fosetyl-Al, prothioconazole + spiroxamine and tebuconazole may be compatible with A . swirskii in IPM programs. However, further investigations are essential to determine whether the highly toxic effects of other pesticides are consistent in semi-field and/or field conditions.