Combined application of predatory mites and fungal pathogens for biological control of Brevipalpus yothersi (Acari: Tenuipalpidae) under laboratory conditions

• Brevipalpus yothersi is the vector of the Citrus leprosis virus. • B. yothersi was susceptible to infection by fungal pathogens. • Eggs were the preferred prey of the predatory mites Neoseiulus californicus and Amblyseius swirskii , followed by nymphs and then larvae . • Predatory mites contaminated with fungal conidia achieved greater B. yothersi mortality than predatory mites alone. • Combined use of predatory mites and fungal conidia could represent a more efficient biological control strategy for B. yothersi . The mite Brevipalpus yothersi (Baker) (Acari: Tenuipalpidae), vector of Citrus leprosis virus, is typically controlled using synthetic pesticides. However, alternative control strategies are required to reduce pesticide use for more sustainable citrus production. The mortality of B. yothersi following combined application of fungal pathogens and predatory mites was evaluated. First, we quantified susceptibility of B. yothersi adults to infection when treated with conidial suspensions (1 × 10 8 conidia mL −1 ) of three fungal isolates, Bb88 ( Beauveria bassiana ), Ma129 ( Metarhizium anisopliae ) and Pfr4 ( Cordyceps fumosorosea ). Then, we evaluated the feeding preference (choice and no choice) of the predatory mites Neoseiulus californicus and Amblyseius swirskii for eggs, larvae, nymphs and adults of B. yothersi . In addition, we evaluated the searching capacity of both predators when foraging for eggs of B. yothersi . Finally, the mortality of B. yothersi adults exposed to predatory mites contaminated with conidia of two fungal isolates was determinated. Isolates Bb88 and Ma129 caused the highest mortality in B. yothersi . Both predatory mites preferred to consume eggs, followed by larvae and then nymphs, but not adults of B. yothersi, in both experiments (choice and no choice). The predatory mite A. swirskii had a greater search capacity than N. californicus . The greatest mortality of B. yothersi adults was achieved when predatory mites contaminated with conidia were used (especially isolate Ma129 [approx. 80%]), compared with treatments of predatory mites alone (approx. 35%). The predatory mite A. swirskii and the fungus M. anisopliae (Ma129) was the most promising combination for further evaluation for biological control of B. yothersi .