Laboratory evaluation of a native strain of Beauveria bassiana for controlling Dermanyssus gallinae (De Geer, 1778) (Acari: Dermanyssidae)

- A “native” strain of B. bassiana is highly virulent toward D. gallinae.
- The B. bassiana suspension of 109 conidia/ml is highly virulent toward D. gallinae.
- The 100% mortality for adults of D. gallinae within 12 days post infection.
- B. bassiana may be effective in controlling mite populations in the environment.

The poultry red mite, Dermanyssus gallinae (De Geer, 1778) (Acari: Dermanyssidae) is one of the most economically important ectoparasites of laying hens worldwide. Chemical control of this mite may result in environmental and food contamination, as well as the development of drug resistance. High virulence of Beauveria bassiana sensu lato strains isolated from naturally infected hosts or from their environment has been demonstrated toward many arthropod species, including ticks. However, a limited number of studies have assessed the use of B. bassiana for the control of D. gallinae s.l. and none of them have employed native strains. This study reports the pathogenicity of a native strain of B. bassiana (CD1123) against nymphs and adults of D. gallinae. Batches of nymph and adult mites (i.e., n = 720 for each stage) for treated groups (TGs) were placed on paper soaked with a 0.1% tween 80 suspension of B. bassiana (CIS, 105, 107 and 109 conidia/ml), whilst 240 untreated control mites for each stage (CG) were exposed only to 0.1% tween 80. The mites in TG showed a higher mortality at all stages (p < 0.01) when compared to CG, depending on the time of exposure and the conidial concentration. A 100% mortality rate was recorded using a CIS of 109 conidia/ml 12 days post infection (DPI) in adults and 14 DPI in nymphs. B. bassiana suspension containing 109 conidia/ml was highly virulent towards nymph and adult stages of D. gallinae, therefore representing a possible promising natural product to be used in alternative or in combination to other acaricidal compounds currently used for controlling the red mite.