The potential of Metarhizium anisopliae (Metschinkoff) and Hirsutella thompsonii Fisher as biological control agents of the parasitic mite, Varroa destructor (Anderson and Trueman) was evaluated in the laboratory, in observation hives, and in an apiary. Time required for 90% cumulative mortality of mites (LT90) was 4.16 (3.98-4.42) days for H. thompsonii and 5.85 (5.48-7.43) days for M. anisopliae at 1.8 x 108 conidia mm-2. At temperature similar to that of the broodnest in a honey bee colony, H. thompsonii (LD90=1.68 x 107 conidia mm-2 at day 7) and M. anisopliae( LD90=1.29 x 109 conidia mm-2 at day 7) showed a high level of pathogenicity to V. destructor. The applications of fungal pathogens to observation hives resulted in significant mortality of mite populations, and reduction of the number of mites per bee for 21 and 42 days post-treatments.
Similarly, treating field bee hives with M. anisopliae spores using both dusts and strips coated with the fungus resulted in satisfactory control of mite populations. These fungal treatments were as effective as fluvalinate (ApistanŽ), even 42 days after applications. In addition, the fungal pathogens had no harmful effects on the honey bees and did not affect the fecundity of queen. The abilities of these fungi to adapt to heat tolerance and therefore to temperature in bee hives made them strong candidate for successful biological control agents for the Varroa mites.
Species 1: Acari Varroidae Varroa destructor (Varroa mite)
Keywords: insect pathogen, Control strategy
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