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Title: FIELD TRIALS USING THE FUNGAL PATHOGEN, METARHIZIUM ANISOPLIAE (DEUTERMYCETES: HYPHOMYCETE) TO CONTROL THE ECTOPARASITIC MITE, VARROA DESTRUCTOR (ACARI: VARROIDAE) IN HONEY BEE COLONIES

Author
item KANGA, LAMBERT - USDA-ARS RES ASSOC
item James, Rosalind
item Jones, Walker

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/15/2003
Publication Date: 8/20/2003
Citation: Kanga, L.H., James, R.R., Jones, W.A. 2003. Field trials using the fungal pathogen, Metarhizium anisopliae (Deutermycetes: Hyphomycete) to control the ectoparasitic mite, Varroa destructor (Acari: Varroidae) in honey bee colonies. Journal of Economic Entomology. 96(4):1091-1099.

Interpretive Summary: The honey bee is of great economic importance, not only for honey production, but also for crop pollination. Each year the bee industry in the U.S. contributes to over $100 million of honey products and several billion of dollars worth in pollination of crops and vegetables. The parasitic mite, Varroa destructor, is currently the most serious threat to beekeeping as infestation of Varroa mite in North America causes annual losses of untreated colonies soaring as high as 50-80% in some areas of the United States. Apistan(R)(aau-fluvalinate) and Check-Mite(R)(coumaphos) strips are the most widely used Varroa controls in the United States and Canada. Mites throughout Europe and North America are evolving resistance to miticides, threatening the bee industry. As a result, there is an urgent need for alternative control strategies that are sustainable, cost-effective and with no mammalian toxicity. We found that the fungal pathogen, Metarhizium anisopliae, was highly pathogenic to Varroa and peak mite mortality occurred 3-4 days after the spores were applied. The mites were still infected with the fungus over 42-day post treatments. Both application methods tested (dusts and strips coated with the fungus), resulted in significant control of mite populations. The fungal treatments were as effective as the miticide, fluvalinate (Apistan(R)), at the end of the 42-day period of the experiment. Optimum mite control could be achieved during times when no brood is being produced, or when brood production is low, such as in the early spring or late fall. The fungus was harmless to the honey bees and did not have any deleterious effects on adult and young bees, or brood, and did not impede colony development. In addition, because workers and drones drift between hives, the adult bees were found to spread the fungus between honey bee colonies in the apiary, a situation that could be beneficial to beekeepers. Overall, the data supports the role of fungal pathogens as key components in an integrated pest management strategy for the control of the Varroa mite.

Technical Abstract: The potential for Metarhizium anisopliae (Metschinkoff) to control the parasitic mite, Varroa destructor (Anderson and Trueman), in honey bee colonies was evaluated in field trials. Peak mortality of Varroa mites occurred 3-4 days after the conidia were applied; however, the mites were still infected 42 days post-treatments. Two application methods were tested, dusts and strips coated with the fungus, and both methods resulted in significant control of mite populations. The fungal treatments were as effective as the miticide, fluvalinate (Apistan(R)), at the end of the 42-day period of the experiment. The data also suggested that optimum mite control could be achieved during times when no brood is being produced, or when brood production is low, such as in the early spring or late fall. Metarhizium anisopliae was harmless to the honey bees and did not have any deleterious effects on adult and young bees, or brood, and did not impede colony development. Mite mortality was highly correlated with the occurrence of mycosis in dead mites collected from sticky traps, indicating that the fungus was infecting and killing the mites. In addition, the pathogen was able to reproduce on the hosts. Because workers and drones drift between hives, the adult bees were found to spread the fungus between honey bee colonies in the apiary, a situation that could be beneficial to beekeepers.