Growth characteristics and pathogenic consequences of predominant entomopathogenic Yukon soil fungi Mortierella alpina and Penicillium expansum,and effectiveness of Met52®,against larvae of the winter tick,Dermacentor albipictus

Water activity-temperature relationships are reported for Yukon soil-isolated strains of Mortierella alpina and Penicillium expansum that are natural enemies to larvae(infestation stage)of the winter tick Dermacentor albipictus.Both fungal strains are psychrotrophs,characterized by low thermal growth ranges,consistent with their occurrence in Yukon soil.In contrast to P.expansum,M.alpina is more temperature sensitive,has a higher requirement,and is more virulent to tick larvae.Researchers and Biological Control Officers should note that for tick population control these M.alpina and P.expansum strains grow and sporulate well under moderate temperature and humid conditions.Our experiments used Met52®Bioinsecticide as a positive control,and this is the first study that demonstrates the effectiveness of this commercial product against winter tick larvae.

Entomopathogenic fungi isolated from Yukon soil against unfed larvae of the winter tick,Dermacentor albipictus

Fungal composition of Yukon soil samples consisted of 29 soil saprobes common to acidified forest,subarctic habitats.All of the fungi identified are psychrotrophs,capable of growth at both 4℃ and 20℃.Of these,a total of 17 fungi were found to be entomopathogenic by winter tick(Dermacentor albipictus)larval bioassays:Aspergillus flavus,Beauveria,namely B.bassiana,Mucor,Paecilomyces yielded>~70%larval mortality and the remainder,mostly Mortierella and Penicillium,averaged~40%larval mortality.Sites where elk(Cervus elaphus canadensis)are observed had an overall greater quantity,and diversity of entomopathogenic soil fungi than sites where elk are not observed.Greater diversity of fungi at elk-inhabited sites is likely a product of warmer soil microclimate(hillsides where elk are seen,lose snow earlier than other areas),animal presence,and increased nutrient enrichment.We conclude that Yukon soils contain fungi that naturally regulate populations of D.albipictus.All fungi are archived at the Wittenberg University Fungus Collection,Springfield,OH,USA.