Hirsutella thompsonii offers an ecofriendly solution to manage Polyphagotarsonemus latus in mulberry

Cultivation of mulberry, Morus alba, a key component of sericulture, has seriously been hampered in the last couple of years by an unprecedented incidence of the broad mite, Polyphagotarsonemus latus, in Karnataka, Tamil Nadu and Andhra Pradesh states of India. While chemicals, such as propargite or fenazaquin, aside from sulphur, are often used to manage this pest, environmental and health concerns, besides residual toxicity to the silkworm, Bombyx mori, warrant the development of an ecofriendly and sustainable solution to the problem. The acaropathogenic fungus Hirsutella thompsonii [MF(Ag)66], unformulated and formulated, was tested against the broad mite on detached mulberry leaves in the laboratory (proving Koch’s postulates), and on potted mulberry plants under open and greenhouse conditions. Complete mortality was achieved within 72 h in the laboratory, while it took 72–96 h to achieve 90–100% mortality on potted plants. Based on the encouraging results obtained under all the conditions, five field trials were conducted during August–November 2019 in Ramanagara district of Karnataka to evaluate the fungus in the form of a mycelial–conidial formulation, 1% of which was sprayed thrice at weekly intervals. The fungus not only outperformed the chemicals used alongside in the evaluation but also spread to a considerable distance, thus causing a widespread epizootic in the mite population within a week of treatment.