Evaluation of Conidia-Dust Formulation of the Entomopathogenic Fungus, Metarhizium anisopliae to Biocontrol the Brown-Banded Cockroach, Supella longipalpa F

Background: The brown-banded cockroach Supella longipalpa (F.) as a mechanical vector of pathogens and source of allergens has recently become widespread in the city of Ahvaz, southwestern Iran. Objectives: This research was done to evaluate the efficacy of a dust-formulation of Metarhizium anisopliae isolate IRAN 437C, as a common entomopathogenous fungus, against S. longipalpa. Materials and Methods: Conidia dust-formulations of M. anisopliae were prepared in proportions of 1%, 5%, 10%, 25%, 50% and 100% with bad wheat flour as the carrier. Cockroaches were exposed to surfaces treated with 1.5 mg/cm2 of the formulations under laboratory and semi-field conditions. Results: Cockroach mortality rates increased and survival times (ST50) decreased with an increased proportion of conidia from 1% to 100% but records taken for mortality and survival time from proportions of 25%, 50% and 100% were not significantly different. The mortality rates reached 100% and 90-100% in adults and nymphs, respectively on the seventh day. The lowest ST50 was related to the proportion of 100% (3 days). Probit analysis indicated LD50 and LD90 values of 1.7 × 106 and 1.7 × 107 conidia/cm2 for adults and these values changed to 4.5 × 106 and 2.9 × 107 for third and fourth instar nymphs at three days post exposure. Proportion of 25% caused mortality rates of 87%, 81% and 73% in adult, adult nymph and nymph populations, respectively at four days after exposure under room conditions. Conclusions: Conidia dust-formulation of M. anospliae isolate IRAN 437C could present a promising alternative to control the brown-banded cockroach.