In vitro compatibility of Isaria fumosorosea from Bemisia tabaci with four commonly used fungicides in vegetable production

Abstract

Isaria fumosorosea is an entomopathogenic fungus used for controlling insect pests, especially the sweet potato whitefly, Bemisia tabaci. To use this fungus as part of an Integrated Pest Management (IPM) programme its compatibility with pesticides, particularly fungicides, must be determined. The effects of the most commonly used fungicides viz., Bellis® (Pyraclostrobin+Boscalid), Carbendazim, Phyton 27® (Copper sulfate) and Ridomil Gold® (Metalaxyl+Mancozeb) at concentrations of 0.01, 0.1, 1.0, 10 and 100mg/L were evaluated for compatibility with I. fumosorosea in the current study. Colony radius (mm), colony radial growth rate Kr (mm/h) and time for 50% germination (GT50) (h) were analysed using linear regression analysis whereas relative growth was assessed by vegetative growth which was measured through the colony rate growth in potato dextrose agar (PDA). Colony radius increased with time for all fungicide concentrations at all temperatures (25, 28 and 300C) tested. Inhibition was measured as fungal growth in treated compared to untreated in PDA (= relative growth, RG). All fungicides except Bellis at the highest concentration were compatible (RG > 50) with I. fumosorosea at the three temperatures tested. Colony radial growth rate (Kr) was the greatest at 25oC for all concentrations of fungicide and temperatures tested. GT50 generally increased with increasing fungicide concentrations and temperatures.