Effects of selected fungicides on in vitro spore germination and vegetative growth of Ascosphaera aggregata

Abstract

Five fungicides were studied for their effects on Ascosphaera aggregata, the causative organism of chalkbrood in the alfalfa leafcutter bee Megachile rotundata. EC50s for inhibition of vegetative growth on an agar surface were: enilconazole, 0.034; Rovral (iprodione), 1.10; Benlate (benomyl), 1.16; and Ascocidin (N- glycosylpolifungin), 135.6 ppm (m/v). DFMO (α-DL-difluoromethyl omithine) stimulated growth resulting in c50% increased radius at 10 000 ppm compared to the control. Benlate inhibited spore germination; at the highest concentration only, Rovral inhibited germination while Ascocidin and enilconazole exhibited a slight effect. DFMO did not affect spore germination. Compounds with activity against spore germination or germling viability may be the most promising candidatates for use against chalkbrood. -from Authors