Efficacy of Selected Fungicides Against Chalkbrood of the Leafcutting Bee

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Abstract
Nine fungicides were tested for efficacy against chalkbrood (Ascosphaera aggregata) and for toxicity to larvae and prepupae of the leafcutting bee Megachile rotundata. Only Benlate at 1·0% active ingredient (a.i.) and carbendazim at 1·0 and 0·1% a.i. in the diet reduced the incidence of chalkbrood in larvae challenged with 105spores while exhibiting no toxic effects on larval or prepupal survival. Captan (Orthocide) was lethal at 1·0% a.i. and significantly reduced survival to prepupae at 0·1% without reducing the incidence of chalkbrood significantly. Captan at 0·1% a.i. also extended the number of days required for development of larvae to prepupae by over 40%.