Biological control of fusarium dry rot of potato tubers under commercial storage conditions

Lack of effective chemicals impedes control of Fusarium dry rot of stored p otato tubers destined for processed and table stock use, Biological control of dry rot incited by Gibberella pulicaris (anamorph=Fusarium sambucinum) has been demonstrated in laboratory studies but not in commercial storage e nvironments. Several Gram-negative bacterial strains that were efficacious and amenable to production in liquid culture in laboratory studies were sel ected for pilot studies in Idaho and for bin trials at commercial storage h ouses in Idaho and North Dakota. In the first year of pilot studies, Pseudo monas fluorescens S22:T:04 (approximate to 1 x 10(8) cfu/ml) decreased dry rot caused by G. pulicaris by 19% when coinoculated with the pathogen compa red to controls and to the fungicide thiabendazole (TBZ) applied at label r ates, In second year pilot studies, P, fluorescens P22:Y:05 and Enterobacte r cloacae S11:T:07 (approximate to 4 x 10(8) cfu/ml) reduced the severity o f disease incited by G. pulicaris (25% and 17% average disease decrease, re spectively) when antagonists were applied after pathogen inoculum, Treatmen t effects on dry rot that developed from inoculation with Nectria haematoco cca (anamorph=Fusarium solani var, coeruleum) were variable and influenced by interactions between antagonists, a wetting agent, and TBZ. In commercia l storage bin trials, E. cloacae S11:T:07 reduced naturally occurring level s of dry rot by an average of 21% compared to 14%;, for TBZ, demonstrating that this antagonist was effective when produced using a liquid culture med ium and methodology that approximates commercial practices for producing bi omass.