Postharvest Control of Fusarium Dry Rot Using Biological Control and Chemical Combinations
Extension, Production and Management
Tuesday, July 21, 2020
2:45 PM - 3:05 PM
Patricia J. Slininger National Center for Agricultural Utilization Research  
Nora Olsen University of Idaho  
Jeff S. Miller Miller Research  
David A. Schisler National Center for Agricultural Utilization Research  
Lynn Woodell University of Idaho  
Andrew Hollingshead University of Idaho  
Maureen A. Shea-Andersh National Center for Agricultural Utilization Research  
Andrew R. Schoepke National Center for Agricultural Utilization Research  
Bruce S. Dien National Center for Agricultural Utilization Research


Postharvest Fusarium dry rot of potatoes is a serious problem worldwide.  StadiumTM (difenoconazole, azoxystrobin and fludioxonil) and Graduate A+TM (azoxystrobin and fludioxonil) show promise in reducing dry rot, and desiccation tolerant variants of three biocontrol strains of Pseudomonas sp. have been developed to have improved storage stability in dry formulations.  When produced in triculture, this biological control agent (BCA) suppresses Fusarium dry rot decay, late blight, pink rot, Pythium leak and sprouting in storage, and adds multiple control mechansims to minimize risk of pathogen resistance.  Experiments were designed to assess dry rot suppression by BCAs alone and in combination with Graduate or Stadium or 1/3 label Stadium applied to Clearwater Russet and Russet Burbank cultivars.  In 24-72h laboratory assays the BCA rehydrated and survived well in mixture with the fungicides. In wounded potato assays, 10 tubers per treatment were inoculated with a conidial suspension of Fusarium sambucinum, then allowed to set covered 45 minutes, then wounded on opposite sides with a 2mm (length x diameter) blunt steel post and sprayed at 0.1 mL/oz tuber with fungicides or BCAs.  Significant disease reduction (67-81%) was observed for BCA alone (grown on either synthetic or lower cost switchgrass hydrolysate, respectively).  A lower disease reduction (49%) was observed, when the BCA was applied double strength at half volume (0.05 mL/oz tuber).  Near complete disease prevention (91-95%) occurred when the BCA was used in combination with Stadium, 1/3 label Stadium, and Graduate, and with chemicals used alone (94-97%).  Disease control did not vary significantly among different chemical applications with or without BCA present, or whether applied at 0.05 or 0.1 mL/oz tuber.  Additional bioefficacy data from a similar small pilot experiment (80 tubers per treatment) in progress will be presented and compared for consistence with performance of like treatments tested in a prior year.