Michigan leads the US in production of potatoes processed into chips. Pythium Leak is the leading cause of storage losses in US potato production. Wet and warm conditions promote germination of zoospores in the soil where after the harvesting processes cause wounds or bruises, creating entry points for P. ultimum infection post-harvest. Continued use of metalaxyl or mefenoxam against populations of Pythium spp. in potato rotations cause concern for resistant to these fungicides. Six treatments were evaluated using the cv. Silverton Russet in South-West Michigan. First year data supported statistically higher disease incidence with Tifi MaxTM, Trichoderma atroviride, compared to plots treated with Ultra FlourishTM. After plot replication, year two data were unable to show any statistical differences between treatments on agronomic attributes or disease incidence. Further in-vitro Pythium spp. sensitivity assays were conducted with these treatments. The Orondis GoldTM treatment resulted in the lowest EC50 which could not be calculated at the lowest level 0.01 ppm because it inhibited all Pythium spp. growth. Next, Ultra FlourishTM reduced half the Pythium spp. growth at 0.32ppm. The least effective treatments at reducing pathogen growth were EluminTM or Previcur FlexTM, both resulting with EC50 values of 1.9 ppm and 7.9 ppm respectively. Five days post transfer Trichoderma atroviride overtook the Pythium spp., providing support as a possible biological suppression tool.
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