Aerial Concentrations of Pathogens Causing Early Blight and Brown Spot Within Susceptible Potato Fields.

Early blight caused by and brown spot caused by are two common foliar diseases of potato, with early blight typically predominating in incidence and severity. Renewed interest in these two diseases has arisen as a result of notable differences in fungicide resistance profiles of the pathogens and inconsistent outcomes of disease management tactics. The pathogens share similar disease cycles, but they differ in the shape and size of their conidia. has a host range that includes just the Solanaceae, whereas has a broad host range spanning numerous plant families. Such differences may result in differences in dispersal of the pathogens and subsequently influence epidemiology and management outcomes. In the commercial potato fields investigated in this study, the aerial conidial concentrations of and differed significantly, with those of conidia being higher in number and more variable than those of The aerial conidial concentration of almost always significantly decreased with height (0 to 3 m above the canopy), whereas such a decrease was only observed for 4 of 12 days for . The atmospheric concentrations of were higher than those of at both upwind and downwind edges of the field ( < 0.0001), indicating more potential for long-distance dispersal. A higher aerial concentration of conidia at the downwind than the upwind location was observed for ( < 0.05), whereas overall no such effect was observed for . This indicated that the potato fields investigated were likely the source of conidia, but they may not be the sole source of . Results are consistent with inoculum of coming primarily from within the potato crop, whereas that of may be generated from diverse plant sources across the landscape.