Effects of Microclimate, Cropping Systems and Irrigation Management On Early and Late Blight Potential On Russet Burbank Potato In North-Eastern United States.

Soil and irrigation management have been used to optimize crop production; however, their effects on microclimate, development, and controls of potato diseases have not been adequately quantified. The effects of soil, crop, and water management on development of potato early blight and late blight were quantified in a potato cropping systems experiment in Maine, a cool temperate region of northeastern USA from 2006 to 2008.  Microclimate, (soil temp, air temp, relative humidity, soil water content and leaf wetness)  was not significantly impacted by cropping systems, and varied within seasons and across years. Irrigation management had little impact on microclimate, suggesting that treatment induced effects were not significant. Early blight incidence, severity, and lesion numbers were, however, impacted by management systems and years. Disease incidence was significantly (P<0.05) greater in Continuous Potato (PP) than Disease Suppressive (DS), Soil Conserving (SC), Soil Improving (SI) and Status Quo (SQ) systems. Due to fungicide applications, no late blight was recorded in field plots, however; the potential for late blight development, based on theoretical late blight indices such as hours of RH>90%, predicted area under disease progress curves (AUDPC), severity values, and blight units had similar values among cropping systems and water management. Microclimatic variables were not significantly correlated to either early blight or late blight potential, perhaps due to the small-scale size of experimental plots and influence of the surrounding environment, or lack of significant treatment effects. In addition to the positive attributes often associated with potato cropping systems (increased crop growth, yield, soil health, economic returns, production sustainability), this research demonstrated the pitfalls of increased disease levels in potato early blight and the ineffectiveness of such a system in managing late blight, a potentially explosive foliar disease. Nevertheless, cropping systems and irrigation management provide useful insights into the sustainability of potato production systems.