Microclimate and potential for late blight development in irrigated potato

Application of irrigation water can improve potato growth and tuber yield during periods of deficit rainfall. A variety of water application techniques exist; however, little is known of their relative impacts on potato late blight potential. The effects of sprinkler, sub-surface drip, and surface drip irrigation treatments on microclimate and potential for late blight development were evaluated on Russet Burbank potato over three growing seasons in central Maine. Leaf wetness, air temperature, relative humidity (RH), rainfall and soil temperature were recorded each year. The potential for late blight was assessed with a late blight simulation model. Leaf wetness and RH peaked during night hours, while canopy and soil temperatures were lowest during the same hours. Comparison of observed and simulated blight development revealed a good prediction of potato late blight by the simulation model. The onset of simulated blight severity and final predicted disease level differed among years. Slight differences in simulated disease levels were sometimes observed between irrigated and non-irrigated treatments; however, irrigation application method did not consistently impact microclimatic parameters associated with late blight development. These results indicate that microclimate conducive to late blight development was less impacted by irrigation treatments than by local macroclimatic conditions.