The Potato Late Blight Risk Manager is using local weather and returning a risk rating from the previous 7 days. The previous 7 days are listed in colored boxes. Red days are high late blight risk, yellow are medium late blight risk days, and green are low late blight risk days. The total risk (based on 100% maximum) for the previous 7 days is presented in a white box on the screen. The risk of the previous individual days and the cumulated risk allow the user to make informed decisions on control of this important plant disease.
Few plant diseases can rival the widespread misery and despair produced by potato late blight. Potato late blight is caused by Phytophthora infestans, a fungus-like organism that over-seasons in infected tubers, cull piles, and in infected volunteer plants. The disease was noted in the U.S. in 1842, in Canada in 1844, and in Belgium during 1845. Three weeks of cool, foggy, rainy conditions in Ireland during 1845 helped create the late blight famine of 1845 to 1847 in which potato crops were decimated by the disease. Between 1845 and 1860, one million people died in Ireland alone as a direct consequence of famine, and one and one half million emigrated from Ireland. The “hungry forties” in England and other parts of Europe were also a result of potato late blight. Development of the lesions is favored by cool, moist weather. Nighttime temperatures in the 50s with daytime temperatures in the 70s, accompanied by rain, fog, or heavy dew, are ideal. Under Maine conditions, lesions appear on leaves in about 7 days after infection. Under ideal conditions, lesions have appeared in as little as 5 days after infection. It has been estimated that typical lesions produce up to 250,000 spores per day. This helps explain the rapid and devastating spread of the disease once it becomes established in a field. (from http://www.umaine.edu/umext/potatoprogram/Fact%20Sheets/Potato%20Late%20Blight.pdf)
Programmed By Eng. Ossama M. Mikhail