Late Blight is a destructive disease which favors cool temperatures and high humidities for development. All parts of a plant can be effected. Grayish black lesions begin as water soaked spots and often have a foul odor. There may be a whitish mold on the underside of a leaf infected with late blight. Infected fruits have gray greasy spots which may later be covered by a white mold.
Late blight begins on infected volunteer plants or potato culls. When conditions are favorable, during moist weather inoculum is carried by the wind over considerable distances infecting other plants.
Late blight resistant/tolerant plants are being developed. A preventative spray program is recommended in areas prone to late blight infections. Some growers have taken to growing plants in hoop houses or high grow tunnels in an effort to keep foliage dry and prevent serious infect. Perimeter weeds may also play host to late blight and should be eliminated or sprayed if applicable. All infected foliage or fruit should be removed to prevent more inoculum the following year.
