- Worldwide distribution. On potato, tomato and relatives, and weeds. An important disease.
- Irregular patches of rot on leaves; white cottony growth with spores on undersides. Leaves yellow, shrivel and fall. Tubers rot. Spread in wind and rain and in “seed”.
- Cultural control: certified seed; remove volunteers; drainage; 2-3-year crop rotation; spacing to aid air movement; drip irrigation; limit amount of N; early tolerant varieties, avoid cull piles; collect and burn trash after harvest.
- Chemical control: chlorothalonil, mancozeb, or copper; alternate with, e.g., dimethomorth, metalaxyl, cymoxanil, or strobilurins. Phosphorus acid either alone or with chlorothalonil.
Pacific Pests, Pathogens, Weeds & Pesticides
Potato late blight (265)
Photo 2. Underside of potato leaf with spot caused by late blight, Phytophthora infestans. Note spores form on the margin of the spot.
Potato late blight
AUTHOR Grahame Jackson
Information from CABI (2015) Phytophthora infestans (Phytophthora blight) Crop Protection Compendium. (https://www.cabi.org/cpc/datasheet/40970); and information (and Diagram) from Schumann G, D’Arcy CJ (2000) Late blight of potato and tomato. The Plant Health Instructor. DOI: 10.1094/PHI-I-2000-0724-01. Updated 2005. Photo 2 Howard F. Schwartz, Colorado State University, Bugwood.org. Photo 3 Agriculture Research Service, United States Department of Agriculture.
Produced with support from the Australian Centre for International Agricultural Research under project PC/2010/090: Strengthening integrated crop management research in the Pacific Islands in support of sustainable intensification of high-value crop production, implemented by the University of Queensland and the Secretariat of the Pacific Community.