A weekly report prepared by the staff of the Ministry of Agriculture, Food and Rural Affairs (OMAFRA). If you require further information, regarding this report, call the Elora Resource Centre at 519-846-0941. Office hours: 8:30am to 4:30pm. For technical information, call the Agricultural Information Contact Centre at 1-877-424-1300 or visit the OMAFRA website: www.ontario.ca/omafra.
LATE BLIGHT
Scientific Name – Phytophthora infestans
Identification – Initial leaf symptoms are pale green to brown water-soaked spots, which enlarge rapidly and become brown to purplish-black. A pale yellow or green halo may surround the leaf lesions. On the underside of leaves, spots may develop a grey to white moldy growth, especially under conditions of high humidity. Brownish cankers may appear on leaf petioles and stems. These stem lesions may quickly girdle the stem and kill it. Under favourable conditions, the pathogen can blight the foliage so quickly, that it appears the plants were hit by frost. Lesions on fruit appear as firm greyish-green to brown, rough, irregular shaped blotches, which rapidly enlarge.
Often Confused With – Buckeye rot (Fruit symptoms are unlikely to be confused with other diseases, except buckeye rot; however, late blight causes the fruit surface to become rough.)
Biology – Spores are produced from 10- 27°C (50- 81°F). The fungus grows most actively from 15- 21°C (59- 70°F).
The disease may overwinter in plant debris or cull piles (potato or tomato). The organism can travel great distances by wind.
Period of Activity – The late blight fungus prefers temperatures from 15- 21°C (59- 70°F). Cool nights and warm days, with moist weather, are ideal for disease development.
Scouting Notes – Key diagnostic features on foliage are lesions that are not stopped at leaf veins. Symptomatic leaves can be sealed in a plastic bag with a damp paper towel overnight, then checked for a gray to white moldy growth on the underside. Fruit symptoms are unlikely to be confused with other diseases, except buckeye rot; however, late blight causes the fruit surface to become rough.
Thresholds – No tolerance. This disease is easily spread by wind and can rapidly destroy the crop.
Management Notes – Preventative fungicide sprays for early blight, Septoria and anthracnose protect against late blight. If the disease is present in the area, follow a 5- 7 day fungicide schedule, using fungicides recommended specifically for late blight
Visit omafra.gov.on.ca/IPM/english/tomatoes/diseases-and-disorders/late-blight.html#advanced for more information
COMING EVENTS
Sept. 9 to 10 – Aberfoyle Fair, for more information visit aberfoyleagricultural society.com.
Sept. 9 to 11 – Arthur Fair, for more information visitar thurfallfair.ca
Sept. 9 to 11 – Georgetown Fall Fair, for more information visit www.georgetown fallfair.ca.
Sept. 9 to 11 – Mildmay-Carrick Fall Fair, call 519-367-5821 for more information.
Sept. 11 – Paisley Fall Fair, more information at paisley fair.ca.
Sept. 13 to 14 – Wellesley Fair, more information at wellesleynehfallfair.ca.
Sept. 15 to 18 – New Hamburg Fall Fair, for more information visit newhamburgfallfair.ca.
Sept. 16 to 18 – Acton Fair, see website for more information actonfair.ca or call 519-853-4699.
Sept. 16 to 18 – Chatsworth, more information at chatsworthfallfair.ca.
Sept. 16-18 Fergus Fall Fair, for more information visit fergusfallfair.ca.
