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 to 27°C (50 to 81°F). The fungus grows most actively from 15 to 21°C (59 to 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 to 21°C (59 to 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 to 7 day fungicide schedule, using fungicides recommended specifically for late blight
Please visit website for more information – http://www.omafra.gov.on.ca/IPM/english/tomatoes/diseases-and-disorders/late-blight.html#advanced.
COMING EVENTS
Sept. 15 to 17 – Fergus Fall Fair (Fergus Agricultural Society). For more information, call Wendy Whittaker at 519-856-9621 or 519-843-2800 (fair weekend only), email info@fergusfallfair.ca or visit fergusfallfair.ca.
Sept. 15 to 17 – Harriston-Minto Fair (Harriston-Minto Agricultural Society). For more information, call Laverne Stinson at 519-338-5566, email info@harristonmintofair.ca or visit harristonmintofair.ca.
Sept. 19 to 23 – International Plowing Match and Rural Expo. For more information, call 519-767-2928, email admin@plowingmatch.org or visit plowingmatch.org.
Oct. 5 to 9 – Erin Fair (Erin Agricultural Society) For more information, call Eileen Brown at 519-833-2808.
