Late Blight Management and Control
For more info: Rebecca Hargrave, 607.334.5841 x16 – firstname.lastname@example.org
Effectively growing Tomatoes & Potatoes requires understanding and responding to Late Blight Brochure - Added July 2012
August 30, 2011, Late Blight has been confirmed in Mount Upton, NY (Otsego County)
Begin to take precautions and properly dispose of infected plants.
Management and Control Options
Taken from http://ipmguidelines.org
Home Growers- cultural recommendations.
Use certified seed. Avoid wetting foliage if possible. Water late blight early in the day so aboveground plant parts will dry as quickly as possible. Avoid crowding plants; space apart to allow air circulation. Eliminate weeds around plants and garden area to improve air circulation. In autumn, rake and dispose of all fallen or diseased leaves and fruit or tubers. Locate new plants in a part of the garden different from previous year’s location. Resistant or moderately resistant varieties include Allegany, Elba, Rosa, and Sebago.
The fungus that causes late blight has recently become a major threat to home gardens and commercial growers because of the migration of new strains (genotypes) into the United States. The disease can readily spread from home gardens to commercial fields. Verification of a late blight diagnosis and implementation of prompt control measures are highly recommended. The newly arrived strains are more aggressive than previous strains. Cultural control measures such as those listed above may not adequately control these new strains. It is highly recommended that the use of protectant fungicides (mancozeb, chlorothalonil, or copper) be seriously considered.
Home Growers- chemical recommendations.
Follow disease sanitation practices* (see note). Use disease-free seed potatoes. If diagnosis is confirmed, use azoxystrobin (not near apples), Bacillus subtilis, chlorothalonil, copper soap (copper octanoate), or copper sulfate.
The fungus that causes late blight has become a major threat to home gardens and commercial growers because of the migration of new strains (genotypes) into the United States. Verification of a late blight diagnosis and implementation of prompt control measures are highly recommended. The newly arrived strains are more aggressive than previous strains. Protectant fungicides (chlorothalonil or copper products) should be used at first appearance of disease.
* Disease sanitation practices: Avoid wetting leaves when watering. Water early in the day so foliage will dry quickly. Avoid crowding; space plants to allow good air circulation. Eliminate nearby weeds, to improve air circulation. Remove any diseased or dropped leaves. At the end of the season, remove all plant tops, and dig up and remove roots.
If you think you have late blight this summer, please bring in a sample to Cornell Cooperative Extension as soon as you can for identification. Our offices are at 99 N Broad Street in Norwich.
In 2009 Late Blight, Phytophthora infestans, was a serious problem of tomatoes and potatoes all across the northeast. The weather conditions were perfect for disease spread, and when it was accidentally introduced, disaster struck. 2010 saw a lesser recurrence of Late Blight. Coming on later in the season, most likely from potato volunteers, pockets of tomatoes and potatoes were heavily affected.
Late Blight Facts:
- The organism that causes late blight cannot tolerate our cold winters, and does not survive from one year to the next on tomatoes in our climate.
- Late blight cannot survive on soil, only on living, fleshy plant tissue; even tomato seeds cannot carry the disease. But, overwintering, infected potatoes can.
Tips for 2011
- Only use CLEAN potato tubers for planting. If you have any question about your planting stock, throw it away.
- Consider planting Late Blight resistant tomato and potato varieties. They can still get the disease, but can often survive with it, or can fend it off until late in the season.
- Scout regularly for signs of Late Blight
- Preventative treatments are available
- If Late Blight occurs on your plants, destroy them immediately
- Collect tomato tops and all parts of potatoes in plastic bags and tie them shut. They dispose of them in the trash
- Burn affected plants
- Do not compost Late Blight affected plants. If it conditions are still acceptable, Late Blight can spread from half dead plants in your compost. And, potatoes can grow in your compost, harboring the disease overwinter.
Please do not to spray your soil with bleach, burn the soil, or dig it all up and replace it. You can even plant tomatoes in the same location if you like (although we recommend moving your crops to a new patch in your garden each year for the other diseases and insects that do overwinter).
If we encounter late blight again this year, you can spray with copper products or chlorothalonil. Last year, some gardeners brought in samples they thought had late blight but did not, so be aware of the other problems that tomatoes can have. Complete pesticide recommendations and cultural products can be found here: http://ipmguidelines.org/Home/.
Tom Zitter with the Department of Plant Pathology at Cornell University has composed three documents about tomato and potato late blight for growers and home gardeners. The full articles and the Late Blight Performance Table, with resistant varieties, can be found at the bottom of this article.
And, check the Long Island Horticulture and Research Center’s Late Blight Page at:
The disease that causes late blight has become a major threat to home gardens and commercial growers because of the migration of new strains (genotypes) into the United States. Verification of a late blight diagnosis and implementation of prompt control measures are highly recommended. The newly arrived strains are more aggressive than previous strains.
Current information about late blight and its management can be found at http://blogs.cornell.edu/lateblight/, check the right hand box for many great informational links.
Webinars on late blight for home organic gardens and organic farms can be found at http://www.extension.org/article/24989.
Details on submitting a sample to the Cornell Plant Disease Diagnostic Clinic can be found at http://plantclinic.cornell.edu/.
Call 607-334-5841 or e-mail email@example.com for more information.
Cornell Cooperative Extension enables people to improve their lives and communities through partnerships that put experience and research knowledge to work. Cooperative Extension is an equal opportunity program provider.
FOR MORE INFORMATION AND PHOTOS GO TO: http://blogs.cornell.edu/lateblight/
Planning Documents (released Spring 2010)
- Late Blight Info for Home Growers
- Late Blight Info for Commercial Tomato Growers
- Late Blight Info for Commercial Potato Growers
What to do with all those green tomatoes?
Try your hand at a couple of green tomato recipes- there is more than just fried green tomatoes.
Pickled Green Tomato Relish- http://www.uga.edu/nchfp/how/can_06/green_tomato_relish.html
Green Tomato Sauce for Pasta
2 1/2 pounds (about 6) green tomatoes, chopped coarse
1 large onion, chopped
1/4 c. olive oil
1 garlic clove, minced
1 bay leaf
1/2 tsp. sugar
1 tsp. salt
1 c. sour cream
In a food processor puree the tomatoes in batches. In a saucepan cook the onion in the oil over moderate heat, stirring, for 4 minutes. Add garlic and cook the mixture, stirring, for 1 minute. Add the tomato puree, bay leaf, sugar, salt and pepper to taste. Bring mixture to a boil and simmer it, stirring occasionally, for 30 minutes. Discard bay leaf, stir in sour cream, and serve over freshly cooked pasta. Makes about 6 cups of a rather piquant sauce.
Got more ideas- send them in to us!