Bad news: Late blight could be coming to your tomatoes

symptoms of late blight on tomatoes
Here are symptoms of late blight on tomatoes. If you think you have this disease on your tomatoes, please contact the Cornell Cooperative Extension Office in your county so they can take action. Photo courtesy Cornell Vegetable Program

Late blight was detected in Genesee, Cattaraugus and Allegany counties on Aug. 16, according to Cornell Cooperative Extension in Genesee and Chautauqua counties.

It could make its way to other parts of Western New York, too, because it can spread dozens of miles on storm fronts.

Late blight is a serious disease that can kill tomato and potato plants in just one week, according to Cornell Cooperative Extension in Chautauqua County. It’s best known for causing the Irish potato famine.

Since this disease is aggressive, spreads easily and can be very damaging to area farmers, Cornell Cooperative Extension asks that anyone suspecting they have late blight please contact their local Cooperative Extension office for assistance with identification.

Recognizing late blight

Late blight is caused by a fungus-like organism, according to Cornell Cooperative Extension in Genesee County.

Disease spots are often dark gray to brown in color and tend to be surrounded by pale green tissue. Initially, spot shape and size varies but eventually most of an infected leaf or stem will become discolored and die. Leaf spots often look slightly fuzzy on the underside of the leaf in the early morning or when the weather is wet and humid.

Late blight will put dark brown to black smears on tomato stems. Tomato fruit may also develop large, firm, greasy-looking, brown, gray or black smears on the upper part of the fruit.

Potato leaves show dark spots with fuzzy white spores on the underside during humid weather. Potato stems show similar lesions to those seen in tomato plants.

Don’t confuse late blight with the normal yellowing of leaves. The normal yellow leaves will have lots of small black specks, and the affected leaves will be mostly at the bottom of the plant. 

Dealing with late blight

See a factsheet here. It has information on what to do if your plants are affected by late blight. Here are fungicide recommendations for late blight.

If you think you have late blight, please make sure you contact the Cornell Cooperative Extension in your county so they can take action. What is just a disappointment to a home gardener can be devastating to area farmers.

5 Comments on “Bad news: Late blight could be coming to your tomatoes

  1. My tomatoes have just started to ripen. If I pick them totally green, before they get late blight, will they ripen in a bushel basket?

  2. Can this didease affect green bell peppers? I had one or two peppers that looked similar to the tomato picture but the brownish area was on the bottom of the peppers working its way up.

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