Late blight is a plant disease that mainly attacks potatoes and tomatoes, although it can sometimes be found on other crops, weeds and ornamentals in the same (Solanaceae) botanical family (New York State Integrated Pest Management Program). This disease is a water mold, and so is more of a problem in wet years than dry.
This is the disease that was responsible for the famous Irish potato famine! For Americans, late blight had also sometimes arrived like a plague and ruined crops, but a new fungicide introduced in the early 1970’s was very affective and managed to make this disease a rare one. However, new strains of the disease have since developed, and it has again become a problem for farmers in the United States (New York State Integrated Pest Management Program).
How Does It Spread?
There are a couple of ways that the disease can spread through crops. If an infected plant is introduced to your farm or garden, then it can infect others.
“Early in the season, the disease can be introduced into a field or garden on infected seed potatoes, from volunteer plants growing from diseased potatoes that were not harvested last season, from infected potatoes in cull piles (rejected potatoes), compost piles, or infected tomato transplants brought into the area.” (New York State Integrated Pest Management Program)
“Spores produced on infected potatoes and tomatoes can travel through the air, land on [uninfected] plants, and if the weather is sufficiently wet, cause new infections. Spores can also be washed through the soil to infect potato tubers, which may rot before harvest, or later in storage.” (New York State Integrated Pest Management Program)
Cornell University has released a fact sheet and a page of frequently asked questions detailing more information about the disease and how to treat or avoid it (the better alternative).
Know It When You See It
As a farmer or gardener, you must be able to recognize this disease and know how to control it! Regular inspections of growing crops is the most important step in the overall management of late blight.
It “is capable of wiping out not only your entire potato and tomato crop but also commercial fields very quickly under wet conditions, and farmers who grow potatoes or tomatoes are at serious risk of losing their entire income from these crops.” (New York State Integrated Pest Management Program)
Watch the following video to learn more about how to identify late blight in your garden!
Does late blight harm humans?
The answer seems to be no. There has never been any reported health risk or damage to humans associated with handling or eating infected plants.
“The unaffected parts probably are safe to eat. Tomato sections without blight symptoms likely do not pose a health risk to the consumer. They may not look appetizing and will have an off flavor.
However, no published scientific study on this specific issue was found to confirm this conclusion. On the other hand, there also have been no reports of a health problem possibly associated with consuming tomatoes or potatoes affected by late blight to warrant such a study.” (Cornell frequently asked late blight questions)
Keep an eye out for more information in a future post about treating late blight!
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