Late Blight - Potato famine disease hits gardens and farms in the United States

Late Blight in Roma Tomatoes

The plant disease, late blight, which caused the Irish Potato Famine in the 1840’s and 50’s is hitting home gardens and threatening organic farms in the United States from Maine to Ohio. The fungal disease officially known as Phytophthora infestans causes large mold-ringed olive green or brown spots in plant leaves, and blackened stems. Late blight can quickly wipe out your hard work in your garden or farm.

While late blight is most famously known for the Irish Potato Famine, it also affects tomato plants. Seedlings from stores such as Walmart, Home Depot, Sears, Kmart and Lowes are some of the stores that have showed signs of the fungus.

Late Blight symptoms in potato leaf

This pathogen can move great distances in the air. The disease can spread rapidly in cooler, moister weather, infecting an entire field within days.

Meg McGrath, a plant pathologist at Cornell University’s extension center, said the risk is that many gardeners will not recognize the disease, putting commercial farms and especially organic growers at risk.

Commercial farms can use fungicides to control the blight, and while some sprays are approved for organic use, many organic farmers do not use them. The Cornell University Resource Guide for Organic Insect and Disease Management recommends drip irrigation rather than overhead in order to keep the foliage dry. ATTRA also has an article on Organic Alternative for Late Blight Control in Potatoes.

If your farm or garden is experiencing signs of late blight, contact your local county extension office to report your problem, and to learn how to control the issue.