Late blight, the historic fungal disease responsible for the great Irish Potato Famine of the 1840s, has been found in Delaware and on the Eastern Shore of Virginia.

The disease largely affects tomatoes and potatoes and is favored by moist conditions, which the area has had an abundance of the past few days. Late blight presents a challenge to both homeowners and commercial growers, reports

According to the Irish Famine began quite mysteriously in September 1845 as leaves on potato plants suddenly turned black and curled, then rotted, seemingly the result of a fog that had wafted across the fields of Ireland. The cause was actually an airborne fungus (phytophthora infestans) originally transported in the holds of ships traveling from North America to England.

Winds from southern England carried the fungus to the countryside around Dublin. The blight spread throughout the fields as fungal spores settled on the leaves of healthy potato plants, multiplied and were carried in the millions by cool breezes to surrounding plants. Under ideal moist conditions, a single infected potato plant could infect thousands more in just a few days.

The attacked plants fermented while providing the nourishment the fungus needed to live, emitting a nauseous stench as they blackened and withered in front of the disbelieving eyes of Irish peasants. There had been crop failures in the past due to weather and other diseases, but this strange new failure was unlike anything ever seen. Potatoes dug out of the ground at first looked edible, but shriveled and rotted within days. The potatoes had been attacked by the same fungus that had destroyed the plant leaves above ground.

These days commercial potato and tomato growers are urged to make applications of materials specific for late blight. The most active choice for home gardens is a store-bought fungicide containing the active ingredient chlorothalonil.


How to spot Irish Famine disease

Why Famine came to Ireland

A plant hit with the late blight disease