Alert! Tomato and Potato Growers: Late Blight Found in Allegany County

Late blight is a highly destructive plant disease caused by the pathogen Phytophthora infestans, best known for causing the Irish potato famine. Late blight is caused by a fungus-like organism that spreads dozens of miles on storm fronts. This disease is notorious for its rapid spread and devastating impact on crops, particularly tomatoes and potatoes. Once it takes hold, late blight can destroy entire fields within days, leading to significant agricultural and economic losses. The disease thrives in cool, wet conditions, making it a constant threat during the growing season.

Disease spots are often dark gray to brown and tend to be surrounded by pale green tissue. Initially, spot shape and size vary, but most of an infected leaf or stem eventually becomes discolored and dies. 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 plant stems.

a) typical symptoms of late blight in tomato plants. (picture by Michael Mosgrove). b) P. infestans, the pathogen causing late blight (picture by Cristian Acosta).

Recently, late blight has been confirmed in Allegany County, New York. This is a serious concern for local farmers and gardeners, as it threatens tomato and potato crops throughout the region. The disease can spread quickly through spores carried by wind, rain, and even gardening tools, making swift action crucial to prevent widespread damage.

How to protect your crops?

To safeguard your crops and help prevent the spread of late blight, consider the following measures:

1. Choose disease-resistant varieties: When planting tomatoes and potatoes, opt for disease-resistant varieties. These types are bred to be less susceptible to late blight, reducing the risk of infection and crop loss.
2. Practice crop rotation: Rotate your crops to avoid planting tomatoes or potatoes in the same location for consecutive years. Crop rotation disrupts the life cycle of the late blight pathogen, reducing the chances of disease recurrence.
3. Apply preventive fungicides or biological control: Use preventive fungicides, whether organic or synthetic, to protect your crops from late blight. Also, you can consider applying biological controls like Trichoderma, a beneficial fungus that can help suppress phytopathogens in the soil. These measures can provide an extra layer of protection, especially in high-risk areas.
4. Report suspected blight: If you notice signs of late blight—such as dark, water-soaked lesions on leaves, stems, or fruit—report it to your local extension office immediately. Early detection and reporting are vital to controlling the spread of this disease.

Late blight is a serious threat to our tomato and potato plants, but with vigilance and proactive measures, we can help protect our crops. Stay informed, take preventive steps, and don't hesitate to seek assistance if you suspect late blight in your garden or farm. Allegany County residents may send pictures of the affected plants to Cristian Acosta at cfa34@cornell.edu or call at (585) 268-7644 ext 14. Commercial vegetable farmers should contact the Cornell Vegetable Program specialist directly. 

Last updated August 27, 2024