2026 Late Blight Updates

Week of June 10

No reports of late blight have been made in the United States as of June 10, 2026.

Late Blight

Late blight is a destructive fungal-like organism, an oomycete, that affects potatoes, tomatoes, and certain solanaceous weeds. The organism does not typically overwinter in Pennsylvania due to our relatively cold winters, but may be able to survive in the center of a warm compost pile as long as there is living plant tissue present. Spores of the late blight pathogen, Phytophthora infestans, can be blown into Pennsylvania from other states or transported on infected plant material such as potato seed or transplants. Each year, Penn State Extension monitors late blight movement through usablight.org to help growers protect their potatoes and tomatoes. Late blight outbreaks for the 2026 growing season will be posted on this webpage.

Late blight symptoms can develop on leaves, stems, branches, and both green and ripe fruit. On leaves, pale green to brown spots appear on the upper surfaces. Leaf spot margins are often pale green or water-soaked. The spots may enlarge rapidly until entire leaflets are killed. In moist conditions, a fuzzy white sporulation usually develops near the margins of leaf spots on the undersides of leaves. When late blight infects petioles and stems, all foliage above the lesions rapidly becomes blighted and collapses. Lesions can expand rapidly, resulting in extensive, if not complete, defoliation within 14 days. Read "Late Blight in the Home Garden" to see photos and learn more about late blight disease cycle and development. 

Late Blight Management

Managing late blight effectively requires an integrated approach that combines resistant cultivars, vigilant scouting, cultural practices, and timely fungicide use. Preventing the introduction of disease through certified seed and healthy transplants is critical, as is diversifying plantings with resistant varieties. Regularly scouting your fields for the disease and checking Extension updates for nearby outbreaks can help you proactively manage late blight. Fungicides are most effective when applied preventively or at first symptom detection. Weather-based models can further optimize application timing. Cultural practices—such as improving air circulation, managing weeds and volunteer hosts, and removing infected plants—help limit disease spread, which can devastate fields within days under favorable conditions.

Organic systems rely primarily on protectant products such as copper, making proactive management essential. Refer to the 2026-27 Mid-Atlantic Commercial Vegetable Production Recommendations for a complete list of crop-specific fungicide recommendations.

 If you suspect late blight in your tomato or potato field, please contact your local Extension office or send a plant sample to the Penn State Plant Disease Clinic.  Since late blight can move quickly, prompt identification and reporting is crucial to allow growers to respond before the disease spreads.