08/21/2026
It is never too late to check your tomato and potato plants for late blight, especially during warm, wet late-summer weather! This fungus-like pathogen can cause significant yield loss if left unchecked.
The infection spreads by wind or through diseased plants. Because the spores need plant tissue to overwinter, the main sources of infection are contaminated, improperly disposed plant debris, volunteer plants growing from infected tubers, transplants, and compost piles. Look for dark-green or brown irregular
water-soaked spots on leaflets with the presence of white mycelium on or around the lesion on the leaflet underside. A light-green or yellow halo may also form around the lesions. Once an outbreak occurs, the pathogen can rapidly infect surrounding areas. The threat of late blight increases in cool, wet weather, in close plantings, or with overhead irrigation.
How to prevent this pathogen from affecting your harvest? Plant resistant varieties when starting your growing season, properly dispose of plant debris at the end of the season, rotate your crop away from nightshade family members, and frequently check for a late blight outbreak in your vegetable garden!
