Late blight of potato/tomato was recently detected in Wayne County. To protect potatoes/tomatoes from late blight, residents should begin preventative measures. Late blight is a plant disease that mainly attacks potatoes and tomatoes, although it can sometimes be found on other crops, weeds and ornamentals in the same botanical family. Late blight is caused by a pathogen that survives from one season to the next in infected potato tubers. This organism is well known for its ability to produce millions of spores from infected plants under the wet weather conditions that favor the disease. Early in the season, the disease can be introduced into a field or garden on infected seed potatoes, from volunteer plants growing from diseased potatoes that were not harvested last season, from infected potatoes in rejected piles, compost piles, or infected tomato transplants brought into the area. Spores produced on infected potatoes and tomatoes can travel through the air, land on infected plants, and if the weather is sufficiently wet, cause new infections. Spores can also be washed through the soil to infect potato tubers, which may rot before harvest, or later in storage. Late blight used to be a frequent problem for potato farmers in the U.S., but a new fungicide introduced in the early 1970’s was extremely effective against late blight, and for many years it was found only rarely. Infected potatoes have shallow, brownish or purplish lesions on the surface of the tuber. The first appearance of lesions commonly occurs after periods of wet weather. Symptoms on tomato leaves and stems are similar to those on potato. To control late blight, gardeners must learn to recognize the disease symptoms and use an assortment of practices for disease management. Fungicide applications may be needed in some years to prevent loss of tomatoes and potatoes. If disease becomes severe it may be necessary to destroy infected plants to prevent spread to nearby gardens and farms. For more on Late Blight contact the Master Gardeners at 331-8415 Ext. 107.