Late blight can affect tomato plants at any point in the growing season and at any stage of growth. Symptoms appears at the edge of tomato leaves, with dark, damaged plant tissue that spreads through the leaves toward the stem.
White mildew may grow on the lower leaf surface of the affected area. This type of blight progresses rapidly through plants in humid conditions, 3 and if left untreated, can spread to fruits. Septoria Leaf Spot. Like early blight, the first symptoms of septoria leaf spot often begin on the lowest leaves of plants after fruits appear.
Rather than showing as a few lesions per leaf, septoria leaf spot appears as many tiny, brown spots on leaves. Lesions continue to grow and spread before causing leaves to fall off. This type of blight does not usually affect fruits. Early blight and septoria leaf spot spores survive the winter in the ground, causing the disease to return next year. Once blight is positively identified, act quickly to prevent it from spreading.
Remove all affected leaves and burn them or place them in the garbage. Mulch around the base of the plant with straw, wood chips or other natural mulch to prevent fungal spores in the soil from splashing on the plant. When planting tomatoes, make a plan to prevent blight.
Because they are relatively easy to grow, tomato plants are common in many gardens. Tomato plants tend to have a good number of branches, can spread between 24 and 72 inches and tend to trail when they produce their bounteous fruit, though some varieties are known to grow upward instead.
Their leaves carry a strong odor and many hairs, and they can reach around 18 inches in length. Their yellow, five-petaled flowers can grow to 0. According to the Missouri Botanical Garden, there are many diseases that can afflict tomato plants and their fruit, but few of them actually make the fruit itself poisonous to eat.
The two forms of blight that tomatoes regularly see — early blight and late blight — will not entirely ruin the fruit, though they tend to look gross. Afflicted spots can be cut off, saving the rest of the fruit for culinary uses. Identifying the two types of blight with which tomato plants can be infected is also quite easy. According to the University of Minnesota Extension, early blight is often caused by two related fungi, Alternaria tomatophila and Alternaria solani. On foliage, this disease will often appear as dark spots on older foliage that hangs near the ground, which can sometimes develop yellow concentric rings.
Citric acid is less widely available, but is used mainly by large commercial canneries. Other acids such as ascorbic acid vitamin C; Fruit Fresh or acetic acid vinegar are not recommended. According to the USDA, diseased tomatoes, or those that are frost-damaged or harvested from dead vines may not develop the proper level of acidity for safe home canning.
And what about potatoes? Potatoes showing signs of late blight infection should not be used for home canning. Discard the whole potato rather than cutting off diseased portions since the fungus may spread to the interior. Since potatoes are a low-acid food, they should be pressure processed. We teach, learn, lead and serve, connecting people with the University of Wisconsin, and engaging with them in transforming lives and communities.
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