Blight

noun

1. a plant disease, typically one caused by fungi such as mildews, rusts, and smuts.

the vines suffered blight and disease

Blight is a rapid and complete chlorosis, browning, then death of plant tissues such as leaves, branches, twigs, or floral organs. Accordingly, many diseases that primarily exhibit this symptom are called blights. Several notable examples are

Late blight of potato, caused by the water mold Phytophthora infestans, the disease which led to the Great Irish Famine
Southern corn leaf blight, caused by the fungus Cochliobolus heterostrophus Drechs, anamorph Bipolaris maydis Shoemaker, incited a severe loss of corn in the United States in 1970.
Chestnut blight, caused by the fungus Cryphonectria parasitica (Murrill) Barr, has nearly completely eradicated mature American chestnuts in North America.
Citrus blight, caused by an unknown agent, infects all citrus scions.
Fire blight of pome fruits, caused by the bacterium Erwinia amylovora, is the most severe disease of pear and also is found in apple and raspberry, among others.
Bacterial leaf blight of rice, caused by the bacterium Xanthomonas oryzae (Dowson).
Bacterial seedling blight of rice (Oryza sativa), caused by pathogen Burkholderia plantarii
Early blight of potato and tomato, caused by species of the ubiquitous fungal genus Alternaria
Leaf blight of the grasses e.g. Ascochyta species and Alternaria triticina that causes blight in wheat
Bur oak blight, caused by the fungal pathogen Tubakia iowensis.
South American leaf blight, caused by the ascomycete Pseudocercospora ulei, also called Microcyclus ulei, ended the cultivation of the rubber tree (Hevea brasiliensis) in South America.

Symptoms

On leaf tissue, symptoms of blight are the initial appearance of lesions which rapidly engulf surrounding tissue. However, leaf spots may, in advanced stages, expand to kill entire areas of leaf tissue and thus exhibit blight symptoms.

Dissemination

Blight spreads by fungal spores that are carried by insects, wind, water and animals from infected plants, and then deposited on soil. The disease requires moisture to progress, so when dew or rain comes in contact with fungal spores in the soil, they reproduce. When it rains, water hits the ground, splashing soil and spores onto the lower leaves of plants, where the disease shows its earliest symptoms.

Blight on Tomatoes

When examining plants for blight, note symptoms carefully to identify the disease. While the treatment for all blight is the same, the symptoms are a little different.

While there is no cure for blight on plants or in the soil, there are some simple ways to control this disease.

Preventing Blight on Tomatoes

When planting tomatoes, make a plan to prevent blight. Incorporate these simple steps to keep your plants healthy.

Practice crop rotation by planting tomatoes in a section of the garden that has not been used to grow tomatoes or any other member of the Solanaceae family, such as eggplant, potatoes or peppers, in the last two years.
Read seed packages or plant labels carefully to select a tomato variety that is resistant to blight.6
Stake or cage tomato plants so that foliage grows vertically, off the ground.
Mulch well around plants.
When watering, use a soaker hose rather than an overhead sprinkler. This will reduce the amount of water on leaves and keep spores in the soil from splashing on plants.

Inspect the plants in your garden every few days for signs of damage. Fast diagnosis and a quick response are the keys to a healthy, tasty harvest.

Identifying Blight Types

Early Blight: Early blight symptoms usually begin after the first fruits appear on tomato plants, starting with a few small, brown lesions on the bottom leaves. As the lesions grow, they take the shape of target-like rings, with dry, dead plant tissue in the center. The surrounding plant tissue turns yellow, then brown before the leaves die and fall off the plant. While early blight does not directly affect fruits, the loss of protective foliage can cause damage to fruits due to direct sun exposure. That condition is known as sun scald.
Late Blight: 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, 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. Late blight does not overwinter in the soil because it requires live tissue to survive, but wind can carry spores up to 30 miles away from infected plants.

Treating Blight on Tomatoes

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.

Chesnut Blight Alert

Chestnut blight is a serious disease of chestnut trees caused by the fungus Cryphonectria parasitica. The fungus does little damage to host trees in its native range in Asia, but has devastated American chestnut when it was accidentally introduced to the USA more than 100 years ago via infected planting stock. The disease was introduced into Europe in the 1930s where it affects species such as the European or ‘sweet’ chestnut. It has since spread to most parts of the continent, causing serious damage in orchards and forests. Chestnut blight was detected for the first time in Britain in 2011 on planted imported trees, but is now considered eradicated. However, annual surveys and vigilance are needed to ensure that the UK remains free of the disease.