Blight
From Wikipedia, the free encyclopedia
Blight refers to a specific symptom affecting plants in response to infection by a pathogenic organism.
It is simply a rapid and complete chlorosis, browning, then death of plant tissues such as leaves, branches, twigs, or floral organs.[1] 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 (Mont.) de Bary, the disease which led to the Great Irish Famine
* Southern corn leaf blight, caused by the fungus Cochliobolus heterostrophus (Drechs.) Drechs, anamorph Bipolaris maydis (Nisikado & Miyake) by the bacterium Erwinia amylovora (Burrill) Winslow et al., 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 (Uyeda & Ishiyama) Dowson.[2]
* Early blight of potato and
tomato, caused by species of the ubiquitous fungal genus Alternaria
On leaf tissue, symptoms of blight are the initial appearance of lesions which rapidly engulf surrounding tissue. However, leaf spot may, in advanced stages, expand to kill entire areas of leaf tissue and thus exhibit blight symptoms!!
Diseases and pests
Main article: List of tomato diseases
Tomato cultivars vary widely in their resistance to disease. Modern hybrids focus on improving disease resistance over the heirloom plants. One common tomato disease is tobacco mosaic virus, and for this reason smoking or use of tobacco products are discouraged around tomatoes, although there is some scientific debate over whether the virus could possibly survive being burned and converted into smoke.[3] Various forms of mildew and blight are also common tomato afflictions, which is why tomato cultivars are often marked with a combination of letters which refer to specific disease resistance. The most common letters are: V - verticillium wilt, F - fusarium wilt strain I, FF - fusarium wilt strain I & II, N - nematodes, T - tobacco mosaic virus, and A - alternaria.
Another particularly dreaded disease is curly top, carried by the beet leafhopper, which interrupts the lifecycle, ruining a nightshade plant as a crop. As the name implies, it has the symptom of making the top leaves of the plant wrinkle up and grow abnormally.
Some common tomato pests are cutworms, tomato hornworms and tobacco hornworms, aphids, cabbage loopers, whiteflies, tomato fruitworms, flea beetles, red spider mite, slugs,[4] and Colorado potato beetles.
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