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DiseaseBacterial canker is a very serious tomato disease in commercial and home garden plantings in Kansas. It can cause lesions or cankers on any portion of the plant, including the fruit, or may result in a general wilt or decline of the plant. Diseased tomatoes first exhibit a yellowing and wilting of leaves on a portion of the plant. The leaves eventually become brittle and dry, and drop from the plant. Yellowish streaks may develop on leaf petioles, stems, and also internally in the water-conducting tissue of the main stem. In addition, small circular depressed areas called cankers may form on the stem. The most diagnostic feature of bacterial canker is the formation of fruit spots. These spots may be confused with those caused by bacterial speck or spot. However, fruit lesions caused by bacterial canker are bordered by a distinct white halo. These white halos may disappear as the fruit ripens.
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| Figure 1. Fruit symptoms of bacterial canker. |
CauseThe bacterium (Clavibacter michiganensis) can be introduced into fields on contaminated seed or on infected transplants. The bacterium also may survive in soil on infested plant material for at least one year. During the growing season, the small bacteria are dispersed by water (irrigation, rain) and infect plants through wounds or natural openings. Once inside the plant, the organism can invade the water-conducting tissue and be carried systemically throughout the plant. Disease development is favored by moderately high temperatures (80° F) and wet, humid conditions. ControlFollow a three-year rotation with non-solanaceous crops in commercial production. In home gardens, alter the planting location as much as possible. If you must replant in the same location, fall plow or till under dead plants to hasten decomposition. If bacterial canker was a problem the previous year, be sure to sanitize machinery, seedling and plant production materials including stakes, cages, seedling pots, etc. in 10% household bleach. Start transplants from seed that has been tested for bacterial canker contamination. Inspect transplants or young plantings for evidence of leaf spotting. Keep fields free of weeds by cultivation. Avoid the use of overhead irrigation. Instead, use drip tapes or lines, or soaker hoses for watering. Mulch around plants with plastic or straw. Avoid working with wet plants. Copper-based fungicides, including basic copper sulfate, copper hydroxide, and copper resinate, are generally not effective in suppressing bacterial canker. |
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Web updated 9/01/06 |