July 22, 2010 at 8:34 a.m.
Tomatoes are part of the Nightshade family that include eighty-five genera and about 2800 species of plants, bushes, and trees. A few of the Nightshade family are poisonous but plants of the Solanaceae family that include garden vegetables, are not.
If you were careful in selecting your seed you know that there are early, mid-season, and late tomato varieties. I heard on the radio that some are picking Early Girl compared to the Big Boy that is one of the last varieties to ripen.
Another consideration some made was if they chose determinate or indeterminate varieties. Determinate tomato plants, also called bush, grow to a certain height and then stop. They also flower and set all their fruit within a relatively short period of time. This is an advantage if the tomatoes are being grown for canning purposes. Indeterminate tomatoes grow, flower, and set fruit over the entire growing season.
If you bought your seed by the packet or through a seed catalog, you noticed some letters on the description. The letter "V" indicates the variety is resistant to Verticillium wilt. The letter "F" stands for fusariumwilt and "N" stands for nematode resistance. Both Verticillium and fusarium cause wilting of the leaves and nematodes are microscopic worms that attack, and eventually destroy a tomato plant's root system.
Since we have received ample moisture followed by warm humid weather, we need to be aware of tomato diseases that follow these conditions. Tomato diseases are like other diseases in that the only way you can tell what the problem is by observing when it strikes and what part of the plant it attacks.
Septoria leaf spot is probably the most common disease of tomatoes. It begins to infect lower, older leaves about the time fruit sets. Newly infected leaves develop small brown spots on dead tissue. These spots often have light tan centers and dark margins. Often small, black pinhead like structures develop with the lesions. These reproductive structures, only visible with a hand lens, contain spots that are splashed by rain or overhead watering to healthy leaves. As the disease moves upward infected leaves turn yellow to brown. Severely infected leaves eventually fall from the plant, exposing developing fruit to excessive sunlight.
To manage Septoria leaf spot, keep the foliage off the ground and water early in the day at ground level. Mulch around plants to keep water from splashing and remove new infections as they appear. If you use preventative fungicides be sure it is labeled for control of Septoria leaf spot. Another article will cover other tomato problems.
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