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Archive for Thursday, July 21, 2005

Anyone can grow top-rate tomatoes

July 21, 2005

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If you have ever planted vegetables, you know there is a fierce competition among gardeners. The keys to winning are tightly held secrets that many gardeners take to the grave. The prize: a fresh vine-ripe tomato by the middle of July.

However, there are several obstacles that hinder success this time of year. Here are some tips for turning your tomatoes into strong competitors and to help you become a winner:

Blossom end rot is the first of these hurdles. It is the brown leathery patch on the bottom or blossom end of the tomato fruit. It is not caused by a disease, and chemical sprays will not stop it. It is the result of a nutritional imbalance in the fruit - a calcium deficiency. Calcium is an important nutrient in the development of tomato fruit. Although there is usually an ample supply of calcium in garden soil, it is not always available for fruit development.

Warm spring temperatures cause rapid top growth with limited root growth. As the plant pulls calcium from the soil, it moves the nutrient in the water stream from roots to tops, bypassing the fruit and causing the deficiency. As the plant acclimates to summer weather, tops slow down and roots enlarge, bringing the plant back into balance. Available calcium can then be used for fruit development. Blossom end rot does not normally develop on later fruit.

The best way to stop blossom end rot is with water. Keep the soil uniformly moist throughout the growing season. Plants that have water are able to take up and move needed nutrients more easily. Next, do not overfertilize. Plants that are excessively lush because of over fertilization are usually more prone to developing blossom end rot. Slow, sustained growth is better than fast, forced growth. Finally, be patient. Although the first fruit to set does not develop normally and is not very appetizing, eventually the plant will work the problem out and you will harvest beautiful, full tomatoes.

There are two leaf diseases that need to be controlled, as well. Septoria leaf spot causes small, brown to black lesions, while early blight results in larger, target-shaped spots. Infected foliage turns bright yellow, then brown and eventually dies.

The diseases initially attack the lower, inner foliage, then progress up the plant, killing more leaves. The plant may not die completely, but tomato production is greatly reduced.

Leaf spots can be suppressed by a combination of cultural and chemical methods. Because both diseases overwinter on dead plant debris, a complete cleaning of the garden area is a must. Next, stake or cage plants to increase air movement and reduce conditions favorable for fungal infection. Third, use straw mulch around the base of the plants to help prevent splashing water from spreading the disease. Fourth, when watering, only wet the soil around the plant and try to keep the leaves dry. Wetting the leaves late in the day, coupled with dew formation at night, increases the number of hours the leaves remain wet and therefore the chance of getting fungal infections. Fifth, control weeds in the garden. Not only do they compete for moisture and nutrients, they crowd the tomatoes, increasing humidity and blocking air flow.

Finally, use fungicides. Applications every seven to 21 days will help slow or even stop the progression of these fungal diseases. Begin applications as soon as the first leaf spots are noticed. Do not wait until you see heavy leaf spotting because it is difficult to stop the disease at that point. Products containing Chlorothalonil as the active ingredient, such as Fertilome Liquid Fungicide and Ortho Liquid Fungicide, work well.

Other products to consider are Daconil, mancozeb, and copper-based products like Bordeaux. If rainfall washes the fungicide off, then reapply. As always, read and follow all the label directions.

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