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Archive for Sunday, June 15, 2003

Maintaining tomatoes takes work

June 15, 2003

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Tomatoes are among the most popular vegetables in the home garden.

Unfortunately, they're known to have problems. With so many things that can go wrong, developing a line of defense can help ensure success later this season. So, if you have one or 100 tomatoes in the garden, here are some tips to help you harvest a lush crop of vine-ripe tomatoes.

The two most common problems on tomatoes are the fungal leaf spots -- Septoria leaf spot and early blight. 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 drops from the plant. They initially attack the lower, inner foliage then progress up the plant, killing more and more leaves. The plant may not die completely, but tomato production is greatly reduced. These two diseases are why many gardeners have tomato trees -- a 6-foot tall plant with a few leaves at the top -- not bushes, by the end of the season.

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 in the fall after harvest is a must.

This season, however, stake or cage plants to increase air movement and reduce conditions favorable for fungal infection. Be sure to clean tomato cages and stakes completely with a 10 percent bleach solution before using them this season. Next, spread straw mulch around the base of the plants to help prevent splashing water from spreading the disease. Likewise, 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 increases the chance of getting fungal infections. Next, 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 7 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 them at that point. Products that have Chlorothalonil as the active ingredient, such as Fertilome Liquid Fungicide and Ortho Garden Disease Control, PBI Gordon Multipurpose Fungicide work well.

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

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