Tomato questions still coming

Published 12:00 am Sunday, June 6, 2010

Last week I mentioned some common problems facing tomatoes this year. This week the tomato calls continued and some more problems surfaced.

Q: How do I determine if my plants have early blight?

A: Early blight is usually not a problem this late in the season but we had two plants brought into the office this week with symptoms. As the name suggests early blight happens early in the plants lifespan. As the disease progresses, leaves turn yellow, wither and drop from plants. Tomato plants severely infected produce low yields of undersized fruit. First signs occur on the lower limbs and work their way up the plant. Since soil particles often contain the early blight fungus, it is a good idea to stake your tomatoes or mulch them to keep foliage from contacting the soil.

When detected, early blight is controllable with fungicidal application; chlorothalonil, maneb and mancozeb have been found to be effective in providing control when used early in the season. Other leaf diseases such as leaf mold, gray leaf spot and Septoria leaf spot are controlled by these fungicides. As an added plus, any of these fungicides may be “tank mixed” with an insecticide such as malathion or sevin, thus allowing a single application for control of disease and insects.

Q: What causes tomatoes to wilt?

A: There are five main causes of wilting in tomatoes. The first is water. Tomatoes can wilt from a lack of water or from an excess of water. Therefore be sure to water your tomatoes properly, one inch a week initially and then up to two inches at peak harvest, but make sure you use a good soil that drains well or raised beds.

The second a very common cause is bacterial wilt. This is common when you have a healthy plant one day then it looks dead and wilted overnight. Bacterial wilt can be diagnosed with a simple test. First, remove the plant from the soil. Cut a section from the lowest part of the stem, just above the roots, about four inches long. Have a jar of water ready so that the stem section can be suspended in the water, bottom end down. Then, watch the bottom end of the stem for a wispy, cloudy, milky ooze. This is bacterial streaming. The bacterial ooze is almost transparent, but can be seen releasing from the base of the stem. There is no cure for this soil borne disease except plant removal and crop rotation in future years.

A third common cause could be southern blight. This is very similar to bacterial wilt because it can cause plant loss overnight. It can be diagnosed by the white fungal growth at the soil line or by beige “seed pearl” sized balls of white, beige or brown. Plant removal is the only option at this point.

Two other problems could be Fusarium Wilt or Root Knot Nematodes. However both of these can be controlled by planting varieties that are resistant to both pest.

When possible try to rotate your vegetables every year and use varieties that are proven resistant to diseases and insects. If you are only growing a plant or two you may even consider using a pot on the back porch and some soil for the garden center to eliminate many of these problems.

David Carter is the director of the Adams County Extension Service. He can be reached at 601-445-8201.