Home Gardening

Tomatoes battle several pests
The Coast Gardener Newspaper and Web Column - July 14, 2001

As promised last week, I will finish my discussion of diseases, environmental stress, and insects that often steal our crop of tomatoes. Wouldn't it be nice if the most popular vegetable for the home gardener was a little easier to grow?

Spotted wilt virus

This viral disease is carried by insects called thrips. New leaves at the tops of plants begin to curl downward, and dark purple streaks may appear on leaves, stems and fruit. Small dark spots may also be present on leaves. Unfortunately, no resistant varieties are available. This disease moves very rapidly. One should destroy affected plants to keep the disease from spreading.

Preventive measures must be taken to combat this disease. Thrips live in the weeds in and around the garden; therefore, it is important to keep the area clean. Shiny mulch placed around plants has been shown to reduce thrip populations by as much as 70 percent. Check with your favorite nursery or garden center for available products.

Environmental stress

Too much water can also cause your tomatoes serious problems. It is more common to see wilting of plants after very heavy rainfall or if your soil doesn't drain very well. Water logged soils do not hold enough oxygen for the roots to be able to work correctly.

If you have a plant in trouble that doesn't show readily observable symptoms, dig it up and observe the roots. Dark, sour smelling roots are often indicative of too much water. If water seeps into the hole after only a minute or two, too much water is likely the cause of the wilt. If the soil is waterlogged for only a day or two, tomato plants will usually recover.

Sunscald is another condition that seems to worsen as the season progresses. This condition results when excessive pruning or disease causes leaf drop and exposes fruit to the sun. Fruit quality is diminished when this occurs.

Too little water can certainly cause tomatoes to wilt. Mulching plants with pine straw or some other mulch helps conserve soil moisture and prevent blossom-end rot from affecting the fruit.

Stink Bugs

These insects worsen as the plants mature and the season progresses. These are sucking insects that have mouthparts that pierce the fruit leaving hard pimple-like knots all over the tomato. Stink bugs are usually brown or green shield-shaped insects. An endosulfan-containing insecticide (such as Thiodan) is the preferred treatment method.

Cutworms

These worms can be dull gray, brown, or black with stripes or spots. Cutworms feed at night or on cloudy days. They cause considerable damage to newly transplanted tomatoes by cutting the stem off at the soil line. It is a good idea to wrap a piece of newspaper around the stems of transplants when putting them in your garden or containers. Make sure the paper extends above the soil line for a couple of inches. Cutworms will not cut through this paper, thus keeping them from cutting down your tomatoes. The paper will rot as the plants mature.

Tomato Hornworms

The adult moth of a tomato hornworm feeds on the nectar of various plants, but the larvae causes extensive damage to tomatoes. The worm is green with diagonal white lines along its sides with a prominent "horn" at its tail. They are sometimes difficult to see, as they blend in easily with the leaves. Usually, you can simply pick them off the plants for control. Insecticides may be necessary if large numbers are present and hand picking them is impractical.

Tomatoes may be a lot of work, but just a few plants can provide fresh tomatoes all season long. Consider a fall planting this year. You will be the envy of your neighbors when you provide fresh tomatoes alongside the turkey and dressing on Thanksgiving Day.

These archived gardening columns were written by Chance McDavid, former Harrison County Extension Agent.