Back Issue
July/August 2001

Tomato Troubles
by John J. Leto

By this time in the growing season, strange things begin to happen in the tomato patch. Those perfect little tomato seedlings have grown from cute little wonders of nature into 3 foot or taller unruly monsters. Now, before harvest, is the worst time for tomato troubles.

Caring for Tomato Plants
How you care for your tomatoes during the summer can help to minimize potential problems.

Your tomatoes need an even supply of moisture throughout the growing season. Applying a heavy mulch to the surface of the soil, after the soil has warmed up, will help to maintain a consistent level of moisture in the soil. Fluctuating moisture levels can result in misshapen fruit, and contribute to blossom-end rot and growth cracks.

The best irrigation for tomatoes is a slow, deep watering, which encourages the plant to grow deep roots. Use soaker hoses or drip irrigation to deliver water directly to the roots without wetting the foliage. Wet foliage supports the growth of fungi that can attack the fruit and plant. Do not water late in the day because the foliage does not have a chance to dry off before nightfall.

Wait until the fruit is golf-ball sized before applying any fertilizer, then side dress each plant with 2 to 4 ounces of 5-10-5, keeping it away from the foliage and fruit. Cultivate lightly and water deeply. Repeat this procedure every 3-4 weeks throughout the growing season.

If you are a smoker, wash your hands thoroughly with soap and water before handling your tomato plants. Tobacco mosaic virus is readily transmitted from plant to plant by your hands.

Tomato Diseases
According to Dr. Victoria Smith, an assistant scientist at the Connecticut Agricultural Experiment Station, the most common tomato diseases in Connecticut are early blight and Septoria leaf spot. Anthracnose can occur in a wet, windy summer when a tropical storm or hurricane blows through. But it is usually not a problem.

Both early blight and Septoria leaf spot are caused by fungi which attack the leaves, rendering them quite unsightly. “It’s not worth spraying a home garden to control them,” says Smith. “By the time these diseases appear in mid-July, most tomato plants have set their fruit and established their yield.” The best control is to remove all suspect leaves and fruit and discard them in the household trash; do not add them to the compost pile because these fungi can overwinter in plant debris.

Early Blight
Early blight often occurs during the first assault of hot and humid weather. Look on the oldest leaves for dark brown spots, 1/4 to 1/2 inch in diameter, with dark concentric rings. Eventually the leaves turn yellow and fall off, usually from the ground up. Fruits may be infected.

Septoria Leaf Spot
Septoria leaf spot does not usually damage seedlings, transplants, or fruit. Symptoms usually first appear on the older, lower leaves and stems when fruits are setting. Look for small, water-soaked circular spots 1/6 to 1/8 inch in diameter on the undersides of older leaves. The spots are distinctively circular and are often quite numerous. As the spots age, they sometimes enlarge and often coalesce. When spots are numerous, affected leaves turn yellow and eventually shrivel up, brown, and drop off. Defoliation can quickly spread up the plant towards the new growth.

Tomato Insects
I control pests by encouraging praying mantises, predatory wasps and toads, all of which consume an astounding number of insects without upsetting the delicate balance of nature.

Earlier in the year, cutworms and flea beetles do the most damage to young tomato plants. By the time summer comes, the most common bad-guy bugs are aphids, white flies and tomato hornworms.

Spraying with insecticidal soap will control aphids and white fly nymphs. “Spray first thing in the morning after the plant’s been well watered,” says Edmond Marrotte, consumer horticulturist for UConn’s Cooperative Extension System. “This will minimize burning to the foliage.” Be sure to spray the plant thoroughly, including the undersides of the leaves where the white fly nymphs are feeding.

Aphids
Aphids are the most numerous and easiest to spot insect in my garden. Look on the undersides of leaves and on the tender terminal growth for these small green or pink insects. Their feeding can cause curling of the foliage. They are carriers of several virus diseases. They suck out plant juices and excrete honey dew which attracts ants. Fortunately they are easily controlled with a spray of water from the hose or insecticidal soap.

Whitefly
This is a true pest from hell! Look on the undersides of leaves for these miniature white moth-like insects that fly off in a cloud when they are disturbed. Several life stages of this insect can be present at the same time — egg, crawler, nymph, adult. The easiest stage to control is the nymph.

Yellow sticky boards are an alternative to spray. The color attracts the insect and the sticky causes them to adhere to the board. Be sure to clean traps frequently; it’s amazing how quickly insect numbers mount up.

Tomato Hornworms
Tomato hornworms are the most dramatic of the tomato insects. They are 3 to 4 inches long with a horn at the tail end. Handpicking is the best method of control, however, let them be if you see white oval projections attached to their skin. These are the pupae of parasitic wasps that have been eating the caterpillar from the inside out.

“Tomato hornworms are very small (less than 3/8 inch) when they first hatch,” says Ed Marrotte. “The larvae begin eating right away and they will grow quickly; an easy way to find them is to look for their droppings.” Then, pick them off.

Follow a set pattern to control insects and disease and practice good sanitation by removing all dead leaves and weeds from your garden. Who knows, you may end up with the best of all tomato problems: How to enjoy your abundant harvest!

John J. Leto lives in West Haven and has been a volunteer at the Beardsley Zoo Greenhouse in Bridgeport for 12 years. He is the President of The Greater Bridgeport Men’s Garden Club and Tunxis Hill Garden Club of Fairfield. He is a frequent guest on WICC 600 AM radio shows including “Italian House Party” and “Family Breakfast Show”.

Connecticut Gardener
P.O. Box 248
Greens Farms, CT 06436
1-800-600-0476
email: editor@ conngardener.com