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Monitor Tomatoes For Top Fruit Yield
MISSISSIPPI STATE -- The time between when a tomato is placed in the well-prepared garden to when it yields delicious fruit can be full of danger for the plant from disease and insects.
Tomatoes require constant care to stay healthy and produce fruit. Check regularly for disease and insects and ensure plants have enough moisture and nutrients.
Dr. James Jarratt, entomologist with the Mississippi State University Extension Service, said the threat of cutworms is past for most gardeners as their tomatoes have been in the ground more than three weeks. Those who planted late should watch for plants cut off at ground level, a sure sign of cutworms. To protect the plants, spray or dust the rows with Sevin. A natural remedy is to put collars of aluminum foil around the base of the plants.
Aphids are tiny insects with a green to reddish tint found on the main stem of the tomato plant. They pierce the stalk and feed on the sap that contains the plant's nutrients.
"Very high numbers of aphids can build up and damage the plant," Jarratt said.
Treat by spraying with the appropriate solution of Malathion or Thiodan. A soap solution of 2 tablespoons of liquid dish detergent to 1 gallon of water has the same affect.
Jarratt said stink bugs are common, late season pests that damage the tomato fruit. A tomato punctured by a stink bug often ends up deformed with a white spot on the outside and a hard inner core. The only treatment for stink bugs is to spray with Thiodan.
Disease poses another threat to tomatoes' health. Dr. Frank Killebrew, Extension vegetable disease specialist, said gardeners across the state are fighting tomato spotted wilt.
"Spotted wilt causes the tops of the plants to blight and have a bunchy-type growth and the foliage to turn brown with black spots," Killebrew said.
Infected plants set few fruit, and those that appear often have yellow blotches on the surface and are not fit for consumption. Spotted wilt is a virus spread by thrips. These insects pick up the virus while feeding on weeds before moving to the more appetizing tomatoes. The disease appears 14 to 21 days after infection.
"By the time you control the thrips through insecticide applications, it's too late for the tomatoes," Killebrew said.
Tomatoes with this disease cannot be salvaged and should be removed and a new plant set, Killebrew said. The best prevention is to plant the tomatoes in a silvered mulch. The light reflecting off this repels some of the disease-spreading thrips, Killebrew said.
Early blight, a fungus, is the No. 1 tomato problem each year. There are no resistant varieties, so gardeners must pay close attention to spot the disease when it first appears. Early symptoms are brown spots on the lowest parts of the plants that turn the foliage yellow.
"It's very easy to spot the yellowed foliage. When you see it in a home garden, clip it off and get rid of it," Killebrew said. "That's the signal to intensify your spraying program."
Follow label directions and spray tomatoes with a broad spectrum fungicide each seven to 10 days after planting, even when plants appear healthy. Check with county Extension agents to confirm that the fungicide is approved for use on tomatoes.
"Don't get behind the early blight 8-ball," Killebrew said. "You're not going to get 100 percent disease control, but it will help you stay ahead of any problems. The key to good tomato production program is to control early blight. By regularly applying a broad spectrum fungicide, you will do a good job preventing septoria leaf spots and others as well."
Dr. David Nagel, Extension vegetable specialist, said once tomatoes are growing, the most important thing is to keep them well watered.
"Don't let them get too wet or too dry," Nagel said. "Either of these conditions will cause blossom end rot, identified by the black depression at the bottom of the fruit."
Tomatoes require 1 1/2 inches of water each week while they are setting fruit, and 1 inch before that. They prefer the moisture all at once, and mulch helps prevent the ground from drying out between waterings. Immediately water any tomatoes that wilt.
Nagel said slicing tomatoes require additional nitrogen when the first fruits are the size of a quarter. Add calcium nitrate or ammonium nitrate on the sides of the plant at a rate of about 1 ounce per plant. Well-decomposed manure or compost also works well when 1 cup per plant is added. Water immediately after fertilizing so the nutrients will be available to the plants.
Tomato pollen dies when temperatures exceed 93 degrees, but keep the plants well watered and continue the weekly fungicide sprays. Tomatoes will set fruit again when temperatures cool, Nagel said.