Hot, humid days, cool nights foster tomato diseases

July 18, 2008 12:32 am

For those of you who didn't notice Tracey Peyton's column in last week's Norman Transcript, I'll cover the subject again: area problems with insects and diseases decimating many area tomato vines. First on my to do list is to clip off those leaves that are so diseased, spider-mite or aphid damaged that they no longer can carry on the job of photosynthesis, instead they act as a breeding source of mites and aphids that move up the vine to healthy leaves.
Also, hot, humid days and cool nights are the perfect formula for tomato diseases, our most common tomato diseases/conditions are: early blight, fusarium/verticillium wilt, tobacco mosaic virus, cat-facing, blossom drop and blossom end rot.
The best treatment for spider mites and aphids is to remove deeply damaged leaves from the garden. Place a water sprinkler or hose sprayer nozzle at the base of the plant or higher up if possible and turn the hose on full blast for a couple of minutes, that will wash many of the mites and aphids off the plant and give otherwise healthy vines time to outgrow and repair the damage. You won't be able to wash all the mites and aphids off in one treatment so repeat spraying the vines later in the day and the following as needed. This process has worked for me much better than using a commercial product against the tiny mites and aphids.
Early blight is a fungal disease that typically appears when days are hot and humid and nights are cool, stems and leaves turn brown with bottom leaves affected first, eventually drying up and falling off. With missing leaves, many fruit are exposed to sun-scald. Pieces of shade cloth pinned with clothes pins over the exposed fruit will prevent sun-scald. Mulch is the best preventative of fungal and viral diseases because they are soil-borne, infecting the plants when rain or watering splashes soil onto the plant.
There is no cure for fusarium/verticillium wilt. It shuts down the vascular system of the plant cutting off its food supply. Infected plants should be pulled up, tied tightly in plastic bags and placed with the garbage. The only defenses for these fungi are crop rotation of tomatoes and related crops such as eggplant and peppers. Buy plants that have some resistance or sterilize the soil through a process called solarization.
Tobacco mosaic virus comes from the hands of persons using or handling tobacco. It is a very serious problem that I once had; until I learned to bar people who smoke from going into the garden until they have thoroughly scrubbed their hands with soap.
Blossom-end rot gets its name from the water-soaked area surrounding a large black roughly circular leather scar where the blossom was attached. This condition is caused by a calcium deficiency usually caused by fluctuating moisture when the soil becomes very dry before a rain or watering system supplies the needed water and the cycle is repeated. Mulch plants and be consistent with watering, water vines slowly and thoroughly when the soil an inch down feels dry to the touch.
Leather-leaf is not a serious problem but a condition that sometimes comes about from hot weather or severe pruning which will usually correct itself with proper care. Radial cracking is another summer issue which frequently happens when fruit grows quickly during a period of rapidly changing weather conditions: rain followed by drought followed by another rainy period. During these times of drought, maintain consistent watering or try crack-resistant varieties such as Roma and Bragger varieties. The tomatoes don't look perfect but they taste just as good as those that don't crack.
You might ask yourself if growing your own tomatoes is worth all the effort. I'll tell you that most gardeners, including me, insist that when you have your first summer slice of juicy Cherokee Purple or Arkansas Traveler on a cheeseburger or topped with cottage cheese you'll forget all the care and sweat that went into its production -- at least for the moment.
Actually there is an alternative to the chore of growing your own tomatoes and still enjoy the delicious love apple: Buy from a local grower at the local Farmer's, Market, 603 E. Robinson St. at the Fairgrounds on Wednesday and Saturday mornings.
Betty Culpepper may be reached for questions, comments or ideas for future columns at bculpepper3@cox.net.

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