Fabric protects tomatoes
Q.I saw tomato plants completely enclosed in a translucent fabric stretched over the tomato cage. Do you know why they would grow them in that way?
A. The fabric keeps white flies and thrips off the plants. These pests are very small sucking insects that can destroy blooms and reduce foliage effectiveness with their feeding. More importantly, they are notorious for their role in spreading diseases. The latest example of that problem was experienced in the fall of 2010 when white flies spread the Yellow Tomato Wilt virus to tomato plants all over the San Antonio area.
The problem with diseases is that these insects only need to penetrate the plant once to leave a virus. It doesn’t always matter if the insect dies immediately after that initial contact from any insecticide.
By using snap-type clothes pins and soil over the base of the fabric, the plant can be sealed within the covering. In addition to keeping disease-carrying insects out, the fabric reduces wind damage and provides some cold protection. The fabric lets in enough sunlight to maintain maximum growth rate.
The fabric is removed when the plant fills the cage. At that point, infection will not eliminate the crop.
Another way to prevent the disease from white flies and thrips on tomatoes is to use a resistant variety. Tycoon is resistant to the Yellow Wilt Tomato Virus.
Q.Is it necessary to spray fruit trees every week to produce blemish-free fruit? How about roses?
A. Fruit trees, especially peaches, and modern roses are vulnerable to insect pests. Insects, such as plum curculios and cucumber beetles plus several kinds of caterpillars and stink bugs, feast on foliage and fruit. For roses, in addition to thrips, expect chafer beetles, aphids, and caterpillars to infest them.
The best plan for fruit trees and modern roses is to spray every week with an insecticide and a fungicide. Rose growers should consider acephate and triforine. Organic rose growers can consider sulfur products, spinosad, and neem oil. For apples, plums, peaches, and pears, a combination of Sevin alternated with malathion and Captan works well.
You can mix your own combination spray or buy concentrates that already include both a fungicide and insecticide.
If you use an insecticide, check the label for the required time between spray and harvest. For crops such as blackberries, peaches, or tomatoes, that can be crucial. Carbaryl’s time between the last spray and harvest can be as short as three days or as long as two weeks, depending on the formulation and the crop.
Select a formulation that suits your situation and harvest all the ripe fruit before you spray.
Calvin Finch is a horticulturist and the San Antonio Water System’s project director of regional initiatives and special projects. Hear him on “Gardening South Texas” on KLUP 930 AM radio Saturdays noon to 2 p.m., and 1-3 p.m. Sundays. Or, e-mail him at firstname.lastname@example.org .