W e have been getting a lot of questions about vegetable gardens lately. If your garden is not doing so well, bring in a sample or perhaps the answers below may help.
Q: My tomatoes look horrible with leaf spots, distorted leaves and some leaves have only the main vein left.
A: The average tomato cannot tolerate Florida summers. The heat keeps the flowers from forming into fruit. Cherry tomatoes may survive the heat, and other cultivars are being developed but the cultivars you grew up north usually will not survive. Frequent rains will also cause fruit that does set to swell and crack, allowing rot to set in and ruin the fruit.
The high temperatures and humidity also cause tomatoes to get leaf diseases that cause spotting, browning and leaf drop. There is little you can do to prevent this without frequent fungicide applications. Leaving space between plants and training the vines to allow good air circulation will help the leaves to dry quickly when wet and discourage leaf diseases.
You can prune tomatoes to thin the number of branches and allow better air circulation but be sure you have an indeterminate cultivar. Indeterminate means it will keep growing taller and flowering/fruiting as long as conditions for growth are right. Determinate means that it will stop growing and flowering after a certain period. “Patio” cultivars are often determinate because they are selected to be small enough to fit easily on a patio.
Distorted leaves are probably caused by leaf miners. The larvae of these insects tunnel through the middle of the leaves, leaving whitish tunnel lines that cause the leaves to curl and be distorted. Because the insect is protected by the leaf, there are no contact insecticides that can be used and a systemic insecticide would not be safe on a food crop. There are beneficial insects that will kill the leaf miners, so it is best to encourage a diversity of insects in the vegetable garden.
If your tomato plant is looking like it only has stems left on it, you have a caterpillar eating the leaves. The tomato hornworm looks so much like a tomato stem that it is hard to find on the plant. When you start to see stems and no leaves you need to carefully check the whole plant and pick off and destroy any caterpillars before they eat all the leaves. An insecticide dust can be used, but it is most effective when the caterpillar is small. Always follow label directions.
Q: My sweet potatoes and beans have holes all through the leaves. How can I stop this?
A: There are many insects that eat holes in leaves. Plants can stand to have bits of the leaves removed and still thrive and produce a good crop. It may look unsightly to you, but the plant is still fine, and using too many pesticides to try and keep everything looking perfect may cause other unforeseen problems with beneficial insects. Unless the leaf canopy is seriously affected (greater than 50 percent), you are probably better off to live and let live.
Q: I bought some beautiful ornamental sweet potatoes. Will I still be able to eat the tubers?
A: The tubers on the ornamental sweet potatoes are edible, but they won’t taste very good. The plants have been selected for their good looks, not their good taste. When the plants die back in the winter, the tubers will remain unless dug out, and regrow in the spring, but may or may not be the same ornamental color.
Q: Clouds of small white moths fly up when I brush the foliage of my eggplants. What are they and are they a problem?
A: It sounds like whitefly. Whiteflies attack many plants. These pests will suck the sap from the plant, causing the plant to be less vigorous, but more importantly they transmit diseases. The adults resemble small whitish moths, and the immature insects look like clear greenish scales on the undersides of the leaves.
My favorite control in the vegetable garden is sticky yellow traps. The insects are attracted to yellow and the sticky coating catches them. You can purchase ready-made traps, or make your own with a yellow plastic picnic plate coated with Tanglefoot (a commercial brand of sticky goo) or sprayed with a thin coating of STP oil treatment. Keep it a thin coating — too much and it will run off.
Hang the traps at canopy level and within the leaf canopy to catch the whitefly as they fly around. You will need to change the traps frequently because they are not effective when covered.
Visit the Discovery Gardens and our plant clinic with your plant problems and questions from 9 a.m. to 4 p.m., weekdays, at the ag center, 1951 Woodlea Road, Tavares.
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