Keep it Green, by Michael Womack
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Published
by the Corpus Christi Caller-Times. CLICK FOR NEWSPAPER DELIVERY
Saturday, July 28, 2001
Protect your plants from insects with herbicides
Insects such as saltmarsh caterpillars, whiteflies, and aphids have been on the rise in recent weeks.
Harvest time stirs up these critters, which then migrate to residential landscapes in search of food. The insect population is particularly high because their numbers have not decreased during the past few winters, which have been relatively mild.
Public enemy No. 1 very well might be the saltmarsh caterpillar. The insect is usually a problem on the edges of fields. They can be severe defoliators when present in large numbers, often migrating from one field to another in mass. Now that area cotton fields are no longer a viable food source, they are migrating to residential areas looking for more food.
Big eaters
CORRECTION:
Insecticides such as Sevin are the best alternative to killing caterpillars at the end of their feeding cycle.
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Saltmarsh caterpillars lay their eggs in patches on the undersides of plant leaves. Many insect egg are strategically placed on the bottom of leaves to protect both the egg and newly hatched, soft-bodied larvae from drying out in the sun.
New caterpillar hatchlings are voracious eaters. At this stage of their life cycle, their primary concern is feeding to increase their size. As they grow, they take on a "woolybear" appearance.
B.t. products such as Thuricide, Dipel and Bioworm are usually the recommended treatment. Unfortunately, the product has to be ingested and takes about two days to kill the caterpillars. Since these critters are nearing the end of their feeding cycle, a contact herbicide like Sevin may be a better alternative.
Sooty mold
Besides increasing caterpillar populations, whiteflies and aphids are also on the rise.
The telltale sign, even if you don't see the insect, is the presence of black sooty mold on the leaves of many common landscape and patio plants including hibiscus, crape myrtles, lantana and others.
Home gardeners often panic when they see the black sooty mold appear on their plants; however, it is important to remember that the mold is not the major problem. Insects including aphids, whiteflies, scale and mealybugs produce honeydew, a sugary substance, as they suck sap from your plants. The fungus is actually feeding on the honeydew, not your plant. However, light reception by plant leaves is greatly reduced by the mold.
What can be done about sooty mold? Unfortunately, there's not a lot you can do about the sooty mold itself. In small, isolated cases, it can be wiped from leaves of patio plants, but most people find that impractical. The real key is to identify the insects that are on the plant and then quickly removing them before populations increase.
New growth
Plants will eventually put out new growth free of the black sooty mold, as long as the insects are gone. In most cases your plant will be fine, you simply have to wait for the blackened leaves to naturally drop.
Be on the lookout for these potential problems in your lawn. Early monitoring followed by a spray program at the first sign of these insects will keep your landscape green and healthy. If you've already been hit with them, simply control the insects and wait for your plants to produce new growth.
Michael Womack is a horticulturist with the Texas Agricultural Extension Service. Got a question? Michael Womack will answer landscape and gardening questions. Call 886-4648, category 3025 to record your question. Write Keep It Green, Corpus Christi Caller-Times, P.O. Box 9136, Corpus Christi, TX 78469 or email wm-womack@tamu.edu
2000 Caller-Times Publishing
Company, a Scripps Howard newspaper. All
rights reserved.
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