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Caterpillars put the bite on yard shrubbery

Posted: August 18, 2013 - 12:02am  |  Updated: August 18, 2013 - 8:35am

With every season, there are different pest problems. There are two major pests in this area whose work will be noticed in a few weeks. It is the time of year when we start seeing fall armyworms and redheaded azalea caterpillars.

Fall armyworms (Spodoptera frugiperda) are a tropical caterpillar species that survives in warmer climates along the Gulf Coast and South Florida. They are worms in name only.

They start infesting plants in South Florida in February and March and move north as the weather warms. They tend to show up in our area in mid to late August or the first week of September, and they can last until frost. Armyworms are seen every year, but they do tend to have a cyclic pattern of every three years for a major outbreak.

Unfortunately, the last time a major outbreak hit Columbia County was three years ago. In our area, fall armyworms are major pests to Bermuda grass, millet and fall vegetables. Many people report damage to home lawns, hay fields and pastures.

Armyworms get their name from the large number of caterpillars that can be in an area, like an army. The adult stage is an ash-gray moth with a wing span of about 1½ inches.

The female moth will lay about 400 eggs. These eggs are laid at night on fence rails, tree trunks, and the underside of plants.The eggs hatch within two to four days. When the caterpillars are small, they will chew on the underside of the leaf without consuming the entire leaf. As the caterpillars get larger, their consumption increases, and a major infestation can consume an entire lawn in one night.

When the food source becomes scarce, the entire population of caterpillars will move to a new food source. Not every caterpillar found in the landscape this time of year is a fall army worm. A member of the “army” can be identified by the upside down “Y” on its head.

If a spot in the lawn appears to be losing foliage, look for armyworms. In bright sunlight, armyworms will be found near the soil surface. Use a soap flush to help find the caterpillars.

To make a soap flush, mix three to five gallons of water with two tablespoons of dishwashing liquid. Sudsy water is not desirable because it will mask the catepillars. Therefore, fill the container first with water and then add the soap. Pour the mixture over a 3-foot-by-3-foot area. If there are caterpillars or other insects in the turfgrass, they will emerge.

If armyworms are found, they can be treated with Bacillus thuringiensis (Bt, Dipel), carbaryl (Sevin) or various pyrethroids found in the garden centers. Two generations of armyworms can infest an area going into fall. Remember, they can continue to be a pest until the first frost.

The other pest that causes problems is the redheaded azalea caterpillar. This is a serious defoliator of azaleas. The damage to the azaleas can occur seemingly overnight and the plants completely stripped of foliage. The redheaded azalea caterpillar are easily identified by their red head and legs with yellow or black bodies. The female moth, as in the case of armyworms, lays a large number of eggs in a cluster. Therefore, there are a large number of caterpillars on one shrub.

To control these caterpillars, the azaleas can be treated with the same products used to control armyworms. Acephate (Orthene) also can be used, but the temperature must be 80 degrees or lower before using this product.

The best defense is to have a proactive scouting offense. Scout the landscape plants and turf for these pests now and use the soap flush on turf to find small caterpillars. Treat only after caterpillars are identified and be sure to follow the instructions on the pesticide.

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