Thursday, August 12, 2010

Tropical Sod Webworms

There are several pests that affect lawns in Florida. (Don’t we know it?) Here we will highlight a particular lawn caterpillar called tropical sod webworm (Herpetogramma phaeopteralis). Tropical sod webworm is an insect that undergoes complete metamorphosis. They have an egg stage, larval stage (several), pupal stage, and adult stage. The most damaging stage of the tropical sod webworm is the larval stage, which we all know as the caterpillar. A mature tropical sod webworm is about ¾”-1” long and is grayish-green in color. The more of your grass they have eaten- the greener they may appear.

Two tropical sod webworm caterpillars. The curled position at center is how you might find them resting during the day in your lawn.

Their turfgrasses of choice include St. Augustinegrass, bermudagrass, and zoysiagrass. They are most active in our area from spring through fall, but can be found year-round in South Florida. They feed on the grass blades and can cause a “ragged” appearance to the blades. If you have tropical sod webworm you may notice a thinning of leaf density and eventually brown patchy areas in the lawn. Tropical sod webworm larvae feed at night and can usually be found during the day coiled up at the soil surface. The presence of the moth (adult stage) is another sign of their existence. These moths lay their eggs on the grass blades and are active mainly from dusk until dawn. Click here for more information on tropical sod webworm and control methods.

The moth (adult stage) of the tropical sod webworm.

A properly maintained lawn can reduce the susceptibility of your turfgrass to these insects. Some of the practices that can strengthen your lawn include: proper mowing height for your turfgrass species, proper irrigation practices, and proper fertilization. Too much nitrogen can cause rapid leaf growth, which in turn increases your odds of caterpillar problems. Click here for more information on proper turfgrass maintenance.

Click here to watch an informative YouTube video on tropical sod webworms by Doug Caldwell, Ph.D., the Commercial Landscape Horticulture Extension Agent in Collier County, FL.

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