Beware of the Tropical Sod Webworm

Moth that lay eggs that hatch into the larvae (worms) that feed on the lawn.

Larvae of tropial sod webworm feeding on graas.

Lawn damaged by tropical sod webworm.

Sightings of hundreds of moths over lawns have been a concern for area homeowners recently. These moths, although not a danger themselves, are laying eggs that will develop caterpillar offspring. The caterpillars are Tropical Sod Webworm. These caterpillars can ravage a lawn in short order.

Moths lay their eggs August through October. The moths are typically one half inch to three quarters of an inch long as adults and have snout like projections on their heads. The moth will lay eggs that hatch in seven to ten days. The larvae (caterpillar) can get to one inch long and are light green with dark spots on their body. The damage can be destructive and early detection is a big advantage.

To inspect for sod webworms look closely at the lawn for heavy chewing damage on the leaf blade of the grass. Evidence of caterpillar’s activity include chewing on the leaf edge, stripping grass clipping, and possibly green excrement pellets. Additionally, the worms leave trails of silky web, best spotted when dew is on the ground. Bird feeding in worm infested area can also be a sign.

Another way to see whether or not you have caterpillar is to use lemon scented soapy water. Mix, one ounce of lemon scented liquid soap per gallon of water. Pour the soapy water over the green grass right at the edge of the dying grass. The tropical web worm is easier to spot wiggling from the irritating lemon scented soap.

Lawns damaged can recover, however, the later in the season the damage happens, the less recovery you will see before winter dormancy. If the lawn was healthy before the larvae damage, the more likely it will recover.

If the sod webworm is detected consider using any of the listed insecticides:

  • Spinosad – an organic insecticide.
  • Bifenthrin – sold as Talstar, Ortho Home Defense and other brands.
  • Acephate – a systemic material, also Orthene and other brands.
  • Carbaryl – sold as Sevin.

All are effective and readily available. Follow the label directions on all pesticides.

The tropical webworm can be severe blow to our summer lawns. Early awareness and action can limit their activity.

8/15/2012 12:58:03 AM
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