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Sod Webworms

CROPS IMPACTED: Bluegrasses and Bentgrasses

Sod Webworms

Family: Crambidae

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About Sod Webworms

Reproduction and Life Cycle

Several generations of sod webworms can appear each year. Larvae will overwinter in silk-lined burrows in the ground. Once spring comes, larvae will feed and begin their pupal stage of development later in May through to the beginning of June. Their cocoon is made up of soil, and plant and leaf fragments. They remain in their cocoon for approximately 10-14 days when they will emerge as a fully developed moth. At dusk the moths mate. The female will drop up to 200 white oval eggs onto the turf, which occurs through June and extends to the beginning of July. The eggs surface will turn brown as they age; this process takes 7-10 days. When the larvae hatch, they go through about 8 stages of development. They will continue to feed on the grass from July to August, and will then pupate.

Sod Webworm Identification and Habitat

Identification

Sod webworms are standard snout moths with antennas extending from their head. When this moth is at rest it has a narrow appearance, keeping its wings close to its body. The moth will fly short distances over the grass in a strange zigzag pattern when bothered. They typically hide in the shelter of a nearby plant during the day. Its wingspan is usually between 20 and 30mm wide. Sod webworms are either brown or a pale yellow-orange colour with a light gray lower half and its surface has dark brown scales. Its back wings are wider than the front ones, and are marked with stripes and sometimes spots. The larvae have a brown or sometimes black double row of spots on their back and are either creamy, pinkish, yellow, or light brown in colour with a dark head (usually brown or black). At night the larvae feed and when the sun comes out they hide away in burrows that are silk-lined. You can see the larvae move if the burrow is disturbed. During the pupal stage of development, sod webworms are about 12mm and are a light yellow. When it approaches maturity, it will turn brown.

Habitat

Sod Webworms often invade grassy areas throughout the United States and in southern areas of Canada. They tend to prefer areas that are hot and dry with small amounts of shade. They cause the most damage during the middle of the summer season; however, if there is more than one generation, they will feed on the grass during late fall or early spring as well. They will cause a grassy area to look spotty-brown, and the damage will continue to get worse throughout the season as the ground becomes drier and the grass grows slower. If your entire lawn turns brown, this is a sign that you have a bad infestation of sod webworms. This is why during droughts, infestations can go unnoticed.

Sod Webworm Management and Control Methods

Cultural Control

An effective method to control sod webworm infestations would be to use grass seed that is endophyte-enhanced. This is a fungus in the grass that helps resist insects. The fungus lives between the grass plants cell walls and produces alkaloids, which should successfully deter the sod webworms from feeding off of the grass. Please ensure to read and carefully follow all directions regarding the endophyte-enhanced grass as some can be harmful to livestock. For short-term care, you can fertilize and irrigate your grass to help it green-up. However, this will not rid the pest; it will simply mask the damage done. If you want long lasting results, the enhanced seed is the advised management method. There are also insect-parasitic nematodes to repress high sod webworm populations. With this method, it is also important to carefully follow all instructions; specific nematode species control specific pests.

Chemical Control

The chemicals used for sod webworms are often for controlling the larvae, as they cause the most damage. Application is done only when needed. It is always recommended to check for the approximate amount of webworms in the grass before applying the insecticide. Bacillus Thuringiensis is advised for use on young larvae. Application is most effective when it is done later in the afternoon or in early evening when the larvae come out of their burrows to feed. Carefully read the labels for cautions and proper application.

Latin / Alternative Sod Webworm Names

  • • Crambus
  • • Large Sod Webworm
  • • Greater Sod Webworm
  • • Lawn Moths

Sources

http://bugguide.net/node/view/56270

http://ento.psu.edu/extension/factsheets/sod-webworms-lawns

http://www.ipm.ucdavis.edu/PMG/r785301011.html

http://www.saferbrand.com/advice/insect-library/garden-insects/all-about-sod-webworms