Larvae of three species of sod webworms reside in silk-lined burrows and emerge at night to feed on blades of grass, sometimes pulling them into their shelters to eat later. The larvae may leave large brownish or brown patches on lawns. Homeowners may use chemical, biological and cultural measures to control the Lucerne moth (Nomophila noctuella), the most southern lawn moth (Tehama bonifatella) and Sperry’s lawn moth (Crambus sperryellus).

Best Chemical Insecticides

Horticulturalists in the University of California-Davis (UC-Davis) urge insecticides containing the active ingredient spinosad as the very useful control of sod webworms, taking into consideration efficiency, effect on the environment and natural opponents. Implement these insecticides at speed indicated on the tag. Other chemical controls, ranked in order of efficacy, are those containing carbaryl — in California, these require permission from a county agriculture commissioner to purchase or use; insecticides containing azadirachtin applied in accordance with label rates; insecticides containing permethrin applied at the speed of 2/5 to 4/5 ounce per 1,000 square feet of lawn; and insecticides containing deltamethrin applied at the speed of 1/5 to 2/5 fluid ounce dissolved in a minimum of two gallons of water for each 1,000 square feet of lawn.

Best Biological Controls

The nematode Steinernema carpocapsae and BT (Bacillus thuringiensis ssp. Kurstaki nematode), a bacteria, rank third and second to the UC-Davis record of effective controls of sod webworms. Nematodes are minuscule round worms which live in the ground. S. carpocapsae is packed within an inert powder that is dissolved in water and sprayed on grass. Apply 25 million S. carpocapsae per 1,000 square feet of grass in warm, moist but not soggy dirt during the coolest time of day. A single-celled microorganism, BT lives in dirt and kills several species of moths. The two S. carpocapsae and BT are sold at many garden supply centres. Implement BT in accordance with the manufacturer’s instructions.

When to take care of

To find out if your turf requires chemical treatment, test the grass to see how many sod webworms are found. Combine 1 to 2 fluid ounces of dishwashing soap with 1 gallon of water and then use a sprinkling can to apply it evenly to 1 square yard of turf. Irritated sod webworms must surface in approximately ten minutes. Start looking for brownish or whitish moths up to 3/4 inch long or slender, grayish larvae up to 3/4 inch extended. If your lawn includes 15 larvae or moths a square yard, chemical or biological treatment is to be able.

Cultural Control

Bluegrass and bent grass are most susceptible to infection by sod webworms. Removing thatch will help destroy the webworm habitat. Damage brought on by feeding webworm larvae might not be noticeable in grass Vibrators over 2 1/2 ins high. Thatch and mow your lawn frequently to help avoid webworm infestations and keep it healthy in general.

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