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Gardening Answers Knowledgebase

Plant Answer Line Question

Keywords: Sod webworms, Pesticides

Our maintenance contractor has told us that our grass is infested with the dreaded sod webworm, and that we should attack it immediately with the insecticide Covert. A little research tells me that this product is very toxic. Question: true or false? What are some commercially available alternatives if this is a toxic product?


It would be best if you could avoid using pesticides to control sod webworm. If you can encourage natural predators in your garden (such as ants, ground and rove beetles, parasitic wasps, and particularly birds), this should cut down on the infestation, whereas pesticides may well have a deleterious effect on beneficial insects and wildlife. University of California, Davis Integrated Pest Management also suggest that reducing thatch, and proper irrigation and fertilization of lawns will cut down on infestations of sod webworm.

Covert is a synthetic pyrethroid (as opposed to a natural pyrethrin). You may have already looked at the Material Safety Data Sheet for this product, but in case you have not seen it, here is a link. This document lists the product as highly toxic to bees, extremely toxic to fish and aquatic life, and notes that it contains ethyl benzene, a confirmed animal carcinogen. The Northwest Coalition for Alternatives to Pesticides also has information about the toxicity of permethrin (an ingredient of Covert). Here is more on permethrin and pyrethroid insecticides. Essentially, synthetic pyrethroids last longer in the environment than pyrethrins. They may be less toxic than some pesticides, but they are not without health and environmental concerns. Since there are nonchemical methods of control, it does not make sense to take a chance using something which is potentially harmful.

Bt or Bacillus thuringiensis is registered for use on sod webworm, and you can find it as well as beneficial insects, Steinernema nematodes from some gardening suppliers and well-stocked nurseries. Peaceful Valley Farm & Garden Supply has a large inventory of organic pest control products:

Organic Pest Control

Safer Caterpillar Attack

Parasitic Nematodes, Steinernema carpocapsae

Moth Egg Parasite - Trichogramma Wasp

I encourage you to pursue these alternatives to using the toxic product suggested by the maintenance contractor. Toxic chemicals can harm birds and beneficial insects, and using such products starts a vicious cycle, since those creatures would actually help keep down the undesirable webworm population.

Date 2017-04-14
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May 31 2018 13:14:08