Control Webworms With Pyrethrin Insecticide
No natural insecticide products specifically attack sod webworms. However, several broad-spectrum insecticides are available that control webworms as well as other lawn insects.
A pyrethrin or pyrethrum based insecticide product is one of the least toxic of these products that works for webworms. However, it kills all insects, friend and foe alike, so it should be used as a last resort. Remember that excessive use of broad-spectrum insecticides risks sacrificing the natural protection provided by the predators and parasites that normally inhabit healthy turf grass, leaving your lawn open to pest attack in the next few months.
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Control Webworms With Neem Oil Soap
Minor sod webworm infestations are easily controlled by a drench of neem oil soap over injured lawn grass areas. Use about 2 tablespoons of soap concentrate with 1 gallon of water. Make sure you soak down through the thatch. The soap spray must contact the webworms or it will not be effective. Neem oil soap works by disrupting cell membranes in the insect’s body. It affects only immature stages and adults, but not the eggs. The soap drives the bugs out of the thatch, up into the grass blades, where they are vulnerable to attacks by predator birds or a yardener with a rake . When the webworms and moths crawl to the surface of the thatch layer, rake up the thatch along with the webworms and discard them in the trash or the compost pile. Read and follow the instructions on the product label. It costs roughly $5 to treat 1000 square feet of lawn with an insecticidal soap drench. Go to Yardener's Tool Shed for Neem Oil Soap Products
Control Webworms With Bt
In the caterpillar stage, sod webworms are vulnerable to insecticides only while they are still moving around and eating leaves and other plant parts. Spray the grass thoroughly with a product containing a beneficial bacteria, Bacillus_thuringiensis (Bt) two weeks after you first spot the sod webworm moths in your yard.
This should be the time the eggs hatch and young worms emerge. Bt works best when the caterpillars are actively feeding, which is sometime between April and June depending on where you live. The webworms eat the Bt as they feed. The bacteria poisons them with a toxin, and they stop eating and die within a few days.
For best results, mow the lawn before spraying with Bt. Delay mowing as long as possible after spraying so that the material will be picked up by each hatch of new caterpillars. To help the Bt stick to the grass and penetrate thatch, mix a surfactant or "spreader sticker" in the sprayer with the Bt. Because Bt washes off with rain, reapply it in 10 to 14 days to be sure you control the problem. Click here for more information in Yardener's Tool Shed about Bt Products and Choosing A Sprayer .
Control Webworms With Predatory Nematodes
You can also control webworms with beneficial predatory_nematodes . Because they are relatively expensive, they are most suitable for small areas under 1/4 acre. These microscopic worms are packaged as a powder or in a gel and are activated by adding water. Using a sprayer , apply the liquid slurry on infested grass in the late afternoon or early evening. The nematodes find their way to the webworms, burrow inside them, and reproduce.
They infect the webworms with bacteria, which kills the webworms within a few days. Nematodes can reduce a population of webworms by up to 80% within several weeks. Because the nematodes travel on a thin film of water through the turf, it is important to soak the lawn with 1/2 inch of water before applying them and again afterward. Read the package label carefully and follow the instructions. It costs roughly $20 to treat 2500 square feet of lawn with predatory nematodes. Click here for more information in Yardener's Tool Shed about Buying Predatory Nematodes or Choosing A Sprayer