St. Augustine Grass Sod and Webworms

Webworms

• Sod webworms overwinter as caterpillars in larvae located a few inches below the soil surface, according to the University of Rhode Island. In the spring during the time you have either just laid your St. Augustine sod or are about to install it, these pests pupate and emerge as moths. Moths lay their eggs within the St. Augustine grass, and the life cycle begins again. Gardeners may first notice signs of an infestation when they see moths flying above their St. Augustine grass. It takes only a week for the eggs to hatch and your grass to become damaged.

Damage

• Signs of webworm infestations begin as small yellow and brown spots appearing on grass blades. Areas of brown grass grow into small patches that are roughly 3 inches in diameter, according to Ohio State University. As the webworms grow in size and spread, their damage extends to larger areas of the lawn. It can be difficult to distinguish webworm damage from the injury caused by other pests such as fungal diseases. However, gardeners can conduct a webworm test to confirm their activity.

Test

• Kneel down and inspect the border between healthy green grass and dead grass. Part the grass with your fingers and look for green pellets, which are frass and indicate their presence, as recommended by Ohio State University. You can also conduct a drench test to find out the extent of their numbers. Mix 2 tbsp. of liquid dish soap with 2 gallons of water. Pour the mixture on one square yard of infested St. Augustine turf. Wait for webworms to emerge from the surface. If there are 10 or more, treat the area with a pesticide.

Treatment

• Wait for late spring to early summer to treat your St. Augustine lawn with pesticides. Webworm tunnels are too deep within the soil in early spring and fall for pesticides to make much of a difference, according to Ohio State University. Apply your pesticide in the late afternoon, so that it is ready for when sod webworms feed at night. Make sure that your St. Augustine turf receives three-quarters of an inch of water each week, so that it can bounce back from the damage.