Webworms:  A Common Minnesota Lawn Pest

Sod webworms are common lawn pests that belong to the family Crambidae. These small moth larvae are usually less than an inch long and have a straw-colored appearance. They are known for their destructive feeding habits on grass and can cause significant damage if left unchecked.

Web Worm

Sod webworms pose a threat to the health and appearance of lawns. The larvae feed on grass blades at the root, creating irregular patches of brown or thinning turf. Their feeding activity can result in weakened and sparse grass, making lawns more susceptible to drought, disease, and weed invasion. If a sod webworm infestation is severe, it can lead to the complete destruction of the grass, leaving behind bare patches.

Brown Patches

Sod webworms thrive in certain conditions that favor their development. They prefer warm and humid environments, and their populations tend to increase during the summer months. Overwatered lawns and excessive thatch buildup provide favorable conditions for these pests to establish themselves and multiply. Additionally, poor lawn maintenance practices, such as infrequent mowing or improper fertilization, can contribute to the susceptibility of the grass to sod webworm infestation.


Chemical treatment can be an effective way to manage sod webworms. Insecticides specifically designed for sod webworm control can be applied to the affected areas according to the product instructions. These chemicals target the larvae and help in reducing their population. It is important to carefully follow the recommended dosage and safety guidelines when using pesticides to ensure effectiveness and minimize potential harm to other organisms and the environment.

Grub B Gone

Alternatively, naturalistic or alternative methods can also be employed to combat sod webworms. One approach is to promote a healthy lawn through proper cultural practices. Regular mowing at the appropriate height and frequency can help deter sod webworms by reducing their preferred hiding spots.

Proper watering and fertilization based on the specific needs of the grass species can also help maintain a robust lawn that is less susceptible to infestations. Additionally, introducing beneficial nematodes or microbial insecticides that target sod webworm larvae can provide organic control options.

While sod webworms are considered pests due to the damage they cause to lawns, they do play a role in the ecosystem. As they feed on grass blades, they contribute to the decomposition process, releasing nutrients back into the soil. Additionally, sod webworms serve as a food source for various natural predators, helping maintain the balance of the ecosystem.

Natural predators, such as birds, spiders, ground beetles, and parasitic wasps, can help keep sod webworm populations in check. These predators feed on the larvae, reducing their numbers naturally. Encouraging a diverse and balanced ecosystem in the lawn can attract these beneficial organisms and provide a natural control mechanism for sod webworms.


To determine if sod webworms are present, inspect the lawn for signs of damage. Look for irregular patches of thinning or brown grass, especially in sunny areas. Additionally, you may notice small holes or burrows in the thatch layer, which are the entry points of the larvae.

Performing a gentle soap flush test, where a solution of soapy water is poured over a suspected area and observing for the presence of larvae coming to the surface, can help confirm their presence.

In conclusion, sod webworms are destructive pests that can cause significant damage to lawns. Their feeding activity weakens the grass and creates unsightly patches. Proper lawn maintenance practices, chemical treatments, and naturalistic approaches can be employed to manage infestations.

While sod webworms have negative impacts, they also serve as part of the ecosystem and are preyed upon by natural predators. Regular inspection and early detection are crucial for effective management strategies.