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Insect Control

Turf Pests

Lawn damage

What is damaging my lawn?

Occasionally, turf pests cause considerable damage to lawns. Winnipeg has two turf pests, the sod webworm and the glassy cutworm.

What does turf pest damage look like?

Brown or yellow spots expanding throughout the lawn. Birds, searching for turf pests, cause holes in the lawn.

How can I stop the damage?

Maintaining healthy grass helps lessen damage. Lack of water, poor aeration, thatch buildup and lack of fertilizer weakens turf. The turf becomes more susceptible to turf pest attack. Good fall monitoring can stop the feeding and damage.

How do I monitor for turf pests?

Cut off the ends of a coffee can. Select a site of green turf next to a dead area. Push the can into the green turf about 10 centimetres. Fill the can with a soapy water solution. Any turf insects pop to the surface when the solution soaks in.

How do I control turf pests?

Biological control options

Birds such as blue jays, sparrows, blackbirds and wrens feed on cutworms. By attracting these winged friends, natural control of the pest is possible. Place bird feeders close to infested areas. Skunks also dig and feed on cutworms. Beneficial nematodes also eat cutworms and other insects which are found in soil. Products containing these nematodes can be purchased at garden centers. Some parasitic wasps deposit eggs in the body of the cutworm which pupate on its back, killing the cutworm.

Chemical control

If physical and biological control measures are not effective, use a pesticide which will have a minimal impact on both you and the environment. Diatomaceous earth is an insecticidal dust which acts as an abrasive. It cuts the outer layer of the cutworm’s body causing it to dehydrate and then die. The dust should be sprinkled around the base of the plant so that the cutworm must cross it to access the plant.

Sod webworm

What do sod webworms look like?

Adult moths are 15 to 20 millimetres long and are beige to grey-white. The fully grown larvae reach 20 millimetres in length. The sod webworm larvae is pale in colour with a dark brown head.

How do sod webworms damage lawns?

Sod webworms feed on the grass blades at the crown above root level.

What is the sod webworm’s life cycle?

Adult moths deposit eggs over the turf in late July or August. The eggs hatch into larvae after a week. The larvae feed at night through the fall until the ground freezes and spend the winter in earthen cells. When the ground thaws in the spring, they begin to feed. In mid-July they pupate and emerge as adults.

Glassy cutworm

What do glassy cutworms look like?

glassy cutworm

Photo credit:
Joseph Berger under license CC BY 3.0

Adult moths are 25 millimetres long. They have dark brown to grey forewings and lighter coloured hind wings. Occasionally the forewings have a light spot. Mature larvae are 30 to 50 millimetres long. Larvae are robust with pale colouring and a dark brown head. When disturbed, cutworms curl up.

How do glassy cutworms damage lawns?

Cutworms severe the sod at the roots causing the sod to be easily lifted

What is the glassy cutworm's life cycle?

Females lay eggs on grass blades in late July or August. The eggs hatch into larvae in 3 to 10 days. The larvae feed through the fall until the ground freezes. They spend the winter in earthen cells. When the ground thaws in the spring, they begin to feed. In mid-July they pupate and emerge as adults.

Last update: July 22, 2020
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