Western lawn moth

The Western lawn moth (Tehama bonifatella) is a moth species belonging to the family Crambidae (grass moths). While their adult form is relatively harmless, their larvae, often categorized alongside other "sod webworms," are significant pests in turfgrass management. They are widely recognized in North American landscapes for their ability to compromise the aesthetics and health of managed turf.

The primary host plants for Tehama bonifatella include various species of cool-season and warm-season grasses used in lawns, golf courses, and athletic fields. The larvae feed on the grass leaves and stems, frequently cutting the plants off at the crown. This feeding behavior is particularly destructive because it prevents the grass from regenerating, leading to thinning and patchy lawns.

The biology of this species is characterized by complete metamorphosis. Larvae typically construct silk-lined burrows in the soil or in the thatch layer, which serves as a refuge during the day. As they grow, they enlarge these burrows, which are often accompanied by frass (larval waste) that looks like fine sawdust. Depending on local climates, they may complete multiple generations per year.

Damage symptoms usually appear as irregular, brownish patches of dead or dying grass that expand over time. In severe cases, the turf can be easily pulled away from the soil like a carpet because the root systems have been heavily compromised. The presence of these moths is often confirmed by observing small, light-colored moths flying erratically over the lawn at dusk.

Management and control strategies involve several integrated practices:

• Maintaining vigorous turf growth through proper irrigation and fertilization, which helps the grass tolerate light feeding.
• Reducing excessive thatch accumulation to limit suitable habitats for larval development.
• Applying systemic or contact insecticides when monitoring indicates high larval population levels.
• Utilizing biological control agents such as Steinernema feltiae (beneficial nematodes) which target the larvae within the soil profile.