Sod Webworm is not a common problem in lawns in the Edmonton area, but appears to becoming more of a problem as time progresses. Damage to turf is caused by the larval stage, while the adult moth is harmless. Early spring is when damage may first be observed and presents itself as small dead patches among the healthy green grass. Sod Webworms prefer sunny areas and can usually be found on south facing slopes where it is warm and dry. Generally, July and August is when the most severe damage occurs, as this is when it is hot and grass plants are not growing at their usual rates. More often then not, Webworm damage can be mistaken for summer drought stress. As the worms feed they cause thinning of the lawn. Weeds aggressively take advantage of this thinning and can become well established at this time.

One of the best ways to determine if you have Sod Webworm is to get down into the grass on your hands and knees and inspect these brown patches for Webworm activity. Pulling the turf up easily is one sign you may have Sod Webworm. Small green pellets are also a good indication. This is the waste product of the larvae. If you are unable to locate the larvae, try pouring about 4 litres of water mixed with 2 tablespoons of dish soap on the patch of dead grass. Generally within 5 minutes, if larvae are present, they will come to the surface. Twelve to sixteen larvae are a good indication of needing an application of insecticide.

The adult moth can usually be seen flying beginning in June and can be seen throughout the summer months. Once again the moths are harmless and do no damage to the lawn. Usually you see these moths flying up out of the grass as you mow the lawn, flying in a zigzag pattern. Observing the moths does not confirm damage is being or will be done by the larvae. These moths can fly quite a distance and may be coming from other infested areas. Drought stress or turf diseases can also cause thinning of turf. Any chemical control must also be focused on the larval stage, not the moths as the larvae are doing the damage.

Using the services of a certified pesticide applicator will ensure the safety of everyone involved.

For more information, call the professionals at Ace of Blades at 818-LAWN (818-5296),
or e-mail us at paul@aceofblades.ca.