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