It is sod webworm season again – I can tell by all the phone calls asking about the moths in the lawn. The lawn moths are harmless but sod webworms can kill a lawn but more likely, they damage random areas. So, what to do about sod webworms?
Sod webworm damage is circular in appearance, can be any size from a few inches to an entire lawn and often a distinct grey or tannish color. The most distinct symptom is the lawn is shorter in the damaged areas – this is because the sod webworms are cutting down the St Augustine grass.
Sod webworms feed on St Augustine grass leaves. However instead of eating the entire leaf, they chew across the leaf near the stem, let it fall and move on to the next leaf. This gives the area a “mowed” appearance. Then the leaf that has been cut turns grey to tannish brown giving the damaged area a distinct color.
If you look closely at the damaged area you will see the cut marks on leaves and stems where the sod webworm is feeding. Looking further into the canopy you’ll find the little green caterpillars curled up at the soil surface.
Sod Webworm Biology
The sod webworm is the larva of those little tan moths that rise up out of the lawn as you walk in the lawn. The moths are a nuisance but harmless and there is no effective control. The adult moths lay eggs in select areas of the lawn with the best chance for survival of eggs and larvae - concentrating eggs in select areas of the lawn.
The egg laying and hatching is constant – 24/7 - and the population can expand logarithmically in select areas of the lawn. A few sod webworms here and there are not a problem. However, when the sod webworm population explodes, they mow your select areas of the lawn for you.
No Need to Panic over Lawn Moths or Sod Webworms
No need to panic over the moths or sod webworms – a few sod webworms will do no harm. In areas where the population is high, they can damage the lawn, however St Augustine will fully recover from sod webworm damage if treated. Left untreated, the sod webworms will feed on stems and roots and destroy the lawn.
For the DIY
The best treatment is to spray the damaged area with an insecticide – just about any will do – and let the sod webworms feed on the treated grass overnight. Within a week the grass will return to a normal appearance. Treat as often as you see damage.
For My Customers
I have been treating for sod webworms since February – so no need to do anything. However, should you see any suspicious areas, feel free to call and I’ll check it out for free.