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Home TurfNotes Last week, I had a couple of inquiries from golf course superintendents wondering if it was too early for black cutworms to be showing up on golf greens. We have had some early captures of black cutworm adults that have arrived with some of the recent spring storm fronts, but it normally takes about 20 to 30 days for eggs to hatch and larvae to become large enough to cause visible damage.

The culprits are likely overwintered sod webworm larvae! We have about a half dozen common species of sod webworms in Ohio and all overwinter as partially mature larvae in silk-lined chambers about an inch deep in the soil underlying the turf. In mid-April, these larvae begin to construct their burrows to the turf surface where they will munch on turf leaves, just below the mow line. They continue to construct a short, slightly curved burrow across the soil surface which is also lined with silk and camouflaged with sand, soil and bits of grass clippings. These often show up as small brown streaks.

Fortunately, the burrows don't interfere with ball roll like the classic pock marks made by black cutworms and armyworms on greens. But, birds soon figure out that there can be a tasty caterpillar morsel somewhere within the burrow and they can really peck up a green in search of the food.

You can check to be sure what you are dealing with by using the soap disclosing flush. Simply use about two tablespoons of diswashing detergent (Joy, Ivory Clear, and Dawn Ultra have not caused turf damage) in two gallons of water. Spread this over a one-square-yard area and mark the corners (I use four golf tees to mark the area). If you have cutworms, they will pop up within a few minutes, but the sod webworm larvae are very slow, often taking 20 to 30 minutes, sometimes even more, to surface. So, come back later and closely inspect the soaped area to see if any of the tiny spotted caterpillars have surfaced.

In any case, if you need immediate relief, apply one of the pyrethroids and if the label allows, don't water it in after spraying. This will keep the insecticide residue on the leaf surfaces where it will be more likely eaten by the caterpillars at night.

As a compliment to this posting, a Sod Weborm enhanced podcast is available.
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Posted by David Shetlar