Although they are fairly easy to control, caterpillars like cutworms and armyworms can have a way of “sneaking” up on turf managers. For golf course superintendents, we’ve reached that point in the spring when black cutworms may be large enough to cause visible damage (»300 Degree Days). Unless you have a preventive program in place, keep an eye out for indications of damage. Black cutworm damage typically appears as small, irregularly depressed areas in tees and greens where the larger larvae have cut the grass down to the soil surface (Fig. 1)
On another note, increasing numbers of adult armyworms have been showing up in light traps around the State. These insects will lay their eggs on turfgrass leaves and stems. When they hatch, an army of hungry caterpillars will begin feeding and moving across the turf. The damage is difficult to notice at first, but as the larvae become larger (Fig. 2), they consume enormous amounts of green grass. Lawns can seemingly disappear overnight (Fig. 3). Areas that tend to be most vulnerable are those that are located next to agricultural fields, and ditches and roadways where tall grass and other vegetation is not mowed.
The following is a short list of recommended insecticides for caterpillar control (not meant to be all inclusive):
Bacillus thuringiensis Kurstaki (Small larvae only)
Beta-cyfluthrin
Bifenthrin
Chlorantraniliprole
Clothianidin
Deltamethrin
Lambda-cyhalothrin
Permethrin
Spinosad
Zeta-cypermethrin
Always read and follow label directions.
Figure 1. Black cutworm damage to a bentrgrass putting green surface. In this instance, cutworm larvae took up residence in openings caused by recent core aerification.
Figure 2. Late instar larva of the common armyworm flushed from tall fescue turf using a disclosing solution containing 1 tablespoon of lemon Joy® dishwashing detergent in 1 gallon of water. Notice the presence of several other larvae in the background.
Figure 3. Damage to a rural Indiana lawn caused by a heavy armyworm infestation. As long as water and fertility are available, the turf will eventually recover.