Damage by black cutworm is to short-mown grasses through larval feeding.

Black Cutworm. Photo credit: John Capinera, University of Florida, Bugwood.org

Black Cutworm. Photo credit: John Capinera, University of Florida, Bugwood.org

Black cutworm, Agrotis ipsilon, is a common pest of short-mown bentgrasses found on golf course greens, approaches, fairways, and tee boxes across Pennsylvania.  Black cutworm is distributed throughout the continental United States but vary seasonally by latitude. This species cannot survive freezing conditions, and thus infestations originate from southern locations. The black cutworm can produce four to five generations in the southern-most states, three to four in the transition zone, and 2 to 3 generations in the northern parts of its range.

Damage in turf is through larval feeding; adults feed only on nectar. This insect is a well-known pest of corn, and will cut the stalks off at the base without consuming any of the plant. The larvae also feed on the turfgrass foliage.  Additionally, pruning the canopy near their burrow may cause depressions in the surface that disrupt ball roll on putting greens. These pockmarks become bigger and more irregular as the caterpillar continues to feed and are often mistaken for ball marks.

Identification

Adult

The black cutworm moth is a mottled brown to gray in color. There is a black dagger-shaped marking on the adult's wings. The wingspan of the forewing can range between 1.25- 2 inches (32-51mm).

Egg

The egg is creamy yellow in color. The eggs are smooth and have no other markings. Eggs are attached to the tip or the distal end of the grass blade.

Larvae

The black cutworm caterpillar's body appears green-gray to almost black, with a lighter gray underside and a broad stripe of lighter gray or brown down the middle of the back. The body can appear to be wet or slightly greasy. The body is hairless, excluding a few bristles. The head capsule is dark with a triangle-shaped marking. When full-grown, the larva is about 2 inches (50 mm) in length.

Monitoring

Black cutworm moths are nocturnal and can easily be monitored using a black light trap.  A black light trap uses a U/V light bulb mounted over a collection device, such as a bucket. Water and soap are added to the bucket, and the black cutworm adults fly to the light, and fall into the water where they can be collected and counted daily.

Black cutworm larvae are nocturnal feeders and generally reside in a burrow in the soil profile during the day. This behavior means a little extra effort is needed to find evidence of the caterpillar's presence before damage occurs. The presence of birds, especially the European starling, foraging on turf can indicate the presence of black cutworms. Birds will leave marks as they dig for cutworm pupae or larvae in the grass. Tufts of loose grass around probe markings can indicate where birds have pulled up larvae or pupa from the thatch or soil.

The easiest and most efficient monitoring technique for black cutworms is to apply a soapy water flush. Adding 1-2 fl oz of lemon-scented dish soap to 5 gallons of water will create a solution that can be applied to an area of turf. These will cause no damage to the turf and will work well in getting the larvae to the surface. In a matter of seconds to minutes after application, cutworms are irritated by the soap flush rise to the surface (largest to smallest) and can be collected and identified. The larvae stay on the surface until the sun dries them, after which they return to their holes. Soap flushing can also be performed after insecticide applications to assess efficacy. Turf should be well-irrigated after monitoring to avoid the potential for scald by the sun (phytotoxicity).

Management

Managing black cutworm below damaging thresholds can be achieved through a combination of cultural, biological, and chemical controls. Although observation of the migrating adults can help forecast a potential future problem, only management of the larvae will reduce damage.

Cultural Control

The challenge for turfgrass managers is in trying to balance the playability and aesthetic requirements of the turf. Sound cultural practices that include

  1. selection of turfgrass species and cultivars that are well adapted for a specific site or use and
  2. proper mowing, fertilization, irrigation, thatch management, and cultivation to promote healthy vigorous turf.

Healthy, quality turf is capable of tolerating and/or quickly recovering from insect feeding and is the very definition of “integrated pest management" (IPM).

Since the female moth attaches her eggs to the tip of individual blades of grass, mowing tees and greens every morning can remove most of the eggs that were laid the previous night. It is essential that the clippings be collected and disposed of at a distance (> 50 yards) from susceptible playing surfaces to avoid re-infestation as cutworm eggs survive mowing and can move substantial distances after hatching. Cutworm larvae also like to inhabit aerification holes, so filling these openings with sand or other top-dressing material soon after aerification may reduce their attractiveness to the larvae.

There are certain varieties of turfgrass that can play an important role in black cutworm management. These species can be more resistant to damage or can recover very quickly from damage. When complemented by proper mowing, irrigation, and fertilization, planting resistant varieties can reduce the need for chemical insecticides. Kentucky bluegrass, when planted in collars, aprons, and approaches surrounding more sensitive areas such as putting greens, can be resistant to black cutworm larvae Kentucky bluegrass may reduce the number of black cutworms that could potentially move onto these areas when they become larger and more mobile, helping to minimize damage.

The endophyte-enhanced cultivars of perennial ryegrass, tall fescue, and creeping red fescue provide some resistance to black cutworms. Endophytes are fungi that can be found in all parts of the plant; roots, stems, and leaves. Black cutworms that feed on endophytic varieties may develop slower or are deterred by feeding but are not killed by the alkaloids expressed by the endophytes.

Biological Control

Insect parasitic nematodes are microscopic round worms that can infest and kill black cutworm larvae. The insect parasitic nematode Steinernema carpocapsae is a good choice for use against black cutworms as they are surface-active or sit-and-wait “ambushers" that attack surface-mobile insects. When used properly, this nematode can provide control comparable to chemical insecticides. Insect-parasitic nematodes do not have a long shelf life. Likewise, be sure to follow all label directions regarding irrigating in this organism immediately following their application. If you rely on this nonchemical control method, then you need to remember that these nematodes are living, breathing organisms and should be handled with special care. Prior to application be sure to check the expiration date on each package of insect-parasitic nematodes. Applications should be made in the evening and irrigation should immediately follow. Nematodes can be applied along with most other turf protectants (e.g. insecticides, fungicides) using pressurized spray equipment, though screens should be removed from spray nozzles to avoid issues with clogging. Steinernema carpocapsae is available under the trade names Millennium® (BASF), NemAttack™ (Arbico Organics), and others.

Chemical Control

Curative

Using a curative approach is the most efficient strategy for achieving control of black cutworms using chemical insecticides. This strategy relies on the use of the monitoring techniques discussed above to identify black cutworm larval activity, followed by timely application of an effective insecticide. Black cutworm can be controlled with a wide variety of insecticides and the table below provides a list of insecticides recommended for black cutworm management. Black cutworm larvae are controlled by exposing them to the insecticides through both contact and ingestion. Applications are most effective when made in the late afternoon or evening, due to the black cutworm's nocturnal habits. When liquid materials are used, mowing and irrigation should be withheld for 24 hours to ensure that the insecticide remains in target zone for as long as possible. Granular materials should always be lightly irrigated (.1 inches) after application to release the active ingredient from the carrier.

Preventive

Due to their extended residual activities, some insecticide products may also provide protection against infestations for an extended period after application. When used at appropriate rates, products containing the active ingredients clothianidin, chlorantraniliprole, cyantraniliprole, or thiamethoxam may also be useful as part of a preventive strategy.

IRAC Code Class Active ingredient Trade Name
Preventive 28 Anthranilic diamides chlorantraniliprole Acelepryn
Preventive 4A Neonicotinoid clothianidin Arena
Curative 2B Pyrethroid bifenthrin Talstar
Curative 1A Organophosphate chorpyrifos Dursban
Curative 22 Oxadiazine indoxacarb Provaunt
Curative 5 Spinosad spinosin MatchPoint

Warning

The impact of several classes of insecticides on pollinating insects such as honey bees and native bees is a cause for concern. Because they are systemic chemicals absorbed into the plant, some of these products can be present in pollen and nectar, making them toxic to pollinators that feed on them.

Pesticides are poisonous. Read and follow directions and safety precautions on labels. Handle carefully and store in original labeled containers out of the reach of children, pets, and livestock. Dispose of empty containers right away, in a safe manner and place. Do not contaminate forage, streams, or ponds.