Common names:Black or greasy cutworm, variegated cutworm. There are many species of cutworm with various common names.
Latin names: Various Agrotis spp., including Agrotis ipsilon (Black cutworm), Agrotis longidentifera (Brown Cutworm), Agrotis segetum (Common Cutworm) and Agrotis subalba (Grey Cutworm). Also Peridroma saucia, Chorizagrotis auxiliaries amongst other species.

Life cycle and description

• Adult stage: Dark gray, black or brown colored moth with markings on the front wings, wingspan of 40 to 50mm, length 20 to 30mm. Females are darker than males and begin egg laying 5 to 11 days after emergence. Adults are nocturnal and lay eggs on vegetation, on moist ground around plants, or in cracks in the ground. During the daytime, adults hide in vegetation.
• Egg stage:Pearly white, round, diameter of 0.5mm. Eggs are laid singularly or in clusters. Eggs can be laid in clusters of up to 2000, but generally are laid in clusters of a few hundred. Eggs hatch during the 3 to 11 day stage, depending on temperature.
• Larvae stage: Larvae are greasy in appearance and can range in color from gray to brown or black depending on species. Larvae generally have two spotted yellow stripes running down the back. There are 6 larval instar stages. Larvae can be 6mm when hatched and up to 50mm when mature. Larvae are nocturnal and generally hide in the soil during the daytime. They can overwinter and continue feeding for up to 20 weeks, depending on available food.
• Pupa stage: are shiny, brown, smooth, and about 20mm in length. Cutworms can overwinter as pupae, which are found under the soil surface.

Confirmation

Examining soil around damaged (cut) plants will often reveal cutworm larvae. The larvae curl into a C shape when disturbed and remain motionless for a short period.

Problems with similar symptoms

Damage to foliar tissue is similar to that caused by other defoliating insect pests such as armyworm and grasshoppers.

Why and where it occurs

• Reduced tillage maize, weedy fields, or continuous cultivation of hosts encourages build up of cutworm.
• Adult moths lay hundred of eggs and their preferred laying site is moist soil or low-growing weeds - conditions common in no-till maize fields.
• Warmer growing conditions favor more generations. Up to four generations may occur during the growing season depending on species and latitude.

Host range

Cutworms are polyphagous with a very wide host range, including various vegetable and cereal crops such as asparagus, bean, beet, cabbage, castor bean, cotton, grape, lettuce, peanut, pepper, potato, radish, spinach, squash, strawberry, tobacco, rice, rye and tomato.

Geographical distribution

Worldwide distribution. In Central America, higher elevations favor cutworms.

Damage

• Mechanism of damage: Cutworms ‘cut’ the stem of seedlings, thus killing the plant. In severe cases replanting may be necessary. Older cutworms consume foliar material and burrow into the stem resulting in wilting and lodging of older plants. Most cutworm feeding takes place at night. Some may occur during the day, but cutworms generally remain sheltered below the ground at that time.
• When damage is important: Young seedlings (at the four leaf stage and below) are most vulnerable to cutworm damage as stems may be completely severed. Older plants are less vulnerable but damage may be severe if cutworms burrow into the stems.
• Cutworm incidence should be monitored using adult moth traps (light or pheromone) at the onset of the growing season to estimate intensity of infestation.
• Economic damage: Replanting may be required if the crop stand is severely damaged by cutworm feeding. Damage is most severe when a large number of cutworm larvae are present at seedling emergence. Each larva can destroy up to 4 plants. Yield loss as high as 47% has been recorded due to cutworm damage.

Management principles

Cultural control

• Plowing fields 3 to 6 weeks prior to planting will reduce cutworm infestation, by removing alternate hosts and disturbing eggs and overwintering pupae and larvae in the soil.
• Plowing under residue at the end of the growing season will prevent moths laying eggs on weeds in field.
• Maintaining weed-free fields following crop emergence will also help to reduce cutworm infestation.

Biological control

• Cutworms have many natural enemies including parasitic wasps, grasshoppers, viruses, and fungal pathogens. Natural predators should be encouraged by avoiding unnecessary treatment. In some cases biological control agents can be introduced to control cutworm infestation.

Chemical control

• Under severe cutworm infestation, insecticides may need to be applied. Insecticide should be applied when damage is at the early stages – when 3 to 10% of the crop is damaged. Incidence of cutworms is best assessed by using a flashlight at night to monitor cutworm presence and damage.

References

Davidson, R.H. and W.F. Lyon. 1987. Insect Pests of Farm, Garden and Orchard. Hoboken, NJ: John Wiley & Sons.

Eaton, A. 2000. Cutworms. University of New Hampshire Cooperative Extension. http://extension.unh.edu/Pubs/HGPubs/cutworms.pdf (8 November 2006).

King, A.B. and J.L. Saunders. 1984. The Invertebrate Pests of Annual Food Crops in Central America. London: Overseas Development Admin.

Kuhlman, D.E. and R.G. Dedert. 1987. Insect Pests of Maize in Zambia. Urbana – Champaign, IL: University of Illinois.

Kullik, S.A., M.K. Sears, D.G.R. McLeod, L.L. Gualtieri and A.W. Schaafsma. 2005. Phenology and field biology of black cutworm (Lepidoptera: Noctuidae) in Ontario no-till corn. Journal of Economic Entomology 98: 1594-1602. 

Li, Y., W.T. Wilsey, C.R. Weeden and A.M. Shelton. 2001. Cutworm (Peridroma saucia) – Life Cycle.  Pests in the Northeastern United States.  Cornell University. http://www.nysaes.cornell.edu/ent/factsheets/pests/cw.html (13 November 2006).

National Information System for the Regional IPM Centers. 2003. Crop Profile for Onions in Texas.  http://www.ipmcenters.org/cropprofiles/docs/txonions.html (13 November 2006).

Ortega, A. 1987. Insect pests of Maize: A Guide for Field Identification. Mexico, D.F.: CIMMYT.

Thakur, S.S. and J. Kumar. 1999. Estimation of avoidable losses caused by various insect pests in maize. Journal of Insect Science (Ludhiana) 12: 154-5. 

Contributors: Gabrielle Turner and Biswanath Das