How to Manage Pests

UC Pest Management Guidelines

Turfgrass

Cutworms and Armyworms

Scientific Names:
Black cutworm: Agrotis ipsilon
Variegated cutworm: Peridroma saucia
Granulate cutworm: Agrotis subterranea
Armyworm: Mythimna (= Pseudaletia) unipuncta

(Reviewed 9/09, updated 9/09, pesticides updated 12/16)

In this Guideline:


DESCRIPTION OF THE PESTS

Cutworms and armyworms are larvae of heavy-bodied, night-flying moths in the family Noctuidae. The white or greenish eggs of these noctuids are laid in masses, darkening as they approach hatching. Larvae can grow up to 2 inches (5 cm) long and typically curl up and lie still when disturbed.

Although damage is similar, armyworms are distinct from cutworms in their behavior. While cutworms are usually solitary feeders, armyworm eggs are laid in masses and larvae will feed as a group. When populations are high and food is scarce, armyworms will move as a group, feeding indiscriminately on plants in their path. Variegated cutworms are also known to march like armyworms when populations are high.

SUSCEPTIBLE SPECIES

All turfgrass species.

DAMAGE

Cutworms and armyworms are active from mid-March to October. They feed on leaves and crowns and may cut off plants near the soil surface. Larvae feed at night and hide in the thatch layer or in a burrow in the soil during the day. Turfgrass may be closely clipped around aeration holes, which larvae commonly occupy. Damage appears as circular spots of dead grass or depressed spots. Armyworms, especially, prefer damp areas.

MANAGEMENT

Manage armyworms or cutworms by dethatching the turfgrass and ensuring that irrigation does not cause wet areas in the turf. When monitoring indicates a need to treat, treatment choices include parasitic nematodes and Bacillus thuringiensis (Bt).

Biological Control

Larvae are parasitized by braconid wasps (Apanteles spp.) and by tachinid flies. Birds also commonly feed on armyworms and cutworms. The extensive contact noctuid larvae have with soil or thatch makes Steinernema carpocapsae nematodes a valuable control measure.

Cultural Control

Remove thatch to eliminate much of the daytime resting habitat for larvae. Avoid wet areas by irrigating according to evapotranspiration needs of turfgrass, because armyworms prefer laying eggs in damp areas containing stressed plants.

Monitoring and Treatment Decisions

Threshold levels are five larvae per square yard. Conduct a drench test (see MONITORING AND TREATING INSECTS AND MITES) to determine the infestation level. Consider treatment when there are more than five larvae per square yard. Mow and irrigate the site before applying insecticide and do not mow or irrigate the turfgrass for at least 24 hours after treatment unless nematodes were applied, in which case apply a post-treatment irrigation. Bacillus thuringiensis subsp. kurstaki (Bt) is not as effective against cutworms and armyworms as for sod webworms and should only be used on younger larval stages (first and second instars). When Bt is applied, do not irrigate for 2 days after treatment.

Common name Amount per 1000 sq ft** Ag Use
REI‡
NonAg Use
PHI‡
(Example trade name)   (hours) (days)

UPDATED: 12/16
Calculate impact of pesticide on air quality
Bee precaution pesticide ratings
The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees and the environment are at the top of the table. When choosing a pesticide, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Not all registered pesticides are listed. Always read the label of the product being used.
 
A. SPINOSAD
  (Conserve SC) Armyworms: 0.25 –1.2 fl oz 4 Until dry
    Cutworms: 0.8 –1.2 fl oz    
  MODE-OF-ACTION GROUP NUMBER1: 5
  COMMENTS: Use lower rate for control of light infestations of small larvae; the higher rate should be used for control of heavy infestations and large larvae. Delay watering or mowing of treated area for 12 –48 hrs after treatment. Do not reapply within less than 7 days. Toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.
 
B. BACILLUS THURINGIENSIS ssp. KURSTAKI
  (various products) Label rates 4 Until dry
  MODE-OF-ACTION GROUP NUMBER1: 11A
  COMMENTS: For young cutworm larvae. Apply to early instar larvae. Repeat application may be necessary. Breaks down rapidly in sunlight and washes readily off leaves. Do not irrigate for 2 days after treatment.
 
C. BACILLUS THURINGIENSIS ssp. AIZAWAI
  (various products) Label rates 4 Until dry
  MODE-OF-ACTION GROUP NUMBER1: 11A
  COMMENTS: For young armyworm larvae. Apply to early instar larvae. Repeat application may be necessary. Breaks down rapidly in sunlight and washes readily off leaves. Do not irrigate for 2 days after treatment.
 
D. STEINERNEMA CARPOCAPSAE 25 million NA NA
  COMMENTS: Store nematodes properly before use as directed. Apply to warm, moist, but not soggy soil. Several irrigations may be needed during 2 weeks after application to keep soil moist. Apply during the coolest time of day in hot areas.
 
E. AZADIRACHTIN
  (Azatrol, Neemix) Label rates 4 Until dry
  MODE-OF-ACTION GROUP NUMBER1: un
  COMMENTS: Most effective on young larvae. Can be used on both warm- and cool-season grasses.
 
F PYRETHRINS
  (various products) Label rates See label See label
  MODE OF ACTION: 3A
 
G. CHLORANTRANILIPROLE
  (Acelepryn) Label rates 4 Until dry
  (Acelepryn G) Label rates 4 after application complete
  MODE-OF-ACTION GROUP NUMBER: 28
 
H. CLOTHIANIDIN      
  (Arena 50 WDG) Label rates 12 Until dry
  (Arena 0.25 G) Label rates 12 When dust has settled.
  MODE-OF-ACTION GROUP NUMBER1: 4A      
  COMMENTS: Toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.
 
I. CARBARYL*
  (Sevin) 3 oz 12 Until dry
  MODE-OF-ACTION GROUP NUMBER1: 1A
  COMMENTS: Nontarget effects likely on other soil-dwelling organisms. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.
 
J. BIFENTHRIN
  (Talstar) Label rates Until dry
  MODE-OF-ACTION GROUP NUMBER1: 3A
  COMMENTS: Not for use on sod farms or in commercial seed production. May cause water quality issues. Highly toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.
 
** Apply spray in 25 gal water/1000 sq ft.
* Permit required from county agricultural commissioner for purchase or use.
1 Rotate chemicals with a different mode-of-action group number, and do not use products with the same mode-of-action group number more than twice per season to help prevent the development of resistance. For example, the organophosphates have a group number of 1B; chemicals with a 1B group number should be alternated with chemicals that have a group number other than 1B. Mode-of-action group numbers ("un"= unknown or uncertain mode of action) are assigned by IRAC (Insecticide Resistance Action Committee).
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Agricultural use applies to sod farms and commercial seed production.
NA Not applicable.
Indicates use is not listed on label.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Turfgrass
UC ANR Publication 3365-T

Insects and Mites

A. M. Sutherland, UC Statewide IPM Program, Alameda County
M. L. Flint, UC IPM Program, UC Davis
M. A. Harivandi, UC Cooperative Extension, Alameda County

Acknowledgment for contributions to Insect and Mites:
H. K. Kaya, Nematology, UC Davis
J. Hartin, UC Cooperative Extension, San Bernardino County
R. S. Cowles, Connecticut Agricultural Experiment Station, Windsor, CT
K. Kido, Entomology, UC Riverside
H. S. Costa, Entomology, UC Riverside
D. D. Giraud, UC Cooperative Extension, Humboldt/Del Norte counties

Top of page


Statewide IPM Program, Agriculture and Natural Resources, University of California
All contents copyright © 2017 The Regents of the University of California. All rights reserved.

For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See our Home page, or in the U.S., contact your local Cooperative Extension office for assistance.

Agriculture and Natural Resources, University of California

Accessibility   /PMG/r785300611.html revised: January 12, 2017. Contact webmaster.