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How to Manage Pests

UC Pest Management Guidelines


Variegated cutworm larva.

Cole Crops

Cutworms

Scientific Names:
Black cutworm: Agrotis ipsilon
Glassy cutworm: Crymodes devastator
Granulate cutworm: Agrotis subterranea
Variegated cutworm: Peridroma saucia

(Reviewed 6/07, updated 9/09)

In this Guideline:


DESCRIPTION OF THE PESTS

Cutworms include a number of species of dull gray to brown, medium-sized to large (up to 2 inches when full grown) caterpillars. Most cutworms curl up into a C-shape when disturbed. All normally feed close to the soil surface cutting off seedlings or damaging leaves resting on the ground. Most feeding occurs at night; during the day cutworms are usually found just below the soil surface or under dirt clods. First instar cutworms of some species may be found feeding on the leaf surface.

Adult cutworm moths have dark gray or brown front wings with irregular spots or bands and lighter hind wings. Females lay hundreds of white eggs, either singly or in clusters, depending on species, on leaves or stems close to the ground. After hatching, young larvae may feed on leaf surfaces for a while, but older larvae drop to the ground, tunnel into the soil, and emerge at night to feed.

DAMAGE

Seedlings or young plants are cut off at or just below ground level; often several plants in a row will be wilted or cut off. Losses can be especially severe in fields seeded to a stand or recently thinned. Occasionally cutworms will bore into cabbage heads, but this is not common. Damage often recurs in the same fields and same parts of fields from year to year; damage is worst where large numbers of cutworms are present before planting.

MANAGEMENT

Cutworms migrate into newly planted crops from surrounding weeds or infested crops. Check for cutworms in weeds around the edges of the field before you plant. Remove weeds from field margins and plow fields at least 10 days before planting to destroy larvae, food sources, and egg-laying sites. Cutworms have numerous natural enemies, but none can be relied on to bring a damaging population down below economic levels.

Organically Acceptable Methods
Cultural practices such as removal of adjacent weeds are an essential part of an organic management program.

Monitoring and Treatment Decisions
After the crop is up, check for a row of four or more wilted plants with completely or partially severed stems. If you find damaged plants, look for cutworms by digging around the base of plants and sifting the soil for caterpillars. If you find substantial numbers of cutworms, you can use bait to control most species, except the glassy cutworm, which occurs in the southern San Joaquin Valley. Baits are more effective when food is limited, so get it out before the crop emerges. If unexpected damage occurs after crop emergence, treat as soon as you find several severed plants in the same row.

Common name Amount/Acre R.E.I.+ P.H.I.+
(trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
When choosing a pesticide, consider information relating to natural enemies and honey bees as well as the environmental impact. Not all registered pesticides are listed. Always read label of product being used.
 
A. CARBARYL
  (Sevin) 5% bait 20–40 lb 12 3
  MODE OF ACTION GROUP NUMBER1: 1A
  COMMENTS: For broccoli, Brussels sprouts, cabbage, cauliflower.
 
B. CHLORPYRIFOS*
  (Lorsban Advanced) 2 pt 24 21
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Foliar application for Brussels sprouts. Avoid drift and tailwater runoff into surface waters.
  . . . or . . .
  (Lorsban Advanced) See label see comments see comments
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Preplant incorporated. Check label for rates, which vary according to crop and row spacing. REI is 24 hours, except for cauliflower, which is 3 days. PHI for cauliflower is 30 days, and 21 days for broccoli, Brussel sprouts, and cabbage.
 
C. DIAZINON*
  (Diazinon) 50W 4–8 lb 4 days 0
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Apply before planting. Avoid drift and tailwater runoff into surface waters.
 
D. ESFENVALERATE*
  (Asana XL) 2.4–5.8 fl oz 12 3
  MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: For broccoli, cabbage, cauliflower.
 
E. INDOXACARB
  (Avaunt) 2.5–3.5 oz 12 3
  MODE OF ACTION GROUP NUMBER1: 22
  COMMENTS: Do not apply more than 14 oz/acre/crop. Add a wetting agent to improve coverage. Minimum interval between sprays is 3 days.
 
F. METHOMYL*
  (Lannate) LV 1.5 pt 48 see comments
  (Lannate) 90SP 0.5 lb 48  
  MODE OF ACTION GROUP NUMBER1: 1A
  COMMENTS: Add a wetting agent to improve coverage. Preharvest interval is 3 days for broccoli, Brussels sprouts, and cauliflower and 1 day for cabbage. See label for other cole crops.
 
+ Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest.
* 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 are assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Cole Crops
UC ANR Publication 3442
Insects and Mites
E. T. Natwick, UC Cooperative Extension, Imperial County
Acknowledgments for contributions to Insects and Mites:
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
W. E. Chaney, UC Cooperative Extension, Monterey County
N. C. Toscano, Entomology, UC Riverside

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