How to Manage Pests

UC Pest Management Guidelines

Lettuce

Cutworms

Scientific Names:
Black cutworm: Agrotis ipsilon
Variegated cutworm: Peridroma saucia
Granulate cutworm: Feltia subterranea

(Reviewed 4/17, updated 4/17)

In this Guideline:


DESCRIPTION OF THE PESTS

Adult cutworm moths have dark gray or brown forewings 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. Cutworm larvae frequently roll into a "C" shape when disturbed.

Black cutworm larvae appear greasy gray to brown with several black bumps or tubercles on each segment. They may tunnel beneath the soil dragging parts of plants into the tunnel with them.

The variegated cutworm larva is from 1.5 to 2 inches long, yellow to brown, with a row of four to six dull yellow or pink diamond-shaped spots down the back.

The granulate cutworm varies in color, but is lighter than the black cutworm, and does not tunnel.

DAMAGE

Cutworms usually cut seedlings off at or just below the soil line. They may also bore into lettuce heads, and some species may damage the outer wrapper leaves.

Management

Monitoring and Treatment Decisions

Before planting, check for cutworms in surrounding weeds. After the crop is established, search for wilted plants or plants with severed stems. Dig around the base of injured plants and sift soil for these pests. Cutworms hide during the day and are found on the plants mostly at night.

Common name Amount per acre** REI‡ PHI‡
(Example trade name)   (hours) (days)
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. METHOXYFENOZIDE
  (Intrepid 2F) 4–8 fl oz 4 1
  MODE-OF-ACTION GROUP NUMBER1: 18A
 
B. ZETA-CYPERMETHRIN*
  (Mustang) 2.4–4.3 fl oz 12 1
  MODE-OF-ACTION GROUP NUMBER1: 3A
  COMMENTS: Maximum rate 28.5 fl oz/acre per season
 
C. PERMETHRIN*
  (Permethrin cutworm bait) 20–40 lb 12 1
  (Ambush, Pounce 25WP) Label rates 12 1
  MODE-OF-ACTION GROUP NUMBER1: 3A
  COMMENTS: Do not use if leafminers are present.
 
D. ESFENVALERATE*
  (Asana XL) Label rates 12 7
  MODE-OF-ACTION GROUP NUMBER1: 3
  COMMENTS: For use on head lettuce only. Do not use if leafminers are present.
 
** Mix with enough water to provide complete coverage.
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. Preharvest interval (PHI) 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).

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Lettuce
UC ANR Publication 3450

Insects and Other Arthropods

E. T. Natwick, UC Cooperative Extension, Imperial County
S. V. Joseph, UC Cooperative Extension, Monterey County
S. K. Dara, UC Cooperative Extension, Santa Barbara County

Acknowledgment for contributions to Insects and Mites:
N. C. Toscano, Entomology, UC Riverside

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