How to Manage Pests

UC Pest Management Guidelines

Dry Beans

Cutworms

Scientific names:
Black cutworm: Agrotis ipsilon
Variegated cutworm: Peridroma saucia, and others

(Reviewed 6/18, updated 6/18)

In this Guideline:


DESCRIPTION OF THE PESTS

The variegated cutworm and the black cutworm can both cause damage to beans. Cutworm caterpillar larvae normally hide under debris on the soil surface during the day, and are active, voracious feeders at night. Fully-grown larvae range from 1 to 1.75 inches in length. If disturbed, they will often roll into a tightly coiled "C" shape.

Adult cutworm moths have dark gray or brown front wings with irregular spots or bands and lighter hind wings, with a wing span of 1.25 to 2 inches. Eggs are somewhat flattened on top, white to dull or off-white, and ribbed. They are generally deposited in masses of multiple irregular rows. Eggs may be deposited on crop foliage, but are also frequently found on weeds, close to the ground.

DAMAGE

Cutworms cause the most damage during spring and early summer months. They can cut young plants off at the base or near the ground level. Some may also climb up plants to feed on the foliage, leaving ragged holes in leaves.

MANAGEMENT

Cultural Control

Eliminate winter weeds within and adjacent to the field well before planting to reduce cutworm numbers in fields.

Organically Acceptable Methods

Use cultural controls for an organically certified crop.

Monitoring and Treatment Decisions

Start inspecting plants for cutworm damage when the crop emerges. Dig into the soil surface to determine the extent of the infestation and the size of the cutworms involved. If the cutworms are reducing the plant stand, apply an insecticide during the seedling stage. Frequently, the damage is most serious at the edges of a field but stand loss may occur in a spotty pattern throughout the field.

Common name Amount per acre** REI‡ PHI‡
(Example trade name)   (hours) (days)
Calculate impact of pesticide on air quality
Bee precaution pesticide ratings
Not all registered pesticides are listed. 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. Always read the label of the product being used.
 
A. BIFENTHRIN
  (Bifenture EC) 2.1–6.4 fl oz 12 14
  MODE-OF-ACTION GROUP NUMBER1: 3A
 
B. CYFLUTHRIN
  (Baythroid XL) 0.8–1.6 fl oz 12 7
  MODE-OF-ACTION GROUP NUMBER1: 3A
 
C. LAMBDA-CYHALOTHRIN
  (Warrior II with Zeon) 0.96–1.6 fl oz 24 21
  MODE-OF-ACTION GROUP NUMBER1: 3A
  COMMENTS: Do not graze livestock in treated areas or harvest vines for forage or hay.
 
D. ZETA-CYPERMETHRIN
  (Mustang Maxx) 1.8–4.0 fl oz 12 21
  MODE-OF-ACTION GROUP NUMBER1: 3A
 
E. SPINOSAD
  (Seduce Bait)# 20–44 lbs 4 28
  MODE-OF-ACTION GROUP NUMBER1: 5
** Mix with sufficient water to obtain full 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.
1 Rotate pesticides 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; pesticides with a 1B group number should be alternated with pesticides 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: Dry Beans
UC ANR Publication 3446

Insects and Mites

R. F. Long, UC Cooperative Extension, Yolo County
P. B. Goodell (emeritus), UC IPM Program

Acknowledgment for contributions to Insects and Mites:
L. D. Godfrey, Entomology, UC Davis

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