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How to Manage Pests

UC Pest Management Guidelines


Variegated cutworm larva.

Corn

Cutworms

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

(Reviewed 1/06, updated 8/08)

In this Guideline:


DESCRIPTION OF THE PESTS

Adults are moths approximately 1 inch long with a wing span of 1.25 to 2 inches and vary widely in coloration. Eggs are somewhat flattened on top, white to dull or off-white in color, and ribbed. They are generally deposited in massed rows. Eggs may be deposited on crop foliage, but are frequently found on weeds. Fully grown larvae range from 1 to 1.75 inches in length and commonly curl into a C-shape when disturbed.

Cutworms are most active and cause the most damage during spring and early summer months. The larvae normally hide under debris on the soil surface during the day, but are active, voracious feeders at night. Some cutworms climb into the host plant to feed, but many stay on the ground, cutting seedling host plants off at or just below the soil surface.

DAMAGE

Cutworms cut young plants off at the base or near the ground level. Usually, it is necessary to dig in the soil to find cutworm larvae and to determine the extent of the infestation and the size of the cutworms involved.

MANAGEMENT

If the cutworm population is reducing the plant stand, treat during the seedling stage. Frequently, the damage is most serious at the edges of a field, but stand loss can occur in a spotty pattern throughout the field. Treatment of hot spots may be possible. Seedlings will regrow if damage is above the growing point.

Organically Acceptable Methods
Eliminating weeds 2 weeks before planting both within and adjacent to the field can help to minimize cutworm problems in an organically managed crop.

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

  Calculate impact of pesticide on air quality
The following materials are listed in order of usefulness in an IPM program, taking into account efficacy, information related to natural enemies and honey bees and environmental impact. Not all registered pesticides are listed. Always read label of product being used.
 
A. PERMETHRIN*
  (Ambush) 25W 6.4–12.8 fl oz 12 1
  MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: Apply as a foliar application before brown silk stage.
 
B. CHLORPYRIFOS*
  (Lorsban) 4E 1–2 pt 12 Grain or ears: 21
Livestock feed: 35
        Grazing or silage: 14
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Not for use on popcorn. Avoid drift and tailwater runoff into surface waters. Do not apply more than 6 pt/acre/season. Do not make more than 3 applications/season.
 
C. CARBARYL
  (Sevin) 5% Bait 40 lb 12 see label
  MODE OF ACTION: A carbamate (Group 1A)1 insecticide.
  COMMENTS: Ground or air application. Use only fresh bait. Apply in late afternoon or early evening so bait stays fresh longer. Avoid direct application to lakes, streams, ponds. Do not apply when weather conditions favor drift from treated areas. Do not contaminate water, food, or feed when cleaning equipment or disposing of wastes.
 
** Mix with sufficient water to obtain full coverage.
+ 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: Corn
UC ANR Publication 3443
Insects and Mites
L. D. Godfrey, Entomology, UC Davis
S. D. Wright, UC Cooperative Extension, Tulare County
C. G. Summers, Kearney Agricultural Center, Parlier
C. A. Frate, UC Cooperative Extension, Tulare County
Acknowledgement for contributions to Insect and Mites:
M. J. Jimenez, UC Cooperative Extension, Tulare County

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