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How to Manage Pests

UC Pest Management Guidelines

| More pests | More crops | About guidelines |

Western yellowstriped armyworm larva.

Peppers

Western Yellowstriped Armyworm

Scientific name: Spodoptera praefica

(Reviewed 8/07, updated 8/07)

In this Guideline:

DESCRIPTION OF THE PEST

Adult moths of the western yellowstriped armyworm are difficult to distinguish from other nocturnal moths. They lay eggs in clusters covered with a gray, cottony material. Larvae of the western yellowstriped armyworm are caterpillars that measure about 1.5 inches (3.8 cm) long when fully grown. The caterpillar is usually black with one prominent stripe over many narrow bright ones on each side of its body. The head is a brown color with a netted pattern. There is also a large black spot above the first abdominal spiracle.

DAMAGE

Problems caused by the western yellowstriped armyworm may occur if peppers are planted near alfalfa or bean fields. This pest primarily feeds on leaves.

MANAGEMENT

Armyworms migrating into a field can be deterred by digging a trench or by a strip treatment of an insecticide on the perimeter of the field.

Cultural Control
A deep trench can be plowed with the steep side toward the peppers. This will often prevent movement of armyworm larvae into the crop.

Organically Acceptable Methods
Cultural controls and sprays of Bacillus thuringiensis or the Entrust formulation of spinosad are acceptable for use on an organically certified crop.

Monitoring and Treatment Decisions
If larvae are migrating to peppers from nearby fields and a trench can not be dug, treatment may be warranted. Treating only the field border may be effective.

Common name Amount/Acre** R.E.I.+ P.H.I.+
(trade name)   (hours) (days)
When choosing a pesticide, consider information relating to impact on natural enemies and honey bees and environmental impact. Not all registered pesticides are listed. Always read label of product being used.
 
A. BACILLUS THURINGIENSIS ssp. AIZAWAI#
  (various products) Label rates 4 0
  MODE OF ACTION GROUP NUMBER1: 11.B1
  COMMENTS: Bacillus thuringiensis preparations must be consumed by the larva to be effective. Coverage is critical for controlling this pest, especially between and under leaves and where leaves touch the fruit.
 
B. INDOXACARB
  (Avaunt) 3.5 oz 12 3
  MODE OF ACTION GROUP NUMBER1: 22
  COMMENTS: Minimum interval between sprays is 5 days. Do not apply more than 14 oz/acre/crop.
 
C. METHOXYFENOZIDE
  (Intrepid) Label rates 4 1
  MODE OF ACTION GROUP NUMBER1: 18A
  COMMENTS: An insect growth regulator. Apply at the beginning of egg hatch. Pheromone traps can be used to detect moth flight. When traps indicate a flight is occurring, monitor plants for eggs and treat when they appear. Do not apply more than 16 fl oz/acre/application or 64 fl oz/acre/season.
 
D. SPINOSAD
  (Entrust)# 1.25–2.5 oz 4 1
  (Success) 4–8 oz 4 1
  MODE OF ACTION GROUP NUMBER1: 5
  COMMENTS: Use higher rate for larger worms and heavy infestations. Best control is achieved when aimed at newly hatched larvae and coverage is thorough. More broad-spectrum than Bt but has very low toxicity to humans, vertebrates, and the adults of many natural enemies. Can remain toxic to larval stages (especially syrphid fly) for 5-7 days after treatment. Do not exceed 29 fl oz of Success or 9 oz of Entrust/acre/crop.
 
E. CRYOLITE
  (Kryocide) 8–12 lb 12 14
  MODE OF ACTION GROUP NUMBER1: 9A
 
 
**  See label for dilution rates.
+ 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.
# Acceptable for use on organically grown produce.
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: Peppers
UC ANR Publication 3460
Insects and Mites
E. T. Natwick, UC Cooperative Extension Imperial County
J. T. Trumble, Entomology, UC Riverside
Acknowledgment for contributions to Insects and Mites:
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
R. L. Coviello, UC Cooperative Extension, Fresno County
C. G. Summers, Kearney Agricultural Center, Parlier
W. E. Chaney, UC Cooperative Extension, Monterey County
C. F. Fouche, UC Cooperative Extension, San Joaquin County

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Statewide IPM Program, Agriculture and Natural Resources, University of California
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