How to Manage Pests

UC Pest Management Guidelines

Peppers

Beet Armyworm

Scientific name: Spodoptera exigua

(Reviewed 12/09, updated 5/10)

In this Guideline:


DESCRIPTION OF THE PEST

Adult beet armyworms are small, mottled-gray or dusky-winged moths. Females lay eggs in clusters on leaves; the clusters are covered with fluffy, dirty white scales. Eggs hatch in a few days and tiny caterpillars begin feeding while still clustered together on the plant. In 2 to 3 weeks beet armyworm larvae are full grown and about 1 inch long. The body is smooth with few hairs and predominantly green with mottled dark lines along the back. Just above the spiracle, lengthwise along the body, is a dark green to black line edged on each side with white. There is usually a small dark spot above the spiracle on the second pair of true legs.

In addition to peppers, beet armyworm feeds on sugarbeet, alfalfa, beans, tomatoes, and a variety of weeds such as lambsquarters, redroot pigweed, and nettleleaf goosefoot. During winter and spring, the population is concentrated on weeds, but in late spring moths begin laying eggs in the pepper field when the plants are young. Newly hatched larvae feed together near the egg cluster and gradually disperse as they grow; they skeletonize leaves and may spin a loose webbing over the feeding site. Older larvae chew irregular holes in leaves and feed on young fruit.

DAMAGE

Beet armyworm is a serious pest of peppers. It feeds on both leaves and fruit. As the fruit forms, beet armyworm bores into the calyx end. Both defoliation and fruit loss result from the feeding. Unlike many caterpillar pests, the feeding is quite messy, with webbing and excrement present.

MANAGEMENT

Regular monitoring of the leaves and fruit is important in detecting an infestation of beet armyworms. Treatments may be necessary if fruit damage is occurring.

Biological Control

Many natural enemies attack beet armyworms. Among the most common parasites are the wasps Hyposoter exiguae and Chelonus insularis, and the tachinid fly Lespesia archippivora. Viral diseases may also be important; however, none of these organisms provide reliable control of armyworms when they feed on the fruit.

Organically Acceptable Methods

Biological control and sprays of Bacillus thuringiensis or the Entrust formulation of spinosad are acceptable for use on an organically certified crop.

Monitoring and Treatment Decisions

Sampling guidelines for beet armyworm in peppers have not been developed. Pheromone traps are useful for determining when major flights occur but not for predicting damage. Look for the cream-colored egg mass or, later, for the feeding on the seedlings and leaves to determine if beet armyworms are present. Also, sample fruit when it first appears. A 5-minute timed search is useful in determining the need for treatment. On average, if one or more larvae or egg masses are found in 5 minutes, treatments may be justified. Ground applications provide maximum effectiveness of the pesticide. Treat if beet armyworms are on the fruit.

Common name Amount per 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 impact on natural enemies and pollinators and environmental impact. Not all registered pesticides are listed. Always read label of product being used.
 
A. INDOXACARB 3.5 oz 12 3
  (Avaunt)
  MODE-OF-ACTION GROUP NUMBER1: 22A
  COMMENTS: Minimum interval between sprays is 5 days. Do not apply more than 14 oz/acre per crop.
 
B. CHLORANTRANILIPROLE 3.5–5 fl oz 4 1
  (Coragen)
  MODE-OF-ACTION GROUP NUMBER1: 28
  COMMENTS: Can be applied both through the drip line and by foliar spray.
 
C. METHOXYFENOZIDE Label rates 4 1
  (Intrepid)
  MODE-OF-ACTION GROUP NUMBER1: 18
  COMMENTS: Do not apply more than 16 fl oz/acre per application or 64 fl oz/acre per season.
 
D. SPINETORAM 5–10 fl oz 4 1
  (Radiant SC)
  MODE-OF-ACTION GROUP NUMBER1: 5
  COMMENTS: Is more efficacious and has longer residual activity than spinosad.
 
E. SPINOSAD 1.25–2.5 oz 4 1
  (Entrust)# 4–8 oz 4 1
  (Success)
  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. 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 per crop.
 
F. BACILLUS THURINGIENSIS ssp. AIZAWAI# Label rates 4 0
  (various products)
  MODE-OF-ACTION GROUP NUMBER1: 11
  COMMENTS: 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. Control is most effective against newly hatched worms.
 
G. METHOMYL* 0.25–0.5 lb 48 3
  (Lannate SP) 0.75–1.5 pt 48 3
  (Lannate LV)
  MODE-OF-ACTION GROUP NUMBER1: 1A
  COMMENTS: Do not use if psyllids are present.
 
H. ESFENVALERATE* 5.8–9.6 fl oz 12 7
  (Asana XL)
  MODE-OF-ACTION GROUP NUMBER1: 3
  COMMENTS: Do not exceed 0.35 lb a.i./acre per season. If leafminers are present in the pepper crop, use of this product should be limited to late in the season to minimize negative impacts on biological control.
 
I. CRYOLITE 8–12 lb 12 14
  (Kryocide)
  MODE-OF-ACTION GROUP NUMBER1: un
 
** 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.
* Permit required from county agricultural commissioner for purchase or use.
# 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 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
Jose Aguiar, UC Cooperative Extension, Riverside County
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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