Agriculture

Beet Armyworm

  • Spodoptera exigua
Updated: 05/2010

Tools

PestManage: a decision support tool to view and compare pest management options

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.

Pesticides and Natural Enemy Releases

Not all registered pesticides are listed. The following are ranked by their IPM value, with the most effective and least harmful to natural enemies, honey bees, and the environment listed at the top of the table. When choosing a pesticide, consider information related to water and air quality, resistance management, and the pesticide's properties and application timing. Use PestManage to compare summarized management options for different pests in the same crop. Always carefully read the label of the product being used and take all necessary precautions when handling pesticides.

Rank Active ingredient Example trade name Group Group Order MoA 1 Amount per acre REI (hours) ‡ PHI (days) ‡ Comments Selectivity 2 Bees 3 Predatory mites 4 Predators 5 Parasitoids 5 Residue duration 6 Leaching(fish) 7 Adsorbed runoff(fish) 8 Solution runoff(human) 9 Leaching(human) 10 Solution runoff(human) 11 Last updated 12
I
various products # Application Timing Varies (See UC IPM Pest Management Guidelines and Label) 8

11A

Label rates 4 0 Must be consumed by the larva to be effe... narrow II low low low short — — — — — 06/2016
B
Coragen Application Timing Varies (See UC IPM Pest Management Guidelines and Label) 8

28

3.5–5.0 fl oz 4 1 Can be applied both through the drip lin... narrow III — — — — — — — — — 06/2016
D
Voliam Xpress Application Timing Varies (See UC IPM Pest Management Guidelines and Label) 8

28/3A

6.0–9.0 fl oz 24 5 — — — — — — — — — — — — 06/2016
E
Voliam Flexi Application Timing Varies (See UC IPM Pest Management Guidelines and Label) 8

28/4A

4.0–7.0 oz 12 1 Review and follow the California neonico... — I — — — — — — — — — 06/2016
C
Exirel Application Timing Varies (See UC IPM Pest Management Guidelines and Label) 8

28

7–13.5 fl oz 12 1 Highly toxic to bees; do not spray direc... narrow I — — — — very low very low low low low 06/2016
C
Verimark Application Timing Varies (See UC IPM Pest Management Guidelines and Label) 8

28

5–10 fl oz 4 1 Highly toxic to bees; do not spray direc... narrow I — — — — very low very low low low low 06/2016
K
Asana XL Application Timing Varies (See UC IPM Pest Management Guidelines and Label) 8

3A

5.8–9.6 fl oz 12 7 Do not exceed 0.35 lb a.i./acre per seas... broad I high moderate high moderate high intermediate extra high low intermediate 06/2016
A
Avaunt Application Timing Varies (See UC IPM Pest Management Guidelines and Label) 8

22A

3.5 oz 12 3 Minimum interval between sprays is 5 day... narrow I — low low moderate low low intermediate very low low 06/2016
J
*
Lannate LV Application Timing Varies (See UC IPM Pest Management Guidelines and Label) 8

1A

1.5–3 pt 48 3 Do not use if psyllids are present. High... broad I high high high moderate — — — — — 06/2016
J
*
Lannate SP Application Timing Varies (See UC IPM Pest Management Guidelines and Label) 8

1A

0.5–1 lb 48 3 Do not use if psyllids are present. High... broad I high high high moderate — — — — — 06/2016
F
Intrepid 2F Application Timing Varies (See UC IPM Pest Management Guidelines and Label) 8

18

Label rates 4 1 Do not apply more than 16 fl oz/acre per... narrow II low low low short very low low low very low low 06/2016
G
Radiant SC Application Timing Varies (See UC IPM Pest Management Guidelines and Label) 8

5

5–10 fl oz 4 1 Is more efficacious and has longer resid... narrow II moderate moderate 13 low/moderate moderate 14 low low low very low low 06/2016
H
Entrust # Application Timing Varies (See UC IPM Pest Management Guidelines and Label) 8

5

1.25–2.5 oz 4 1 Use higher rate for larger worms and hea... narrow II moderate moderate 13 low/moderate moderate 13 very low low low very low low 06/2016
H
Success Application Timing Varies (See UC IPM Pest Management Guidelines and Label) 8

5

4–8 oz 4 1 Use higher rate for larger worms and hea... narrow II moderate moderate 13 low/moderate moderate 13 very low low low very low low 06/2016
—
No information.
I
Do not apply or allow to drift to plants that are flowering including weeds. Do not allow pesticide to contaminate water accessible to bees including puddles.
II
Do not apply or allow to drift to plants that are flowering including weeds, except when the application is made between sunset and midnight if allowed by the pesticide label and regulations. Do not allow pesticide to contaminate water accessible to bees including puddles.
III
No bee precaution, except when required by the pesticide label or regulations.
  • ‡ a b Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without personal protective equipment. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases, the REI exceeds the PHI. The longer of the two intervals is the minimum time that must elapse before harvest.
  • * a b  Permit required from county agricultural commissioner for purchase or use.
  • # a b  Acceptable for use on certified organic crops. Check with your certifier to confirm before application.
  • 1 ↩ Group numbers for insecticides and miticides are assigned by the Insecticide Resistance Action Committee (IRAC). Insecticides with unknown modes of action are assigned mode-of-action group numbers (MoAs) that begin with UN. 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; insecticides with a 1B group number should be alternated with insecticides that have a group number other than 1B.
  • 2 ↩ Range of insect and mite groups affected by a pesticide. Broad means the pesticide affects most groups of insects and mites; narrow means the pesticide affects only a few specific groups.
  • 3 ↩ Risk of harm to honey bees. For more information, see Bee Precaution Pesticide Ratings.
  • 4 ↩ Risk of harm to predatory mites. Toxicities are generally to western predatory mite, Galendromus occidentalis. Where differences have been measured in toxicity of the pesticide-resistant strain versus the native strain, these are listed as pesticide-resistant strain or native strain.
  • 5 a b Risk of harm to parasitoids and general predators. Toxicities are averages of reported effects and should be used only as a general guide. Actual toxicity of a specific insecticide depends on factors including the application rate, environmental conditions, and the life stage and species of a parasitoid or predator.
  • 6 ↩ Length of time residue affects natural enemies. Short means hours to days; moderate means days to 2 weeks; and long means many weeks or months.
  • 7 ↩ Risk of harm to fish from leaching, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
  • 8 ↩ Risk of harm to fish from adsorbed runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
  • 9 ↩ Risk of harm to fish from solution runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
  • 10 ↩ Risk of harm to humans from leaching, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
  • 11 ↩ Risk of harm to humans from solution runoff, based on USDA Natural Resources Conservation Service Windows Pesticide Screening Tool (WIN-PST).
  • 12 ↩ Date information was last updated in the UC IPM Pest Management Guidelines.
  • 13 a b c d e Toxic to some natural enemies (lacewing and syrphid fly larvae, predatory beetles, and thrips) when sprayed and up to 5 to 7 days after.
  • 14 ↩ Residual is moderate if solution is between a pH of 7 and 8.
UC Peer Reviewed Logo

UC IPM Pest Management Guidelines: Peppers
UC ANR Publication 3460

E.T. Natwick (emeritus), UC Cooperative Extension Imperial County

J.T. Trumble, Entomology, UC Riverside

J.L. Aguiar, UC Cooperative Extension Riverside County

Acknowledgement for Contributions to Invertebrates

W.J. Bentley (emeritus), UC IPM and Kearney Agricultural Research and Extension Center, Parlier

W.E. Chaney (emeritus), UC Cooperative Extension Monterey County

R.L. Coviello, UC Cooperative Extension Fresno County

C.F. Fouche, UC Cooperative Extension San Joaquin County

C.G. Summers (emeritus), Entomology, UC Davis and Kearney Agricultural Research and Extension Center, Parlier

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