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UC Pest Management Guidelines


Color variations of tomato fruitworm (also called corn earworm and cotton bollworm).

Dry Beans

Corn Earworm

Scientific name: Helicoverpa zea

(Reviewed 8/07, updated 12/08)

In this Guideline:


DESCRIPTION OF THE PEST

Corn earworm moths are most active during evening and night. They are about 0.75 inch long, rather robust, with a wing span of 1 to 1.5 inches, and adults range in color from olive green, to tan, to dark reddish brown in color. Young larvae are greenish with black heads and conspicuous black hairs on the body. Fully developed worms are about 1.5 inches long and range in color from pale green or pinkish to brown.

DAMAGE

The corn earworm may be present throughout the season but is most abundant during August and September. In beans, larvae feed on leaves, buds, flowers, and within pods, often damaging the beans.

MANAGEMENT

Biological Control
Many predators and parasites attack corn earworm eggs, including several species of Trichogramma. Most parasitized eggs turn black, but there may be a lag period before they do so. Generalist predators such as lacewings, minute pirate bugs, and damsel bugs feed on corn earworm eggs and small larvae.

Organically Acceptable Methods
Biological control and sprays of Bacillus thuringiensis are organically acceptable.

Monitoring and Treatment Decisions
Sampling should start at bloom in conjunction with sampling for lygus bug populations. Inspect the sweep net for small worms. While sweeping is not an effective sampling method for corn earworms, the presence of small worms in the net indicates a problem may be developing. Beating and inspecting for worms on pans, sleds or sheets will provide some indication of the presence of small worms. There is no precise economic threshold established for initiating control for corn earworm on beans. On dry beans, treat when small worms appear in the sweep net and can be found generally throughout the field when young pods are present on plants.

Common name Amount/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 the impact on natural enemies and honey bees and environmental impact.
 
A. ACEPHATE
  (Orthene) 75 SP 1–1.33 lb 24 14
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Ground or air application. Highly toxic to honey bees; do not apply when bees are present. Do not feed treated forage, hay, or straw to livestock or use green pods for human food.
 
B. METHOMYL*
  (Lannate SP) 0.5–1 lb 48 14
  MODE OF ACTION GROUP NUMBER1: 1A
  COMMENTS: Highly toxic to honey bees; do not apply when bees are present. Do not apply more than 4.5 lb a.i./acre/crop.
 
C. BACILLUS THURINGIENSIS ssp. KURSTAKI#
  (various products) Label rates 4 0
  MODE OF ACTION GROUP NUMBER1: 11.B2
  COMMENTS: This material does not destroy natural enemies of corn earworm. Control is maximized by thorough coverage and by making applications when larvae are small.
 
D. SPINETORAM
  (Radiant) SC 4-8 fl oz 4 28
  MODE OF ACTION GROUP NUMBER1: 5
 
E. CARBARYL*
  (Sevin) XLR Plus 1–1.5 qt 12 see comments
  (Sevin) 80S 1.875 lb 12 see comments
  MODE OF ACTION GROUP NUMBER1: 1A
  COMMENTS: May result in outbreak of spider mites. Do not use on lentils in California. XLR Plus formulation is the least toxic to honey bees when direct application to bees is avoided and the spray residues have dried. Apply from late evening to early morning when bees are not foraging. Do not apply within 14 days of grazing or harvest for forage, within 3 days of harvest of fresh beans or peas, and within 21 days of harvest of dried beans, peas, seed, or hay.
 
F. LAMBDA-CYHALOTHRIN*
  (Warrior with Zeon) 3.84 oz 24 see comments
  MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: May cause outbreaks of mites. Preharvest interval (P.H.I.) is 7 days for succulent shelled or edible podded crops and 21 days for dried shelled crops.
 
G. ZETA-CYPERMETHRIN*
  (Mustang) 4.3 oz 12 see comments
  MODE OF ACTION GROUP NUMBER1: 3
  COMMENTS: May cause outbreaks of mites. Preharvest interval (P.H.I.) is 1 day for succulent shelled or edible podded crops and 21 days for dried shelled crops.
 
** 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.
# 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: Dry Beans
UC ANR Publication 3446
Insects and Mites
L. D. Godfrey, Entomology, UC Davis
R. F. Long, UC Cooperative Extension, Yolo County

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