How to Manage Pests

UC Pest Management Guidelines

Cotton

Alfalfa and Cabbage Loopers

Scientific Names:
Alfalfa looper: Autographa californica
Cabbage looper: Trichoplusia ni

(Reviewed 5/13, updated 5/13)

In this Guideline:


DESCRIPTION OF THE PESTS

Alfalfa and cabbage loopers are quite similar in appearance. The greenish larvae crawl by arching their bodies and are 1 to 1.5 inches long when mature. Looper eggs are similar to those of the bollworm in that they are spherical with vertical ridges from top to bottom. However, looper eggs are more flattened and have finer ridges. Alfalfa looper is usually found in May and early June while cabbage looper appears in late June through September.

Damage

Loopers feed on leaves, but the resulting ragged appearance of leaves is not important unless it is very extensive (more than 50%) and occurs during squaring. June defoliation is seldom sufficiently extensive to cause economic damage to cotton.

Management

Loopers are seldom numerous enough to cause significant damage and are usually kept under control by natural enemies. Moderate populations of loopers may be more beneficial than harmful, as they support populations of natural enemies that also attack the more destructive bollworms, budworms, and beet armyworms. In most cases, control is needed only where insecticides applied for other pests have reduced natural enemy populations; in the San Joaquin Valley, cabbage loopers often increase in numbers following treatment for lygus bugs. Occasionally, however, widespread outbreaks occur, apparently as a result of unusually favorable weather.

Biological Control

Many predators and parasites combine to substantially maintain looper populations at low levels. The eggs and small larvae are attacked by bigeyed bugs, minute pirate bugs, and other predators. Trichogramma parasites kill the eggs, and several other parasites, especially Hyposoter exiguae and Copidosoma truncatellum, attack the larvae. Loopers are also subject to a nuclear polyhedrosis virus that can reduce populations rapidly.

Cultural Control

The use of Bt cotton will help to reduce damage by loopers. A recently developed transgenic cotton, Bollguard II, offers suppression of a broader range of caterpillars than earlier Bt varieties and will also control caterpillars such as beet armyworms, cotton bollworm, pink bollworm, and tobacco budworm, which were not controlled by the earlier Bt varieties.

Organically Acceptable Methods

Biological control and sprays of Bacillus thuringiensis and the Entrust formulation of spinosad are acceptable for use on organically grown cotton.

Monitoring and Treatment Decisions

Damage by loopers is not important unless it is very extensive and occurs when it will affect the supply of energy to fruit. During the most vulnerable period, from first square to first open boll, plants can lose 20 to 25% of their leaf area without a reduction in yield. Before and after this period, plants can tolerate a loss of about half of the leaf area.

When loopers are numerous, ragging of leaves is usually obvious, and you will probably find the larvae while sweeping for lygus bugs or monitoring for other pests. Smaller loopers feed on older leaves where they are easily sampled using a beating sheet. Spread a 40-inch square piece of cloth between two rows of cotton and vigorously shake an arm's length of plants from one row onto the sheet. Lay the plants back and look for worms that are looping on the cloth. There are no specific treatment thresholds for loopers. If you find large numbers, check for signs of virus disease before applying an insecticide. Insecticides used for control, including Bacillus thuringiensis, are effective mainly against young larvae. Spot treatments are usually adequate for infestations on seedlings.

Common name Amount per acre** R.E.I.‡ P.H.I.‡
(example trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
 
The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least harmful to natural enemies, honey bees, and the environment are at the top of the table. When choosing a pesticide, also consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Not all registered pesticides are listed. Always read the label of the product being used.
 
A. BACILLUS THURINGIENSIS ssp. KURSTAKI#
  (various products) Label rates 4 0
  SELECTIVITY: High
  PERSISTENCE: Pest: Short NE:2 Short
  MODE OF ACTION GROUP NUMBER1: 11
  COMMENTS: Ground or air application. Not harmful to natural enemies.
 
B. METHOXYFENOZIDE
  (Intrepid 2F) 4–10 fl oz 4 14
  SELECTIVITY: High
  PERSISTENCE: Pest: Moderate NE:2 Moderate
  MODE OF ACTION GROUP NUMBER1: 18
  COMMENTS: An insect growth regulator.
 
C. INDOXACARB
  (Steward) Label rates 12 14
  SELECTIVITY: Moderate
  PERSISTENCE: Pest: Moderate NE:2 Moderate
  MODE OF ACTION GROUP NUMBER1: 22A
 
D. SPINOSAD
  (Entrust)# 1.25–2 oz 4 28
  (Success) 4–6 fl oz 4 28
  SELECTIVITY: High
  PERSISTENCE: Pest: Moderate NE:2 Short
  MODE OF ACTION GROUP NUMBER1: 5
  COMMENTS: Use of Success allowed under a supplemental 24(c) label.
 
E. NOVALURON
  (Diamond 0.83EC) 6–12 fl oz 12 30
  SELECTIVITY: Moderate to High
  PERSISTENCE: Pest: Moderate NE:2 Moderate
  MODE OF ACTION GROUP NUMBER1: 15
  COMMENTS: A chitin inhibitor.
 
F. CHLORANTRANILIPROLE
  (Coragen) 5.0–7.5 fl oz 4 21
  SELECTIVITY: High
  PERSISTENCE: Pest: Unknown NE:2 Short
  MODE OF ACTION GROUP NUMBER1: 28
 
G. FLUBENDIAMIDE
  (Belt SC) 2 oz 12 28
  SELECTIVITY: High
  PERSISTENCE: unknown
  MODE OF ACTION GROUP NUMBER1: 28
  COMMENTS: A newer material; impact on beneficials not yet determined. Highly toxic to honey bees.
 
H. ACEPHATE
  (Orthene 97) Label rates 24 21
  SELECTIVITY: Low
  PERSISTENCE: Pest: Moderate NE:2 Moderate
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Severe spider mite infestations may follow use as foliar spray.
 
I. METHOMYL*
  (Lannate SP) 0.12–0.25 lb 72 15
  SELECTIVITY: Low
  PERSISTENCE: Pest: Short NE:2 Short
  MODE OF ACTION GROUP NUMBER1: 1A
  COMMENTS: Kills eggs and larvae. Use may redden cotton. According to the label, do not make more than 8 applications/crop. Do not graze or feed cotton trash to livestock.
 
** Mix with sufficient water to provide complete 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 produced cotton.
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/.
2 NE = natural enemies

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Cotton
UC ANR Publication 3444

Insects and Mites

  • L. D. Godfrey, Entomology, UC Davis
  • P. B. Goodell, UC IPM Program and Kearney Agricultural Research and Extension Center, Parlier
  • E. T. Natwick, UC Cooperative Extension - Desert Research and Extension Center, Imperial County
  • D.R. Haviland, UC Cooperative Extension, Kern County and UC IPM Program
  • V. M. Barlow, UC Cooperative Extension, Riverside County and UC IPM Program
Acknowledgment for contributions to Insects and Mites:
  • E. E. Grafton-Cardwell, Kearney Agricultural Research and Extension Center, Parlier
  • N. C. Toscano, Entomology, UC Riverside

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