How to Manage Pests

UC Pest Management Guidelines

Strawberry

Cabbage Looper

Scientific Name: Trichoplusia ni

(Reviewed 6/08, updated 5/10)

In this Guideline:


DESCRIPTION OF THE PEST

Loopers are green caterpillars that have a narrow, white stripe along each side and several narrow lines down the back; they move with a characteristic arching or looping motion. Eggs are similar in appearance to corn earworm eggs but flatter and laid singly on the undersides of leaflets. Adult moths have brown, mottled forewings marked in the center with a small, silver figure 8.

DAMAGE

Young larvae feed primarily on the undersides of leaves, skeletonizing them. High populations can damage fruit but this is very uncommon.

MANAGEMENT

Treatments for loopers are seldom necessary in strawberries because they are frequently controlled by naturally occurring parasitic wasps. If treatments are necessary, time them to egg hatch.

Biological Control
Loopers are commonly controlled by parasitic wasps Hyposoter exiguae, Copidosoma truncatellum, and Trichogramma spp., and by outbreaks of nuclear polyhedrosis virus.

Organically Acceptable Methods
Biological controls, as well as sprays of Bacillus thuringiensis and the Entrust formulation of spinosad are acceptable for use on organically certified strawberries.

Monitoring and Treatment Decisions
Cabbage looper has only recently become a pest in strawberries, especially those planted next to lettuce fields. There are no established treatment thresholds for cabbage loopers in strawberries. If treatment is necessary, the preferred practice is to apply Bacillus thuringiensis just after egg hatch. Eggs are often found when monitoring mites with a leaf-brushing machine. Save a few leaves with eggs and observe when egg hatch begins and apply a treatment. When monitoring other pests, look for signs of looper feeding such as leaflets with holes, feces, and caterpillars feeding at the edge of a hole. If larvae are larger instars, an organophosphate such as diazinon may be needed to control them.

Common name Amount/Acre R.E.I.+ P.H.I.+
(trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
The following materials are listed in order of usefulness in an IPM program, taking into account efficacy and impact on natural enemies and honey bees. When choosing a pesticide, also consider information relating to environmental impact. Not all registered pesticides are listed. Always read label of product being used.
 
A. SPINOSAD
  (Entrust)# 1.25–1.5 oz 4 1
  (Success) 6 fl oz 4 1
  MODE OF ACTION GROUP NUMBER1: 5
  COMMENTS: Most effective against younger larvae. Rotate to an insecticide with a different mode of action after two successive applications. Maintaining proper pH of the spray tank water is critical for maximum efficacy.
 
B. BACILLUS THURINGIENSIS ssp. KURSTAKI#
  (various products) Label rates 4 0
  MODE OF ACTION GROUP NUMBER1: 11
  COMMENTS: Use when loopers are in the 1st or 2nd instar. Apply to plants when they are dry.
 
C. METHOXYFENOZIDE
  (Intrepid 2F) 6–12 fl oz 4 3
  MODE OF ACTION GROUP NUMBER1: 18
 
D. DIAZINON* 50WP 2 lb 3 days 5
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Do not use unless loopers pose a serious threat to the crop; diazinon is harmful to mite predators and outbreaks of twospotted spider mites may occur following its use. Do not allow this material to run off into surface waters.
 
+ 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: Strawberry
UC ANR Publication 3468

Insects and Mites

  • F. G. Zalom, Entomology, UC Davis
  • M. P. Bolda, UC Cooperative Extension, Santa Cruz County
  • S. K. Dara, UC Cooperative Extension, Santa Barbara County
  • S. Joseph, UC Cooperative Extension, Monterey County
Acknowledgment for contributions to the Insects and Mites:
  • P. A. Phillips, UC IPM Program and UC Cooperative Extension, Ventura County
  • N. C. Toscano, Entomology, UC Riverside

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