Agriculture: Strawberry Pest Management Guidelines

Cabbage Looper

Trichoplusia ni

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 with the help of three pairs of true legs in the front and three pairs of false legs towards the end. Eggs are similar in appearance to corn earworm eggs but are 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 numbers can damage fruit but this is very uncommon.

Management

Insecticide applications for loopers are seldom necessary in strawberries because they are frequently controlled by naturally occurring parasitic wasps and seldom feed on fruit. If insecticide applications 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

Use biological controls, as well as sprays of Bacillus thuringiensis and the Entrust formulation of spinosad on organically certified strawberries.

Monitoring and Treatment Decisions

Cabbage looper is most likely to become a pest in strawberries when the field is planted next to lettuce fields. There are no established treatment thresholds for cabbage loopers in strawberries. If an insecticide application 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 an insecticide. 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.

Common name Amount per acre REI‡ PHI‡
(Example trade name) (hours) (days)
Not all registered pesticides are listed. 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, consider information relating to air and water quality, resistance management, and the pesticide's properties and application timing. Always read the label of the product being used.
 
A. BACILLUS THURINGIENSIS ssp. KURSTAKI#
  (Various products) Label rates 4 0
  MODE-OF-ACTION GROUP NUMBER1: 11A
  COMMENTS: Use when loopers are in the first or second instar stage. Apply to plants when they are dry.
 
B. BACILLUS THURINGIENSIS ssp. AIZAWAI#
  (Agree WG) Label rates 4 0
  MODE-OF-ACTION GROUP NUMBER1: 11A
 
C. SPINOSAD
  (Entrust)# 1.25–2 oz 4 1
  (Success) 4–6 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. Toxic to bees; do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.
 
D. METHOXYFENOZIDE
  (Intrepid 2F) 6–12 fl oz 4 3
  MODE-OF-ACTION GROUP NUMBER1: 18
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) 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.
# Acceptable for use on organically grown produce.
1 Rotate insecticides 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. Mode-of-action group numbers for insecticides and miticides (un=unknown or uncertain mode of action) are assigned by IRAC (Insecticide Resistance Action Committee).
Text Updated: 07/18
Treatment Table Updated: 07/18