How to Manage Pests

UC Pest Management Guidelines

Citrus

Fruittree Leafroller

Scientific Name: Archips argyrospila

(Reviewed 2/17, updated 2/17, corrected 1/19)

In this Guideline:


Description of the Pest (View caterpillar ID key)

Larvae of the fruittree leafroller are green caterpillars that are somewhat flattened and have shiny black heads. The caterpillars tie or roll leaves or blossoms together with silken threads and feed inside these nests. Older caterpillars construct a new nest frequently, often daily. Mature caterpillars pupate inside nests or in thin cocoons on branches or the trunk. Moths emerge about 8 to 12 days later; after mating, females lay egg masses on twigs in the upper part of trees. Eggs overwinter and start hatching in the middle of March; there is only one generation a year.

Damage

Fruittree leafrollers can occasionally cause damage in spring by feeding on newly set fruit or on ripening Valencias, navels, or grapefruit. Early in spring, young larvae feed mostly on new growth flushes, often resulting in curled leaf terminals. In situations where most of the new flush is consumed (e.g., weak or drought stressed trees with little flush), larvae will tie leaves to fruit and bore inside; this injury provides entry sites for secondary decay organisms, and fruit will drop within 1 to 2 weeks.

Management

Fruittree leafroller is a minor pest. Monitor for fruittree leafroller in spring at the same time as citrus cutworm, but count the two species separately. Natural enemies generally are helpful in reducing this pest, and pesticide applications are rarely necessary.

Biological Control

Natural enemies include general predators that prey on small larvae, and Trichogramma spp. that parasitize the eggs.

Organically Acceptable Methods

Use biological control and sprays of Bacillus thuringiensis in organically certified crops.

Selectivity

The Bacillus thuringiensis (Bt) insecticides (Dipel and Javelin) are toxic only to caterpillar pests. The stomach poison cryolite is specific to foliage-feeding pests. These in­secticides are relatively nontoxic to parasites that attack the caterpillars and beneficial in­sects and mites that feed on other citrus pests. The broad-spectrum carbamates (Lannate) kill many of the beneficial insects and mites in citrus groves.

Monitoring and Treatment Decisions

To monitor fruittree leafroller eggs, establish one or two permanent observation trees per site at five locations per block. Before the middle of March, check twigs and small branches thoroughly in the upper one-third of the tree for gray to brown, flat egg masses.

To monitor caterpillars, search the outer canopy of the south and east side of four trees at each sampling site. Spend about 2 to 5 minutes per tree and count all the live leafroller cat_erpillars. Carry out this procedure in five locations per block. Record the number of worms per unit time and calculate the average number of larvae per hour search. Caterpillars can also be monitored with an L-shaped 1/4 square meter (20 x 20 inches) PVC pipe counting frame to count the number of infested vs. noninfested terminals. Be sure to open nests and count only nests that contain a live worm. Begin counts once a week when the spring feather-leaf flush appears or the first fruittree leafroller caterpillar is seen. Take one sam_ple from the NE corner of 20 randomly selected trees in a diagonal through the block.

When mature fruit are present and 20% or more of the new flush terminals are infested with a live worm, watch carefully for leaves being attached to mature fruit. The potential for damage to mature fruit is greatest at this point. The 20% threshold corresponds to a time search number of about 400 worms per hour. If worms are close to pupating, increase the threshold, especially if fruit is not present. Most larvae pupate before petal fall and pesticides are usually not needed.

Common name Amount to use REI‡ PHI‡
(Example trade name) (type of coverage)** (hours) (days)
Calculate impact of pesticide on air quality
Bee precaution pesticide ratings
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 rate (OC) 4 0
  RANGE OF ACTIVITY: Pests: narrow (caterpillars); Natural enemies: none
  PERSISTENCE: Pests: short; Natural enemies: none
  MODE-OF-ACTION GROUP NUMBER1: 11A
  COMMENTS: Can be used during bloom. Timing is important because of short residual period. Apply only during warm weather to control young, actively feeding worms. Use reduced wind velocity and drive 3 mph
 
B. CRYOLITE
  (Prokil Cryolite 96) 8–20 lb/acre (OC) 12 15
  (Kryocide) 8–20 lb/acre (OC) 12 15
  RANGE OF ACTIVITY: Pests: intermediate (foliage feeders such as worms, katydids, and Fuller rose beetle); Natural enemies: few, if any
  PERSISTENCE: Pests: long, unless washed off by rain; Natural enemies: none to short
  MODE-OF-ACTION GROUP NUMBER1: 8C
  COMMENTS: Check label for variety. Use higher rate for larger trees. Slow-acting stomach poison that may take several days of warm weather to kill worms. Use reduced wind velocity and a speed of 3 mph. Use of Prokil Cryolite 96 allowed under a supplemental label.
 
C. CARBARYL*
  (Sevin XLR Plus) 2–3 qt/acre (OC) 12 5
  RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
  PERSISTENCE: Pests: long; Natural enemies: long
  MODE-OF-ACTION GROUP NUMBER1: 1A
  COMMENTS: For use on all varieties. During the bloom period, apply from 1 hour after sunset until 2 hours before sunrise. Check with your local county agricultural commissioner regarding application restrictions during the bloom period.
 
D. NALED
  (Dibrom 8 Emulsive)* 1–2 pt/acre (OC) 48 7
  RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
  PERSISTENCE: Pests: short; Natural enemies: intermediate
  MODE-OF-ACTION GROUP NUMBER1: 1B
  COMMENTS: For use on grapefruit, lemons, oranges, tangerines. This pesticide is hazardous to honey bees; do not use during bloom.
 
E. METHOMYL*
  (Lannate LV2.4) 1.5–3 pt/acre (OC) 3 days 1
  RANGE OF ACTIVITY: Pests: broad (many insects); Natural enemies: most
  PERSISTENCE: Pests: short; Natural enemies: intermediate
  MODE-OF-ACTION GROUP NUMBER1: 1A
  COMMENTS: For use on grapefruit, lemons, oranges, tangerines, and tangelos. Apply as needed, except during daylight hours of the bloom period.
** A - Aircraft applications 5 to 20 gal water/acre.
  OC - Outside coverage uses 100 to 250 gal water/acre.
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.
* Permit required from county agricultural commissioner for purchase or use.
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 (un = unknown or uncertain mode of action) are assigned by IRAC (Insecticide Resistance Action Committee).

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Citrus
UC ANR Publication 3441

Insects, Mites, and Snails

E. E. Grafton-Cardwell, Lindcove Research and Extension Center, Exeter and Entomology, UC Riverside
J. G. Morse, Entomology, UC Riverside
D. R. Haviland, UC Cooperative Extension, Kern County and UC IPM Program
B. A. Faber, UC Cooperative Extension, Santa Barbara and Ventura counties

Acknowledgments for contributions to Insect, Mite, and Snails:
J. Barcinas, E.S.I., Corona, CA
R. Dunn, Badger Farming Co., Exeter, CA
J. Gorden, Pest Management Associates, Exeter, CA
C. E. Kallsen, UC Cooperative Extension, Kern County
D. Machlitt, Consulting Entomology Services, Moorpark, CA
C. Musgrove, retired entomologist, Riverside, CA
K. Olsen, S & J Ranch, Pinedale, CA
N. V. O'Connell, UC Cooperative Extension, Tulare County
P. A. Phillips, UC IPM Program, UC Cooperative Extension, Ventura County
T. Roberts, E.S.I., Corona, CA
T. Shea, UC Cooperative Extension, Riverside County
J. Stewart, Pest Management Associates, Exeter, CA
P. Washburn, Washburn & Sons Citrus Pest Control, Riverside, CA

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