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How to Manage Pests

UC Pest Management Guidelines

Mature larva of fruittree leafroller, Archips argyrospila, in partially opened webbed leaf.


Fruittree Leafroller

Scientific Name: Archips argyrospila

(Reviewed 6/06, updated 4/09)

In this Guideline:


Adult fruittree leafroller moths are about 0.5 inch long, with rusty brown wings marked with areas of white and gold. When at rest, the adults show the typical bell-shaped pattern common to the family Tortricidae. The eggs are laid in masses on limbs and twigs and are covered with a gray secretion that turns white upon aging. Larvae are green with a black head. The intensity of the green color varies from a light green in young larvae to a darker green as they mature.

The fruittree leafroller overwinters in the egg stage. Eggs usually hatch in early spring. Larvae feed within opening buds. As they mature they tie leaves together and feed on leaves, blossoms, and small fruit. Adults emerge in May or June. These adults then lay egg masses that overwinter. There is one generation per year.


During bloom, larvae feed on leaves and buds. Later in the season they can feed on the surface of fruit, causing severe damage to fresh market prunes. Fruit may become infected with brown rot at feeding wounds.


Dormant treatments and bloomtime Bacillus thuringiensis (Bt) applications for other pests help keep leafroller populations under control. Leafroller damage is not a problem for prunes grown for the dried market but needs to be monitored on fresh market prunes from bloom to petal fall each season so that prompt action can be taken if damaging populations develop.

Biological Control
A number of parasites, including species of Macrocentrus, Cotesia (=Apanteles), and Exochus, attack leafroller larvae. General predators such as lacewings, assassin bugs, and minute pirate bugs may feed on eggs and larvae. Preservation of natural enemy populations is an important part of keeping leafroller numbers low. Use selective materials that are least disruptive of biological control when treating other pests.

Organically Acceptable Methods
Fruittree leafroller can be managed organically with oil sprays during the dormant season followed by bloom treatments of Bacillus thuringiensis or petal fall sprays of the Entrust formulations of spinosad. These treatments are also used to manage leafrollers, peach twig borer, cankerworms, and green fruitworm.

Monitoring and Treatment Decisions
Although a separate treatment for fruittree leafroller control is seldom needed, inspect orchards during the dormant period for unusually large numbers of egg masses. Egg masses are about the size of a thumb-print and laid on smooth wood. Also check flower clusters during bloom for the presence of the fruittree leafroller and other larvae in fresh market prunes. View photos to identify caterpillars present during bloom. If damaging populations are observed, a number of environmentally sound chemicals are effective in controlling this pest, including Bacillus thuringiensis, spinosad (Entrust, Success), methoxyfenozide (Intrepid), and diflubenzuron (Dimilin).

Fruit damage sample. In mid-July, take a fruit damage sample to assess the overall effectiveness of the current year's IPM program and to determine next year's needs. For more information, see FRUIT EVALUATION AT HARVEST. Record on a monitoring form (84 KB, PDF) the number of fruit infested by larvae, type of larvae present, whether the damage is surface feeding only or if the larvae penetrated the fruit.

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

Calculate impact of pesticide on air quality
Bee precaution pesticide ratings
The following materials are listed in order of usefulness in an IPM program, taking into account efficacy, impact on natural enemies and honey bees, and impact of the timing on beneficials. When choosing a pesticide, also consider information relating to environmental impact. Not all registered pesticides are listed. Always read label of product being used.
  (various products) Label rates 4 0
  COMMENTS: Make two applications during bloom: the first between popcorn and the beginning of bloom and the second 7–10 days later, but no later than petal fall. Compatible with fungicide sprays, and can be tank mixed with them. Good coverage is essential. Ground application using a concentrate rate (80–100 gal water maximum) is preferred. If aerial applications must be made because conditions do not permit ground application, a concentrate rate (5 gal or less) is preferred. Fly material on at a height of about 20 ft over the canopy using appropriate nozzles to allow better deposition on the tree tops.
  (Entrust)# 1.71–2.5 oz 0.43–0.6 oz 4 7
  (Success) 6–8 oz 1.5–2 oz 4 7
  COMMENTS: Most effective when applied at petal fall. Apply only during late evening, night, or early morning to avoid injury to honey bees.
  (Intrepid) 2F 8-16 oz 2–4 oz 4 7
  COMMENTS: Apply at petal fall. Use allowed under a supplemental label. Do not apply more than 16 fl oz/acre/application or 64 fl oz/acre/season.
  (Dimilin) 2L 12 oz 3 oz 12 0
  COMMENTS: Include vegetable oil at the rate of 1 qt/acre. Do not apply after petal fall. Do not exceed 2 applications in any given season. Allow 21 days between applications.
** For dilute applications, rate is per 100 gal water to be applied in 300-500 gal water/acre, according to label; for concentrate applications, use 80-100 gal water/acre, or lower if the label allows.
+ 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.
Not recommended or not on label.
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/.




[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Prune
UC ANR Publication 3464
Insects and Mites
C. Pickel, UC IPM Program, Sutter/Yuba counties
F. J. A. Niederholzer, UC Cooperative Extension, Sutter/Yuba counties
W. H. Olson, UC Cooperative Extension, Butte County
F. G. Zalom, Entomology, UC Davis
R. P. Buchner, UC Cooperative Extension, Tehama County
W. H. Krueger, UC Cooperative Extension, Glenn County
Acknowledgment for contributions to Insects and Mites:
W. O. Reil, UC Cooperative Extension Solano/Yolo counties

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