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UC Pest Management Guidelines


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

Plum

Fruittree Leafroller

Scientific name: Archips argyrospila

(Reviewed 5/06, updated 4/09)

In this Guideline:


DESCRIPTION OF THE PEST

The fruittree leafroller overwinters in egg masses on scaffold limbs and twigs and emerges in spring as larvae. Larvae are dark green caterpillars with black heads. When disturbed, they wiggle backwards and drop to the ground on a silken thread. Rolled leaves webbed together to form protective nests reveal the presence of leafroller larvae. Adult moths emerge in June or July and deposit overwintering eggs. There is one generation each year.

DAMAGE

During bloom, larvae feed on leaves and buds. Later in the season they can feed on the surface of fruit, causing severe damage. Fruit often becomes infected with brown rot at feeding wounds.

MANAGEMENT

Delayed dormant treatments and bloom time applications for other pests help keep leafroller populations under control. However, regular monitoring each season is important so that prompt action can be taken if damaging populations develop. In spring, watch for the presence of fruittree leafrollers while monitoring for other pests.

Biological Control
A number of general predators, such as lacewing larvae, assassin bugs, and parasites attack fruittree leafroller larvae. These natural enemies help keep fruittree leafroller populations at low, nondamaging levels, but occasional outbreaks occur.

Organically Acceptable Methods
Fruittree leafroller can be managed organically with oil sprays during the dormant season followed by bloom treatments of Bacillus thuringiensis or the Entrust formulation of spinosad. These treatments are also used to manage other 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. If damaging populations are observed, a number of environmentally friendly chemicals are effective in controlling this pest, including Bacillus thuringiensis, spinosad (Entrust, Success), and methoxyfenozide (Intrepid).

Take a fruit damage sample at harvest to assess the effectiveness of the current year's IPM program and to determine the needs of next year's program. See FRUIT EVALUATION AT HARVEST. Record results on a monitoring form (109 KB, PDF)

Common name Amount to Use** R.E.I.+ P.H.I.+
(trade name) (conc.) (dilute) (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, impact on natural enemies and honey bees, and impact of 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.
 
DORMANT or DELAYED DORMANT
A. DORMANT OIL such as:
  DORMANT FLOWABLE EMULSION 6 gal 1.5 gal 4 0
  NARROW RANGE OIL# 4 gal 1 gal 4 0
  MODE OF ACTION: Contact including smothering and barrier effects.
  COMMENTS: Oil used alone will only provide partial control. Best when followed by an application of Bacillus thuringiensis or other environmentally sound insecticides at bloom. Oil applications at this time may cause some young shoots to burn or dieback, especially in years when trees are water-stressed, or have recently been subjected to freezing temperatures or to dry winds. Dormant flowable emulsion is less likely to cause burn. Some varieties, especially those that are weak growers or low in vigor because of soil or other location-related issues, can be especially sensitive to oil. Not all oil products are organically acceptable; be sure to check individual products.
 
BLOOM
A. BACILLUS THURINGIENSIS spp. KURSTAKI#
  (various products) Label rates 4 0
  MODE OF ACTION GROUP NUMBER1: 11.B2
  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.
 
B. SPINOSAD
  (Entrust)# 1.71–2.5 oz 0.43–0.6 oz 4 7
  (Success) 6–8 oz 1.5–2 oz 4 7
  MODE OF ACTION GROUP NUMBER1: 5
  COMMENTS: Most effective when applied at petal fall; apply only during late evening, night, or early morning to avoid injury to honey bees.
 
C. METHOXYFENOZIDE
  (Intrepid) 2F 8-16 oz 2-4 oz 4 7
  MODE OF ACTION GROUP NUMBER1: 18A
  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.
 
D. DIFLUBENZURON*
  (Dimilin) 2L 12 oz 3 oz 12 0
  MODE OF ACTION GROUP NUMBER1: 15
  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/.

IMPORTANT LINKS

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Plum
UC ANR Publication 3462
Insects and Mites
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
K. R. Day, UC Cooperative Extension, Tulare County
Acknowledgment for contributions to Insects and Mites:
R. E. Rice, Kearney Agricultural Center, Parlier

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Statewide IPM Program, Agriculture and Natural Resources, University of California
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