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How to Manage Pests

UC Pest Management Guidelines


Obliquebanded leafroller larva and shallow feeding injury in surface of ripe apricot.

Apricot

Obliquebanded Leafroller

Scientific name: Choristoneura rosaceana

(Reviewed 11/07, updated 2/09)

In this Guideline:


DESCRIPTION OF THE PEST

Obliquebanded leafroller overwinter as third instar larvae under loose scales or pieces of bark. The overwintered larvae pupate in spring and the first generation of adults emerges in late March or April. Larvae are yellowish green with brown to black heads. As they mature, larvae construct tubular shelters from a single leaf. Adults are reddish brown moths with dark brown bands on the wings. There are two or three generations a year in the Central Valley; it is rarely found in Central Coast orchards.

DAMAGE

Infestations of obliquebanded leafroller can occasionally reach damaging levels in apricots. Larvae feed on flower parts and on fruit early in the season, causing deep depressions that eventually become rough and russeted by harvest.

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.

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
Biological control is acceptable for use on organically grown apricots as are delayed-dormant oil sprays combined with the Entrust formulation of spinosad, bloom sprays of Bacillus thuringiensis, and springtime sprays of Entrust.

Monitoring and Treatment Decisions
Check the orchard in early spring for the presence of larvae and rolled leaves. The best timing for control of overwintering larvae is at full bloom or early petal fall. Fruit harvested before June 15 will not need additional treatments. Fruit harvested after June 15 will need to be monitored for the summer generation.

Place pheromone traps in the orchard of late-maturing varieties in mid- to late April to determine when to make a summer treatment. Using a lower threshold of 43°F and an upper of 85°F, begin accumulating degree-days when the first moths are trapped (generally late April in the southern San Joaquin Valley to May in the central San Joaquin Valley). For assistance in calculating degree-days, see "Degree-days ".

Monitor fruit and leaves for caterpillars when about 500 degree-days have accumulated. Currently there are no treatment thresholds. If a decision is made to treat, make an application at 600-700 degree-days from the biofix (i.e., when the first moths were trapped).

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 SAMPLING AT HARVEST). Record results (sample form115 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 in to 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.
 
BLOOM
A. BACILLUS THURINGIENSIS ssp. KURSTAKI#
  (various products) Label rates 4 0
  MODE OF ACTION GROUP NUMBER1: 11.B2
  COMMENTS: Least harmful to beneficials. Bt is a stomach poison and must be consumed by the leafroller; therefore it is most effective when applied during warm, dry weather when larvae are actively feeding. Most effective against young larvae. Requires more than 1 treatment; apply second application 7–10 days after first.
 
PETAL FALL and AFTER
A. SPINOSAD
  (Entrust)# 1.71–2.5 oz 0.43–0.6 oz 4 14
  (Success) 6–8 fl oz 1.5–2 fl oz 4 14
  MODE OF ACTION GROUP NUMBER1: 5
  COMMENTS: Most effective when applied at petal fall. This product is toxic to bees for 3 hours following treatment; apply in the late evening after bees have stopped foraging. Do not apply more than 29 fl oz/acre/year of Success or 9 oz/acre/year of Entrust.
 
B. SPINETORAM
  (Delegate WG) 4.5–7 oz 1.125–1.75 oz 4 14
  MODE OF ACTION GROUP NUMBER1: 5
  COMMENTS: This product is toxic to bees for 3 hours following treatment; apply in the late evening after bees have stopped foraging. Do not apply more than 28 oz/acre/year or make more than 4 applications/year.
 
C. CHLORANTRANILIPROLE
  (Altacor) 35WDG 3–4.5 oz 0.75–1.125 oz 4 10
  MODE OF ACTION GROUP NUMBER1: 28
  COMMENTS: Do not apply more than 9 oz/acre/year or make more than 4 applications a year. Do not apply with less than 100 or more than 200 gallons water/acre.
 
D. METHOXYFENOZIDE
  (Intrepid) 2F 8–16 fl oz 2–4 fl oz 4 7
  MODE OF ACTION GROUP NUMBER1: 18A
  COMMENTS: Do not apply more than 16 fl oz/acre/application or more than 64 fl oz/acre/season.
 
E. PHOSMET
  (Imidan) 70WP 4.25 lb 1 lb 3 days 14
  MODE OF ACTION GROUP NUMBER1: 1B
 
F. DIAZINON* 50WP 3 lb 1 lb 24 21
  MODE OF ACTION GROUP NUMBER1: 1B
  COMMENTS: Avoid drift and tailwater runoff into surface waters. Where apricots are grown adjacent to waterways, do not use this material.
 
** For concentrate applications, use the amount given in 80-100 gal water/acre or lower if the label allows; for dilute application, amount is per 100 gal water to be applied in 300-400 gal water/acre, according to label.
+ 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 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: Apricot
UC ANR Publication 3433
Insects and Mites
W. W. Coates, UC Cooperative Extension, San Benito County
R. A. Van Steenwyk, Insect Biology, UC Berkeley
W. J. Bentley, UC IPM Program, Kearney Agricultural Center, Parlier
K. R. Day, UC Cooperative Extension, Tulare County
K. A. Kelley, UC Cooperative Extension, Stanislaus County
J. L. Caprile, UC Cooperative Extension, Contra Costa County
Acknowledgment for contributions to Insects and Mites:
L. C. Hendricks, UC Cooperative Extension, Merced County

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