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How to Manage Pests

UC Pest Management Guidelines


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

Nectarine

Obliquebanded Leafroller

Scientific Name: Choristoneura rosaceana

(Reviewed 6/06, updated 6/06)

In this Guideline:


DESCRIPTION OF THE PEST

Obliquebanded leafroller overwinter as third-instar larvae under bud scales. The overwintered larvae pupate in spring, and the first generation of adults emerges in late April or May. 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 usually two generations a year in the Sacramento Valley and up to three in the San Joaquin Valley.

DAMAGE

Infestations of obliquebanded leafroller can occasionally reach damaging levels in nectarines. Larvae feed on flower parts and on fruit early in the season, causing deep depressions that eventually become rough and russeted by harvest. Because of the high cyanide content of nectarine leaves, larvae generally concentrate their feeding on fruit; consequently, lower numbers of larvae may cause more damage in nectarines than in other crops. This leafroller is more damaging than fruittree leafrollers because it has one to two summer generations.

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. Throughout the season, watch for the presence of leafrollers while monitoring for other pests. This is especially important in orchards where bloom time sprays and pheromone confusion are used to control peach twig borer and oriental fruit moth.

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
Organically acceptable management tools include biological control and sprays of Bacillus thuringiensis or the Entrust formulation of spinosad.

Monitoring and Treatment Decisions    Degree-day calculator    Degree-day table
Check the orchard in early spring (March–April) for the presence of larvae and feeding damage on flowers (see EARLY SEASON MONITORING). If damaging populations are observed, a number of environmentally friendly insecticides are effective in controlling this pest, including Bacillus thuringiensis, spinosad (Entrust, Success), and methoxyfenozide (Intrepid). The best timing for control of overwintering larvae is at full bloom or early petal fall.

Pheromone traps placed in the orchard in mid-April (see PHEROMONE TRAPS) will help to monitor the population levels of this insect and provide information for management of the summer generations. Based on research done in California pistachio orchards, begin accumulating degree-days as soon as traps begin to catch moths using a lower threshold of 43°F and an upper threshold of 94°F. (For assistance in calculating degree-days, see "Degree-days ".). Make treatments between 600 and 1000 DD.

Also, fruit samples taken every other week after color break (see PREHARVEST FRUIT SAMPLES) will help detect damage from this pest, and a fruit damage sample at harvest will help 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 monitoring forms for preharvest (100KB, PDF) and harvest (100KB, PDF) samples.

Common name Amount to Use** P.H.I.+
(trade name) (conc.) (dilute) (days)

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.
 
DELAYED DORMANT
A. NARROW RANGE OIL
  (Superior, Supreme) 4–8 gal 1.5–2 gal  
  MODE OF ACTION: Contact including smothering and barrier effects.
  . . . PLUS . . .
  SPINOSAD
  (Entrust)# 1.25–2.5 oz 0.3–0.6 oz  
  (Success) 4–8 oz 1–2 oz  
  MODE OF ACTION: A microbial (Group 5)1 insecticide.
 
BLOOM
A. BACILLUS THURINGIENSIS ssp. KURSTAKI#
  (various products) Label rates 0
  MODE OF ACTION: A microbial (Group 11.B2)1 insecticide.
  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.
 
B. SPINOSAD
  (Entrust)# 1.71–2.5 oz 0.43–0.6 oz 14
  (Success) 6–8 oz 1.5–2 oz 14
  MODE OF ACTION: A microbial (Group 5)1 insecticide.
  COMMENTS: Most affective 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 oz/acre/year of Success or 9 oz/acre/year of Entrust.
 
C. METHOXYFENOZIDE
  (Intrepid) 2F 8-16 oz 2-4 oz  
  MODE OF ACTION: An insect growth regulator (Group 18)1 insecticide.
  COMMENTS: Apply at petal fall. Do not apply more than 16 fl oz/acre/application or 64 fl oz/acre/season.
 
D. DIFLUBENZURON*
  (Dimilin) 2L 12 oz 3 oz  
  MODE OF ACTION: An insect growth regulator (Group 15)1 insecticide.
  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.
 
AFTER BLOOM
A. BACILLUS THURINGIENSIS ssp. KURSTAKI#
  (various products) Label rates 0
  MODE OF ACTION: A microbial (Group 11.B2)1 insecticide.
  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.
 
B. SPINOSAD
  (Entrust)# 1.71–2.5 oz 0.43–0.6 oz 14
  (Success) 6–8 oz 1.5–2 oz 14
  MODE OF ACTION: A microbial (Group 5)1 insecticide.
  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 29 oz/acre/year of Success or 9 oz/acre/year of Entrust.
 
C. METHOXYFENOZIDE
  (Intrepid) 2F 8-16 oz 2-4 oz  
  MODE OF ACTION: An insect growth regulator (Group 18)1 insecticide.
  COMMENTS: Do not apply more than 16 fl oz/acre/application or 64 fl oz/acre/season.
 
D. CARBARYL*
  (Sevin) 80S 5 lb 1.25 lb 1
  MODE OF ACTION: A carbamate (Group 1A)1 insecticide.
  COMMENTS: May cause increased spider mite problems; best used late in the season. Do not apply more than 7.5 lb/acre/season.
 
E. PHOSMET
  (Imidan) 70WP 4.25 lb 1 lb 14
  MODE OF ACTION: An organophosphate (Group 1B)1 insecticide.
 
 
**  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 label allows.
+ Preharvest interval. Do not apply within this many days of 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 Modes of action are important in preventing the development of resistance to pesticides. 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. 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 is assigned by IRAC (Insecticide Resistance Action Committee). For additional information, see their Web site at http://www.irac-online.org/.

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[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Nectarine
UC ANR Publication 3451
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 the insects and mites section:
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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