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How to Manage Pests

UC Pest Management Guidelines


Scab lesions on peach fruit.

Nectarine

Scab

Pathogen: Cladosporium carpophilum

(Reviewed 6/06, updated 6/06)

In this Guideline:


SYMPTOMS

Scab affects foliage, young shoots, and fruit, but damage is the result of fruit infections. Fruit infections appear as dark lesions on ripening fruit, most commonly on the upper surface, and may grow together to form large blotches. Lesions may have green or yellowish blotches that turn grayish when spores are produced.

COMMENTS ON THE DISEASE

Primarily a problem on nectarines in the northern San Joaquin Valley during wet spring weather. The fungus that causes scab overwinters in lesions on first-year twigs. Spores are produce in these lesions when humidity exceeds 70% beginning at bloom and lasting several weeks. Spores are spread by air movement and splashing water and will infect developing fruit, although it may take several weeks for lesions to appear.

MANAGEMENT

In orchards with a history of scab, applications of a fungicide within 3 weeks after full bloom to protect developing fruit, and again at 5 weeks if disease was severe the previous year, will reduce fruit infection. Fungicides applied during bloom for brown rot and at petal fall to control shot hole will also reduce the spread of scab if appropriate fungicides are chosen.

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) and record results on a monitoring form (100KB, PDF).

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

The following materials are listed in order of usefulness in an IPM program, taking into account efficacy. When choosing a pesticide, also consider information relating to environmental impact.
 
A. AZOXYSTROBIN
  (Abound) 12.3–15.4 fl oz/acre 0
  MODE OF ACTION: A Qol (Group 11)1 fungicide.
  COMMENTS: Do not apply more than two applications before alternating with a fungicide that has a different Group number.
 
B. FENBUCONAZOLE
  (Indar) 75WSP 2 oz/acre  
  MODE OF ACTION: A DMI (Group 3)1 triazole fungicide.
  COMMENTS: Do not apply more than 1 lb/acre/season.
 
C. PYRACLOSTROBIN/BOSCALID
  (Pristine) 10.5–14.5 oz/acre  
  MODE OF ACTION: A Qol (Group 11)1 and carboxamide (Group 7)1 fungicide.
  COMMENTS: To reduce the potential for resistance, do not make more than 5 applications of this or other Group 11 or 7 fungicides per season. Do not make more than 2 sequential applications of this product.
 
D. THIOPHANATE METHYL
  (Topsin-M) 70WP 8 oz/100 gal water 1
  MODE OF ACTION: A MBC (Group 1)1 thiophanate fungicide.
 
E. CAPTAN 50WP
  (various products) 2 lb/100 gal water (dilute spray)  
  MODE OF ACTION: A multi-site contact (Group M4)1 phthalimide fungicide.
  COMMENTS: Do not apply in combination with, immediately before, or closely following oil sprays.
 
F. ZIRAM 76DF 2–2.5 lb/100 gal water (dilute spray)  
  MODE OF ACTION: A multi-site contact (Group M3)1 dithiocarbamate fungicide.
 
 
Preharvest interval. Do not apply within this many days of harvest.
1 Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions. Fungicides with a different Group number are suitable to alternate in a resistance management program. For more information, see http://www.frac.info/.

More information on nectarine fungicides

PDF: You need a PDF reader, such as Acrobat Reader version 8 or later, to view or print this PDF. If no reader is installed on your computer, you can download a free copy of Adobe Acrobat Reader.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Nectarine
UC ANR Publication 3451
Diseases
W. D. Gubler, Plant Pathology, UC Davis
J. E. Adaskaveg, Plant Pathology, UC Riverside
Acknowledgment for contributions to the diseases section:
B. L. Teviotdale, Kearney Agricultural Center, Parlier

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Statewide IPM Program, Agriculture and Natural Resources, University of California
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For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See How to manage pests, or in the U.S., contact your local Cooperative Extension office for assistance. /PMG/r540101511.html revised: June 15, 2006. Contact webmaster.