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How to Manage Pests

UC Pest Management Guidelines

| More pests | More crops | About guidelines |

Russet scab on developing prunes.

Prune

Russet Scab

(Reviewed 6/06, updated 6/06)

In this Guideline:

SYMPTOMS

Russet scab, also known as lacey scab, is a physiological disorder that causes a superficial russeting of fruit; most prevalent on stylar end.

COMMENTS ON THE DISEASE

Russet scab develops in years of excessive rain during and soon after bloom. Research has shown that prunes with 75% scab are not contributing to off grade.

MANAGEMENT

Treat just before or at full bloom in fresh market prunes.

Common name Amount to Use
(trade name)  
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. CAPTAN 50WP 6 lb
  (various products)  
  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.
 
B. CHLOROTHALONIL
  (Bravo Weather Stik) 3.125–5.5 pt
  (Echo 720) 3.125-4.125 pt
  MODE OF ACTION: A multi-site contact (Group M5)1 chloronitrile fungicide.
  COMMENTS: Use higher rate on trees taller than 20 ft and lower rate on smaller trees. Do not use with or closely following oil sprays.
 
 
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 prune fungicides

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Prune
UC ANR Publication 3464
Diseases
W. D. Gubler, Plant Pathology, UC Davis
J. E. Adaskaveg, Plant Pathology, UC Riverside
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. J. A. Niederholzer, UC Cooperative Extension, Sutter/Yuba counties
Acknowledgment for contributions to the diseases section:
B. L. Teviotdale, Kearney Agricultural Center, Parlier

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