How to Manage Pests

UC Pest Management Guidelines

Nectarine

Scab

Pathogen: Cladosporium carpophilum

(Reviewed 6/10, updated 6/10, pesticides updated 9/15)

In this Guideline:


SYMPTOMS AND SIGNS

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, 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. Record results (PDF) for harvest sample.

Common name Amount per acre REI‡ PHI‡
(Example trade name)   (hours) (days)

UPDATED: 9/15
Calculate impact of pesticide on air quality
When choosing a pesticide, consider its usefulness in an IPM program by reviewing the pesticide’s properties, efficacy, application timing, and information relating to resistance management, honey bees (PDF), and environmental impact. Not all registered pesticides are listed. Always read the label of the product being used.
 
A. TRIFLOXYSTROBIN
  (Gem 500SC) 4–8 oz 12 1
  MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
 
B. AZOXYSTROBIN
  (Abound) 12–15.5 fl oz 4 0
  MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
  COMMENTS: Do not apply more than two applications before alternating with a fungicide that has a different mode of action group number.
 
C. FENBUCONAZOLE
  (Indar 2F) 6 oz 12 0
  MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
  COMMENTS: Do not apply more than 1 lb/acre per season.
 
D. PYRACLOSTROBIN+BOSCALID
  (Pristine) 10.5–14.5 oz 12 0
  MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) and Carboxamide (7)
  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.
 
E. CHLOROTHALONIL
  (Echo 720) 3.125–4.125 pt 12 See comments
  (Bravo Ultrex) 2.8–3.8 lb 12 See comments
  (Bravo Weather Stik) 3 1/8 – 4 1/8 pt 12 See comments
  MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M5)
  COMMENTS: Do not use with or closely following oil sprays. Do not apply after shuck split.
 
F. THIOPHANATE METHYL
  (Topsin-M 70WP) 1 1/2 lb 12 1
  MODE-OF-ACTION GROUP NAME (NUMBER1): Methyl benzimidazole (1)
 
G. CAPTAN
  (Captan 50WP) 4–8 lb 24 0
  MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M4)
  COMMENTS: Do not apply in combination with, immediately before, or closely following oil sprays.
 
H. ZIRAM
  (Ziram 76DF) 4 1/2 – 8 lb 48 30
  MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M3)
 
Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) 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.
1 Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions (for more information, see http://www.frac.info/). Fungicides with a different group number are suitable to alternate in a resistance management program. In California, make no more than one application of fungicides with mode of action Group numbers 1, 4, 9, 11, or 17 before rotating to a fungicide with a different mode of action Group number; for fungicides with other Group numbers, make no more than two consecutive applications before rotating to a fungicide with a different mode of action Group number.

IMPORTANT LINKS

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Nectarine
UC ANR Publication 3451

Diseases

J. E. Adaskaveg, Plant Pathology, UC Riverside
R. A. Duncan, UC Cooperative Extension Stanislaus County
K. R. Day, UC Cooperative Extension, Tulare County

Acknowledgment for contributions to Diseases:
B. L. Teviotdale, Kearney Agricultural Center, Parlier
W. D. Gubler, Plant Pathology, UC Davis

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