How to Manage Pests

UC Pest Management Guidelines

Apricot

Powdery Mildew

Pathogens: Sphaerotheca pannosa and Podosphaera tridactyla

(Reviewed 10/14, updated 10/14)

In this Guideline:


SYMPTOMS AND SIGNS

Powdery mildew appears as weblike white growth on fruit, leaves, and stems. Older lesions on fruit are scabby and form red or purple splotches.

COMMENTS ON THE DISEASE

Sphaerotheca pannosa causes mildew on fruit and leaves in the spring; Podosphaera tridactyla attacks leaves in the summer and fall. Sphaerotheca pannosa does not overwinter on apricot. The primary inoculum originates most likely from infected roses in spring.

MANAGEMENT

Remove nearby roses to reduce sources of inoculum.

Begin applications at full bloom and treat through fruit development as needed; early applications are most effective. Fruit becomes resistant to new infections after pit-hardening, but previous infections may still be active.

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

UPDATED: 10/14
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, and environmental impact. Not all registered pesticides are listed. Always read the label of the product being used.
 
Caution: Never apply sulfur to apricot trees or captan to apricot fruit.
 
A. PENTHIOPYRAD
  (Fontelis) 14–20 fl oz 12 0
  MODE-OF-ACTION GROUP NAME (NUMBER1): Succinate dehydrogenase inhibitors (7)
  COMMENTS: Resistance warning: do not make more than two consecutive applications and no more than 61 fl oz/acre per year of Fontelis or other succinate dehydrogenase inhibitors fungicide.
 
B. QUINOXYFEN
  (Quintec) 7 fl oz 12 7
  MODE-OF-ACTION GROUP NAME (NUMBER1): Quinoline (13)
  COMMENTS: Use allowed under a Supplemental Label.
 
C. PYRACLOSTROBIN / FLUXAPYRAXAD
  (Merivon) 4–6.7 fl oz 12 0
  MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) and Succinate dehydrogenase inhibitors (7)

COMMENTS: To reduce the potential for the development of resistance, do not make more than two consecutive applications or more than four applications or 20.1 fl oz per season of Merivon or other quinone outside inhibitor (11) or succinate dehydrogenase inhibitor (7) fungicides.

 
D. TEBUCONAZOLE / TRIFLOXYSTROBIN
  (Adament 50WG) 4–8 oz 5 days 1
  MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3), Quinone outside inhibitor (11)
  COMMENTS: Use allowed under a Supplemental Label.
 
E. PROPICONAZOLE
  (Bumper ES, Tilt) 4 fl oz 12 0
  MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
  COMMENTS: Begin applications at full bloom.
 
F. DIFENOCONAZOLE / CYPRODINIL
  (Inspire Super) 16–20 fl oz 12 2
  MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3), Anilinopyrimidine (9)
  COMMENTS: Begin applications at full bloom, but do not apply more than twice during preharvest with a minimum of 7 days between treatments.
 
G. METCONAZOLE
  (Quash) 3.5–4.0 oz 12 14
  MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
  COMMENTS: Begin applications at full bloom.
 
H. PYRACLOSTROBIN / BOSCALID
  (Pristine) 10.5–14.5 oz 12 0
  MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) and Succinate dehydrogenase inhibitors (7)
  COMMENTS: Begin applications at full bloom.
 
I. DIFENOCONAZOLE / AZOXYSTROBIN
  (Quadris Top) 12–14 fl oz 12 0
  MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3), Quinone outside inhibitor (11)
  COMMENTS: Begin applications at full bloom, but do not apply more than twice during preharvest with a minimum of 7 days between treatments.
 
J. AZOXYSTROBIN / PROPICONAZOLE
  (QuiltXcel) Label rates 12 0
  MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3), Quinone outside inhibitor (11)
  COMMENTS: Begin applications at full bloom, but do not apply more than twice during preharvest with a minimum of 7 days between treatments.
 
K. THIOPHANATE METHYL
  (Topsin M 70W) 1.5 lb 2 days 1
  MODE-OF-ACTION GROUP NAME (NUMBER1): Methyl benzimidazole carbamate (1)
  COMMENTS: Use only once a year. Do not use in orchards where resistance has been observed. Use only in combination or in an alternating application program with a different mode-of-action group number. For tank mixes, observe all directions for use on all labels, and employ the most restrictive limits and precautions. Never exceed the maximum a.i. on any label when tank mixing products that contain the same a.i.
 
L. MYCLOBUTANIL
  (Rally 40WSP) 2.5–6 oz 24 0
  MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
  COMMENTS: Do not apply more than 2.75 lb/acre per season.
 
M. FENHEXAMID
  (Elevate 50WDG) 1–1.5 lb 12 0
  MODE-OF-ACTION GROUP NAME (NUMBER1): Hydroxyanilide (17)
  COMMENTS: Do not apply more than 6 lb/acre per season.
 
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. For fungicides with mode-of-action group numbers 1, 4, 7, 9, 11, or 17, make no more than one application 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 fungicide with a different mode-of-action group number.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Apricot
UC ANR Publication 3433

Diseases

J. E. Adaskaveg, Plant Pathology, UC Riverside
W. D. Gubler, Plant Pathology, UC Davis
W. W. Coates, UC Cooperative Extension, San Benito County
J. J. Stapleton, UC IPM Program, Kearney Agricultural Center, Parlier
J. L. Caprile, UC Cooperative Extension, Contra Costa County
B. A. Holtz, UC Cooperative Extension, Madera County
K. M. Kelley Anderson, UC Cooperative Extension, Stanislaus County

Acknowledgment for contributions to Diseases:
B. L. Teviotdale, Kearney Agricultural Center, Parlier

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