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UC Pest Management Guidelines


Ripe apricot fruit with powdery mildew, caused by Sphaerotheca pannosa.

Apricot

Powdery Mildew

Pathogens: Sphaerotheca pannosa and Podosphaera tridactyla

(Reviewed 11/07, updated 11/07)

In this Guideline:


SYMPTOMS AND SIGNS

Powdery mildew appears as weblike white growth on fruit, leaves, and stems. Older lesions on fruit are scabby.

COMMENTS ON THE DISEASE

Sphaerotheca pannosa causes mildew on fruit and leaves in spring; Podosphaera tridactyla attacks leaves in summer and fall. Sphaerotheca pannosa does not overwinter on apricot; primary inoculum comes from infected roses in spring. Remove nearby roses to reduce sources of inoculum.

MANAGEMENT

Treat during bloom and fruit development as needed; early applications are most effective.

Common name Amount/Acre R.E.I.+ P.H.I.+
(trade name)   (hours) (days)

  Calculate impact of pesticide on air quality
The following materials are listed in order of usefulness in an IPM program, taking into account efficacy. Also consider the general properties of the fungicide as well as information relating to environmental impact. Not all registered pesticides are listed. Always read label of product being used.
 
Caution: Never apply sulfur to apricot trees or captan to apricot fruit.
 
A. THIOPHANATE METHYL
  (Topsin M) 70W 1.5 lb 12 1
  MODE OF ACTION GROUP NAME (NUMBER1): Methyl benzimidazole (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.
 
B. PYRACLOSTROBIN/BOSCALID
  (Pristine) 10.5–14.5 oz 12 0
  MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) and Carboxamide (7)
 
C. MYCLOBUTANIL
  (Rally) 40WP 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/season.
 
D. PROPICONAZOLE
  (Bumper, Orbit) 4 fl oz 24 0
  MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
  COMMENTS: Apply at red bud.
 
E. 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/season.
 
 
Restricted entry interval (R.E.I.) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (P.H.I.) 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, 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
Acknowledgment for contributions to Diseases:
B. L. Teviotdale, Kearney Agricultural Center, Parlier

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