How to Manage Pests

UC Pest Management Guidelines

Apricot

Brown Rot Blossom and Twig Blight

Pathogens: Monilinia laxa and Monilinia fructicola

(Reviewed 10/14, updated 10/14)

In this Guideline:


SYMPTOMS AND SIGNS

The blossom and twig blight phase begins with the death of young blossoms and their associated spurs and leaves. Infection moves from flowers into twigs to form small cankers. Gum exudes at the base of infected flowers. Cankers on blighted twigs have tan centers with dark margins. In high humidity gray brown spore masses form on diseased flower parts and twig cankers.

COMMENTS ON THE DISEASE

The fungus survives on diseased twigs and mummified fruits, either on the tree or on the ground. Brown rot fungus spores are airborne and are also spread by rain splash and insects. Moderate temperatures and moist weather during bloom favor blossom blight.

MANAGEMENT

  • Remove fruit mummies from the trees immediately after harvest or during the dormant season.
  • Use soil cultivation to cover and breakup mummified fruit.
  • Two to three bloom fungicide applications are necessary to control brown rot blossom and twig blight, depending on the weather. Because apricot sepals, in addition to other flower parts, are susceptible, the application at red bud is most important.
  • Spray every 14 days to provide adequate continuing protection,. When continued heavy rainfall is occurring or other conditions are occurring that result in high susceptibility to infection, shorten this interval to 7 to 10 days.

Aerial applications are generally not as effective as properly applied ground sprays but may be necessary when the orchard floor is too wet.

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. PROPICONAZOLE
  (Bumper ES, Tilt) 4 fl oz 12 0
  MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
  COMMENTS: Apply at red bud.
 
B. TEBUCONAZOLE
  (Tebucon 45DF, Toledo) 4–8 oz 120 0
  MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
  COMMENTS: Toledo use allowed under a Supplemental Label.
 
C. FENBUCONAZOLE
  (Indar 2F) 6 fl oz 12 0
  MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
  COMMENTS: Apply a minimum of 50 gal water/acre. A protectant fungicide. Begin applications before infections occur if conditions are conducive to disease development.
 
D. DIFENOCONAZOLE / CYPRODINIL
  (Inspire Super) 16–20 fl oz 12 2
  MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3) and Anilinopyrimidine (9)
  COMMENTS: For brown rot blossom blight, apply at early bloom and again at full bloom. For brown rot on fruit apply as needed, but not more than twice during preharvest with a minimum of 7 days between treatments.
 
E. METCONAZOLE
  (Quash) 2.5–3.5 oz 12 14
  MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
 
F. 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: To reduce the potential for the development of resistance, do not make more than two consecutive applications or more than four applications per season of Pristine or other quinone outside inhibitor (11) or succinate dehydrogenase inhibitor (7) fungicides.
 
G. 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.
 
H. AZOXYSTROBIN / DIFENOCONAZOLE
  (Quadris Top) 12–14 fl oz 12 0
  MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3) and Quinone outside inhibitor (11)
 
I. AZOXYSTROBIN / PROPICONAZOLE
  (QuiltXcel) Label rates 12 0
  MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) and Demethylation inhibitor (3)
 
J. PYRIMETHANIL      
  (Scala SC) 9–18 fl oz 12 2
  MODE-OF-ACTION GROUP NAME (NUMBER1): Anilinopyrimidine (9)
 
K. THIOPHANATE METHYL
  (Topsin-M 70WP) 0.5 lb/100 gal water up to 1.5 lb/acre 48 (2 days) 1
  MODE-OF-ACTION GROUP NAME (NUMBER1): Methyl benzimidazole carbamate (1)
  COMMENTS: Only one application per year. If this material is used during bloom, do not use later for control of powdery mildew or ripe fruit rot. Check with your processor before using this material. Because strains of M. fructicola that are resistant to thiophanate methyl have been found in California, only one of the three bloom applications (preferably the one at red bud) should be thiophanate methyl. If resistance has occurred in your orchard, do not use this fungicide.
 
L. CYPRODINIL
  (Vangard WG) 5 oz 12 2
  MODE-OF-ACTION GROUP NAME (NUMBER1): Anilinopyrimidine (9)
 
M. 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 inhibitor fungicide.
 
N. 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.
 
O. IPRODIONE
  (Rovral 4, Nevado, Iprodione) 1–2 pt 24 NA
  MODE-OF-ACTION GROUP NAME (NUMBER1): Dicarboximide (2)
  COMMENTS: Addition of a narrow range oil (Superior, Supreme) at 1–2% increases the effectiveness of this material. Do not use after petal fall. Iprodione is highly toxic to bees. Do not spray directly or allow to drift onto blooming crops or weeds where bees are foraging.
 
P. 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 and avoid making more than two consecutive applications with this material.
 
Q. 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 sequential sprays before alternating with a fungicide that has a different mode of action. Do not apply more than 1 lb a.i./acre per season.
 
R. DICLORAN
  (Botran 75-W) Label rates 12 10
  MODE-OF-ACTION GROUP NAME (NUMBER1): Aromatic hydrocarbon (14)
  COMMENTS:
 
S. CAPTAN 50WP
  (Various) 3–5 lb 24 0
  MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M4)
  COMMENTS: Do not use captan with or closely following oil sprays. Check with your processor before using this material. Do not apply after 75% petal fall.
 
T. CHLOROTHALONIL
  (Echo 720) 3.125–4.125 pt 12 NA
  (Bravo Ultrex) 2.8–3.8 lb 12 NA
  (Bravo Weather Stik) 3.125–4.125 pt 12 NA
  MODE-OF-ACTION GROUP NAME (NUMBER1): Multi-site contact (M5)
  COMMENTS: May cause an allergic skin reaction in some people. Do not use with or closely following oil sprays. Do not apply after jacket (shuck) split. Do not apply more than 20.5 pint Bravo Weather Stik/acre per season. Do not apply more than 18.8 lb Bravo Ultrex/acre per season.
 
U. TRIFLOXYSTROBIN
  (Gem 500SC) 1.9–3.8 fl oz 12 1
  MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
 
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.
NA Not applicable.
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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