How to Manage Pests

UC Pest Management Guidelines

Almond

Anthracnose

Pathogen: Colletotrichum acutatum

(Reviewed 3/09, updated 11/12)

In this Guideline:


SYMPTOMS AND SIGNS

Symptoms of anthracnose on almond include blossom blight and fruit infections often with spur and limb dieback. Infected flowers look similar to brown rot strikes. Leaves on infected spurs develop marginal necrosis, beginning with water-soaked areas that fade in color; leaves die but remain attached to branches.

Infected nuts show round, orangish, sunken lesions on the hull. These symptoms may appear about 3 weeks after petal fall; nuts remain susceptible and can be infected later in the season if conditions are favorable. Profuse gumming occurs as the infection progresses into the kernel. Diseased fruit die and turn into mummies that remain attached to the spur. The shoots or branches that bear infected nuts often die. Although the fungus may invade fruitwood, it is seldom cultured from affected branches. Death of the wood may result from a toxin rather than from direct colonization of the wood by the fungus.

COMMENTS ON THE DISEASE

All cultivars appear to be susceptible to anthracnose. The disease has been most damaging on Thompson, Merced, Price, Peerless, Winters, Monterey, Fritz, and Butte; moderate on Harvey, Carmel, NePlus Ultra, Padre, and Mission. Nonpareil is considered to be less susceptible. Ideal conditions for the development of this disease are warm, rainy weather.

MANAGEMENT

Fungicide treatment is the most important control strategy, but must be coupled with cultural practices to achieve the best control. In orchards that have a history of anthracnose, apply fungicide sprays beginning at 5-10% bloom or pink bud and repeat every 10 to 14 days if rains persist. Late spring rains may necessitate additional applications into May. Alternate materials as follows: make the first application at pink bud using either azoxystrobin (Abound) or myclobutanil (Rally); follow this with a pyraclostrobin/boscalid (Pristine) or pyrimethanil/trifloxystrobin (Distinguish) application or a tank mix of captan or maneb mixed with iprodione or thiophanate-methyl applied at full bloom.

As long as conditions are conducive to disease development, alternate applications of azoxystrobin (Abound) or myclobutanil (Rally) with boscalid/pyraclostrobin (Pristine), pyrimethanil/trifloxystrobin (Distinguish), captan, or maneb. Pruning out dead, infected wood reduces inoculum. If sprinkler irrigation is practiced, use low angle nozzles to prevent the tree canopy from being wetted by the sprinklers as a means of reducing disease spread.

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

  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.
 
PINK BUD
 
A. TEBUCONAZOLE/TRIFLOXYSTROBIN
  (Adament) 4.0-8.0 oz 12 60
  MODE OF ACTION GROUP NAME (NUMBER1): demethylation (sterol) inhibitor (3) and Quinone outside inhibitor (11)
 
B. PROPICONAZOLE
  (Bumper/Tilt) 8.0 oz 12 60
  MODE OF ACTION GROUP NAME (NUMBER1): demethylation (sterol) inhibitor (3)
  COMMENTS: Do not make more than two successive applications, and no more than 4 per season, to limit the development of resistance.
 
C. FLUOPYRAM/TRIFLOXYSTROBIN
  (Luna Sensation) 5.0-7.6 fl oz 12 60
  MODE OF ACTION GROUP NAME (NUMBER1): succinate dehydrogenase inhibitor (7) and Quinone outside inhibitor (11)
  COMMENTS: Do not make more than two successive applications, and no more than 4 per season, to limit the development of resistance.
 
D. METCONAZOLE
  (Quash) 3.5 oz 12 25
  MODE OF ACTION GROUP NAME (NUMBER1): demethylation (sterol) inhibitor (3)
  COMMENTS: Do not make more than two successive applications, and no more than 4 per season, to limit the development of resistance.
 
E. FLUOPYRAM/TEBUCONAZOLE
  (Luna Experience) 7.2-17.0 fl oz 12 35
  MODE OF ACTION GROUP NAME (NUMBER1): succinate dehydrogenase inhibitor (7) and demethylation (sterol) inhibitor (3)
  COMMENTS: Do not make more than two successive applications and no more than 2 per season to limit the development of resistance.
 
F. AZOXYSTROBIN
  (Abound) 11–15.4 oz 4 28
  MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
  COMMENTS: Do not apply more than 2 sequential sprays before alternating with a fungicide that has a different mode of action. Do not apply more than 4 applications of strobilurin fungicides per year or apply more than 2.88 qt/product/acre/season.
 
G. AZOXYSTROBIN/DIFENOCONAZOLE
  (Quadris Top) 14 fl oz 12 28
  MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) and demethylation (sterol) inhibitor (3)
  COMMENTS: Do not make more than two successive applications, and no more than 4 per season, to limit the development of resistance.
 
H. TRIFLOXYSTROBIN
  (Gem 500 SC) 2.9-3.8 fl oz 12 60
  MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
  COMMENTS: Do not make more than two successive applications, and no more than 4 per season, to limit the development of resistance.
 
I. CHLOROTHALONIL
  (various) Label rates See label See label
  MODE OF ACTION GROUP NAME (NUMBER1): Chlorinated hydrocarbon (M5)
  COMMENTS: Use as a multi-site protective treatment with long residual.
 
BLOOM AND AFTER (AS LONG AS WEATHER CONDUCIVE)
A. TEBUCONAZOLE/TRIFLOXYSTROBIN
  (Adament) 4.0-8.0 oz 12 60
  MODE OF ACTION GROUP NAME (NUMBER1): demethylation (sterol) inhibitor (3), Quinone outside inhibitor (11)
  COMMENTS: Do not make more than two successive applications, and no more than 4 per season, to limit the development of resistance.
 
B. PROPICONAZOLE
  (Bumper/Tilt) 8.0 oz 12 60
  MODE OF ACTION GROUP NAME (NUMBER1): demethylation (sterol) inhibitor (3)
  COMMENTS: Do not make more than two successive applications, and no more than 4 per season, to limit the development of resistance
 
C. FLUOPYRAM/TRIFLOXYSTROBIN
  (Luna Sensation) 5.0-7.6 fl oz 12 60
  MODE OF ACTION GROUP NAME (NUMBER1): succinate dehydrogenase inhibitor (7), Quinone outside inhibitor (11)
  COMMENTS: Do not make more than two applications per season of QoIs or SDHIs to limit the potential for the development of resistance
 
D. METCONAZOLE
  (Quash) 3.5 oz 12 25
  MODE OF ACTION GROUP NAME (NUMBER1): demethylation (sterol) inhibitor (3)
  COMMENTS: Do not make more than two successive applications, and no more than 4 per season, to limit the development of resistance
 
E. FLUOPYRAM/TEBUCONAZOLE
  (Luna Experience) 7.2-17.0 fl oz 12 35
  MODE OF ACTION GROUP NAME (NUMBER1): succinate dehydrogenase inhibitor (7) and demethylation (sterol) inhibitor (3)
  COMMENTS: Do not make more than two successive applications and no more than 2 per season to limit the development of resistance
 
F. AZOXYSTROBIN/PROPICONAZOLE
  (Quilt Xcel) 17.5-26.0 fl oz 12 60
  MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) and demethylation (sterol) inhibitor (3)
  COMMENTS: Do not make more than two applications per season of QoIs or SDHIs to limit the potential for the development of resistance.
 
G. TRIFLOXYSTROBIN
  (Gem 500 SC) 2.9-3.8 fl oz 12 60
  MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11)
  COMMENTS: Do not make more than two applications per season of QoIs or SDHIs to limit the potential for the development of resistance
 
H. PYRACLOSTROBIN/BOSCALID
  (Pristine) 10.5–14.5 oz 12 25
  MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) and succinate dehydrogenase inhibitor (7)
  COMMENTS: Do not make more than one application per season of QoIs or SDHIs to limit the potential for the development of resistance.
 
I. CAPTAN
  (various) Label rates See label See label
  MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M4)
 
J. ZIRAM
  (Ziram 76DF) 6-8 lbs 24 0
  MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M3)
  COMMENTS: Do not apply more than 32 lb of product/acre/season.
 
K. THIOPHANATE-METHYL
  (Topsin-M) 1.0-1.5 lbs See label See label
  MODE OF ACTION GROUP NAME (NUMBER1): methyl benzimidazole (1)
  COMMENTS: Do not apply more than 3 lb product per year. Some populations of the pathogen are not sensitive to MBC fungicides on almond in California.
 
+ 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 these two intervals is the minimum time that must elapse before harvest may occur.
1 Group numbers are assigned by the Fungicide Resistance Action Committee (FRAC) according to different modes of actions (For information, see 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 fungicide with a different mode of action Group number.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Almond
UC ANR Publication 3431

Diseases

J. E. Adaskaveg, Plant Pathology, UC Riverside
W. D. Gubler, Plant Pathology, UC Davis
Roger Duncan, UC Cooperative Extension, Stanislaus County
J. J. Stapleton, UC IPM Program, Kearney Agricultural Center, Parlier
B. A. Holtz, UC Cooperative Extension, San Joaquin County

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