How to Manage Pests

UC Pest Management Guidelines

Almond

Green Fruit Rot (Jacket Rot)

Pathogens: Botrytis cinerea, Sclerotinia sclerotiorum, Monilinia laxa

(Reviewed 3/09, updated 11/12)

In this Guideline:


SYMPTOMS AND SIGNS

Green fruit rot begins during the latter part of the bloom period when the fungus infects senescing petals and anthers. Infected petals develop water-soaked brown spots. Some infected petals may fall onto leaves causing secondary infections. Anther infections can spread to floral tubes or flower jackets causing them to wither and stick to developing fruit. As fruit sets and starts to grow, a brown spot develops where the jacket sticks to it. This is particularly a problem where nut clusters trap senescing flower parts. Frequently this leads to rot of entire nut clusters.

COMMENTS ON THE DISEASE

This disease is of little importance in many years, but when conditions are cool and wet during bloom, it can cause severe losses. One or more of several pathogens may be involved.

MANAGEMENT

When bloom is extended and moisture is abundant, apply a fungicide at full bloom to prevent green fruit rot. Continue treatment until rain stops. Be sure the fungicide you choose is effective against all three potential pathogens; demethylation (sterol) inhibitor fungicides such as myclobutanil (Laredo) and propiconazole (Orbit) are not effective against Botrytis cinerea.

Common name Amount/Acre R.E.I.+ P.H.I.+
(example 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.
 
A. DIFENOCONAZOLE/CYPRODINIL
  (Inspire Super) 10.0-12.0 fl oz 12 60
  MODE OF ACTION GROUP NAME (NUMBER1): demethylation (sterol) inhibitor (3) and anilinopyrimidine (9)
  COMMENTS: Do not make more than two successive applications, and no more than 4 per season, to limit the development of resistance.
 
B. 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.
 
C. 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 4 applications per season of QoIs or SDHIs to limit the potential for the development of resistance.
 
D. IPRODIONE
  (Rovral 4F) 1 pt 24 0
  MODE OF ACTION GROUP NAME (NUMBER1): Dicarboximide (2)
  COMMENTS: Addition of a narrow range oil (superior, supreme) at 1 to 2% volume/volume increases the effectiveness of this material. Do not apply oil, however, within 3 weeks of a sulfur application or closely before or after an application of captan or chlorothalonil. Do not apply more than 4 applications/season.
 
E. PYRIMETHANIL
  (Scala SC) 9–18 fl oz 12 30
  MODE OF ACTION GROUP NAME (NUMBER1): Anilinopyrimidine (9)
 
F. THIOPHANATE-METHYL
  (Topsin M 70WP) 1.5–2 lb 3 days 1
  MODE OF ACTION GROUP NAME (NUMBER1): Methyl benzimidazole (1)
  COMMENTS: Strains of brown rot pathogen resistant to thiophanate-methyl have been found on almond, but resistance is not widespread. Do not apply more than 3 lb/season/acre.
 
G. CYPRODINIL
  (Vangard WG) 5 oz 12 60
  MODE OF ACTION GROUP NAME (NUMBER1): Anilinopyrimidine (9)
  COMMENTS: Do not apply more than 30 oz/acre/crop/year.
 
H. FENHEXAMID
  (Elevate) 1.5 lb 12 see comments
  MODE OF ACTION GROUP NAME (NUMBER1): Hydroxyanilide (17)
  COMMENTS: Apply up to 28 days after petal fall.
 
I. CAPTAN
  (various 50WP) Label rates See label See label
  MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M4)
  COMMENTS: Preharvest interval varies depending on formulation and if hulls are to be fed to livestock. Do not apply in combination with, immediately before, or closely following oil sprays.
 
+ 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 more 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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