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UC Pest Management Guidelines


Sporulation on the surface of a fruit infected with Monilinia fructicola.

Plum

Ripe Fruit Rot

Pathogens: mostly Monilinia fructicola and Rhizopus stolonifer

(Reviewed 5/06, updated 4/09)

In this Guideline:


SYMPTOMS AND SIGNS

Fruit in storage infected with Monilinia fructicola may develop visible decay within 24 hours at 72°F, and will produce spores in 30 hours. Decaying tissue changes from light brown to gray to black. Rotted tissue is firm and difficult to distinguish from healthy tissue.

Rhizopus stolonifer causes fruit to turn mushy and leaky in storage containers. The disease spreads rapidly from fruit to fruit. Infected tissue can be readily distinguished from healthy tissue.

COMMENTS ON THE DISEASE

Monilinia is the most common fruit decay organism. Fruit that has been injured and infected before storage provides the inoculum for the spread of Monilinia. Rhizopus produces many spores at low humidity, but in fruit packages, where humidity is high, spores are scarce and mycelia abundant.

MANAGEMENT

Fungicides are preventive, not eradicative; they must be applied to uninjured fruit before infections occur. Injured fruit cannot be protected from rot caused by Monilinia or Botrytis with the use of preharvest sprays. After harvest, Rhizopus can be controlled by storing the crop at temperatures below 40°F. Preharvest sprays for Monilinia should be applied as needed during the last 4 weeks before harvest. Where Rhizopus fruit rot is a problem, treat 10 days to 1 day before harvest.

Take a fruit sample at harvest to assess the effectiveness of current year's IPM program and to determine needs for next year's program. See FRUIT EVALUATION AT HARVEST and record your results on a monitoring form (109 KB, PDF).

Common name Amount to Use 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. When choosing a pesticide, also consider information relating to environmental quality. Not all registered pesticides are listed. Always read label of product being used.
 
PREHARVEST
A. PROPICONAZOLE
  (Orbit) 3.6 EC 4 fl oz/acre 24 0
  (Bumper) 41.8 EC 4 fl oz/acre 24 0
  MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
  COMMENTS: Most effective when applied before a rainfall and allowed to dry. Do not apply to "Stanley" type plums. Maximum of 2 preharvest sprays.
 
B. PYRIMETHANIL
  (Scala) SC 18 fl oz 12 2
  MODE OF ACTION GROUP NAME (NUMBER1): Anilinopyrimidine (9)
  COMMENTS: Do not apply more than 2 applications of Group 9 fungicides within 30 days of harvest.
 
C. CYPRODINIL
  (Vangard) WG 10 oz 12 2
  MODE OF ACTION GROUP NAME (NUMBER1): Anilinopyrimidine (9)
  COMMENTS: High summer temperatures and relative humidity reduces efficacy. Apply a maximum of 2 applications during preharvest. Do not apply more than 20 oz/acre/year.
 
D. PYRACLOSTROBIN/BOSCALID
  (Pristine) 10.5–14.5 oz/acre 12 0
  MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) and Carboxamide (7)
 
E. MYCLOBUTANIL
  (Rally) 40W 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.
 
POSTHARVEST
A. FLUDIOXONIL
  (Scholar) 50WP 8 oz/100 gal water 0 0
  MODE OF ACTION GROUP NAME (NUMBER1): Phenylpyrrole (12)
  COMMENTS: Treats 200,000 lb fruit using a spray-application system.
 
B. THIOPHANATE METHYL
  (Topsin-M) 70W 8 oz/100 gal water 12 1
  MODE OF ACTION GROUP NAME (NUMBER1): Methyl benzimidazole (1)
  COMMENT: Sporadic control may occur if fruit treated is infected with spores of benzimidazole-resistant strains of Monilinia spp. If resistance has occurred in your orchard, do not use this fungicide.
 
+ 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. 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.

IMPORTANT LINKS

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Plum
UC ANR Publication 3462
Diseases
W. D. Gubler, Plant Pathology, UC Davis
J. E. Adaskaveg, Plant Pathology, UC Riverside
K. R. Day, UC Cooperative Extension, Tulare County
Acknowledgment for contributions to Diseases:
B. L. Teviotdale, Kearney Agricultural Center, Parlier

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