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UC Pest Management Guidelines


Ripe fruit rot caused by Monilinia.

Nectarine

Ripe Fruit Rot

Pathogens: Monilinia fructicola, Botrytis cinerea, Rhizopus spp.

(Reviewed 6/10, updated 6/10)

In this Guideline:


SYMPTOMS AND SIGNS

Ripe fruit rot caused by Monilinia or Botrytis results in firm, circular spots that spread rapidly over fruit. Monilinia causes dark brown lesions on fruit that eventually turn black from the development of pseudosclerotia (fungal tissue), whereas Botrytis causes light tan to grayish lesions with gray spores. Spore masses may grow on the rotted areas. Fruit becomes more susceptible as it ripens. Botrytis-diseased fruit usually do not remain on the tree until next season, but they are present as inoculum sources for the current season's crop. When Monilinia-diseased fruit remain on the tree, they are known as mummies.

Rhizopus rot is a postharvest storage problem. The decaying fruit tissue is watery and soft; the fungus is identified by masses of white mycelium with tiny black sporangia that form most abundantly on fruit near the edge of containers.

COMMENTS ON THE DISEASE

Monilinia and Botrytis can infect uninjured ripening fruit and cause green fruit rot and incipient infections of young fruit. Wetness, either rain or dew, and injury or fruit cracking increases preharvest infection and subsequent rot. Rhizopus spp. invades only ripe fruit that have been injured and the decay is a postharvest concern only.

MANAGEMENT

Fruit rot is managed by controlling blossom and twig blight in spring, removing blighted twigs when possible, using appropriate levels of nitrogen fertilizer and water, removing or turning under thinned fruit, controlling fruit-feeding insects such as peach twig borer and oriental fruit moth, and making preharvest treatments when necessary. Early maturing cultivars typically have little trouble with ripe fruit rot.

Take fruit samples every other week after color break (see PREHARVEST FRUIT SAMPLES) to detect any developing problems in the orchard and a fruit damage sample at harvest to assess the effectiveness of the current year's IPM program and to determine the needs of next year's program, see FRUIT EVALUATION AT HARVEST. Record results (115 KB, PDF) for harvest sample.

Organically Acceptable Methods
Treatments of sulfur dust are acceptable for use in an organically certified crop.

Chemical Control
Fungicides are preventive, not eradicative; they must be applied to uninjured fruit before infections occur. Injured fruit cannot be protected from Monilinia or Botrytis rot by preharvest sprays. 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. After harvest, Rhizopus can be controlled by storing the crop at temperatures below 40°F.

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 impact. Not all registered pesticides are listed. Always read label of product being used.
 
A. TEBUCONAZOLE/TRIFLOXYSTROBIN
  (Adament 50 WG) 4–8 oz/acre 5 days 1
  MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3) and Quinone outside inhibitor (11)
 
B. PROPICONAZOLE
  (Bumper, Tilt) 4 oz/acre Tilt: 12
Bumper: 24
0
  MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
  COMMENTS: Maximum of 2 preharvest sprays.
 
C. TEBUCONAZOLE
  (Elite, etc. 45WP) 4–8 oz/acre 12 0
  MODE OF ACTIONo GROUP NAME (NUMBER1): Demethylation inhibitor (3)
  COMMENTS: Do not apply more than 3 lb/acre/season.
 
D. FENBUCONAZOLE
  (Indar 75WSP) 2 oz/acre 12 0
  MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
  COMMENTS: Do not apply more than 1 lb/acre/season.
 
E. THIOPHANATE METHYL
  (Topsin-M, etc. 70W) 8 oz/100 gal water 12 1
  MODE OF ACTION GROUP NAME (NUMBER1): Methyl benzimidazole (1)
  COMMENTS: One application only per season and always apply with a companion fungicide with a different mode of action group number. Strains of brown rot resistant to thiophanate methyl have been found in California. If resistance has occurred in your orchard, do not use this fungicide.
   
F. PYRACLOSTROBIN/BOSCALID
  (Pristine) 10.5–14.5 oz/acre 12 0
  MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) and Carboxamide (7)
   
G. FENHEXAMID
  (Elevate 50 WDG) 1–1.5 lb/acre 12 0
  MODE OF ACTION GROUP NAME (NUMBER1): Hydroxyanilide (17)
  COMMENTS: Avoid making more than 2 consecutive applications of this material.
   
H. MYCLOBUTANIL
  (Rally 40W) 2.5–6 oz/acre 24 0
  MODE OF ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
   
I. CAPTAN 50WP 2 lb/100 gal water 24 0
  MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M4)
  COMMENTS: Do not apply in combination with, immediately before, or closely following oil sprays.
   
J. SULFUR DUST# 50 lb/acre see label see label
  MODE OF ACTION GROUP NAME (NUMBER1): Multi-site contact (M2)
  COMMENTS: Do not apply within 3 weeks of an oil application.
   
POSTHARVEST
A. FLUDIOXONIL
  (Scholar 50WP) 8–16 oz/100 gal water NA NA
  MODE OF ACTION GROUP NAME (NUMBER1): Phenylpyrrole (12)
  COMMENTS: Treats 200,000 lb fruit using a spray-application system.
 
+ 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.
# Acceptable for use on organically grown produce.
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 a fungicide with a different mode of action Group number.
NA Not applicable.

IMPORTANT LINKS

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Nectarine
UC ANR Publication 3451
Diseases
J. E. Adaskaveg, Plant Pathology, UC Riverside
R. A. Duncan, UC Cooperative Extension Stanislaus County
K. R. Day, UC Cooperative Extension, Tulare County
Acknowledgment for contributions to Diseases:
B. L. Teviotdale, Kearney Agricultural Center, Parlier
W. D. Gubler, Plant Pathology, UC Davis

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