Agriculture: Peach Pest Management Guidelines

Ripe Fruit Rot

  • Ripe fruit rot: Botrytis cinerea, Monilinia fructicola, Rhizopus spp.
  • 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.

    Examine fruit on trees every other week after color break (see PREHARVEST FRUIT SAMPLES) to detect any developing problems in the orchard and take 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 for the harvest (PDF) 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 per acre REI‡ PHI‡
    (Example trade name) (hours) (days)
    Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide's properties and application timing, honey bees, and environmental impact. Always read the label of the product being used.
     
    A. TEBUCONAZOLE/TRIFLOXYSTROBIN
      (Adamant 50WG) 4–8 oz 5 days 1
      MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3) and Quinone outside inhibitor (11)
     
    B. PROPICONAZOLE
      (Bumper, Tilt) 4 fl oz 12 0
      MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
      COMMENTS: Maximum of 2 preharvest sprays.
     
    C. TEBUCONAZOLE
      (Elite 45WP) 4–8 oz 120 (5 days) 0
      MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
      COMMENTS: Do not apply more than 3 lb/acre per season.
     
    D. FENBUCONAZOLE
      (Indar 2F) 6 fl oz 12 0
      MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
      COMMENTS: Do not apply more than 1 lb/acre per season.
     
    E. THIOPHANATE METHYL
      (Topsin-M 70WP) 1 ½ lb 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. METCONAZOLE
      (Quash) 2.5–4 oz 12 14
      MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
      COMMENTS: Do not make more than 3 applications per season.
     
    G. PYRACLOSTROBIN/BOSCALID
      (Pristine) 10.5–14.5 oz 12 0
      MODE-OF-ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) and Carboxamide (7)
     
    H. 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 2 consecutive applications of this material.
     
    I. MYCLOBUTANIL
      (Rally 40WSP) 2.5–6 oz 24 0
      MODE-OF-ACTION GROUP NAME (NUMBER1): Demethylation inhibitor (3)
     
    J. CAPTAN
      (Captan 50WP) 4–8 lb 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.
     
    K. SULFUR DUST# 50 lb 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) 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 (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.
    # 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

    Text Updated: 09/15
    Treatment Table Updated: 09/15