UC IPM Online UC ANR home page UC IPM home page

UC IPM Home

Search

SKIP navigation

Home & garden
Agriculture
Natural environments
Exotic & invasive

Weather data & products
Degree-days
Interactive tools & models

Publications & more
Workshops and events
Training programs
Pesticide information

Grants programs
Funded-project results


 

How to Manage Pests

UC Pest Management Guidelines


Botrytis fruit rot spores covering blackberry fruit.

Caneberries

Botrytis Fruit Rot

Pathogen: Botrytis cinerea

(Reviewed 5/08, updated 5/08)

In this Guideline:


SYMPTOMS

Flattened black masses of sclerotia appear on the bleached appearing canes of Botrytis-infested blackberry and raspberry plants in late winter. In the presence of free water during spring, sclerotia germinate to form masses of gray mycelium and spores called conidia. Opened flowers may become infected, and the fungus will sporulate on the blighted flowers. On infected druplets, a watery rot may precede the development of grayish brown conidia and hyphae. The conidia and hyphae eventually cover the fruit. Infected berries left on the vines become mummified. If the weather is moist after harvest, the receptacles can be colonized by the fungus and sclerotia can develop. In postharvest storage, white mycelia can cover infected berries.

COMMENTS ON THE DISEASE

Botrytis fruit rot occurs under cool, wet conditions. (The pathogen requires free water for sclerotial germination, spore germination, and infection.) Physical damage to the fruit increases disease incidence, especially during the rainy season. The pathogen overwinters as sclerotia on infected canes and as mycelium in infected leaves and canes on the ground. The main sources of primary inoculum are conidia from overwintering sclerotia and dead leaves, and conidia from mummified berries. Conidia are dispersed by wind, rain, and overhead irrigation. Flowers are not susceptible to infection until they are open. Infections generally remain dormant until fruit is nearly ripe or after harvest. Infections can recur throughout the season by sporulation of the fungus on unpicked, leaky, overripe fruit left on the vine.

MANAGEMENT

To promote air circulation and quicken drying of plant tissue, prune and trellis the plants to open the canopy. A narrow row can be maintained by removing the first flush of primocanes (first-year canes), minimizing nitrogen fertilizer application, and controlling weeds. Training systems also help to maintain an open canopy. Partial resistance to this disease is available for red raspberry cultivars. To prevent postharvest fruit rot, pick fruit when it is in the red ripe stage of development (before reaching full maturity). Avoid fruit injury and remove receptacles from berries after picking because these fleshy structures can become a major source of inoculum in the harvested fruit. Pack fruit directly into containers, and use shallow containers to avoid crushing. Pick fruit often, and pick early in the day when temperatures are cool; cool fruit to 34° to 36°F as soon as possible after harvest. Store fruit at about 36°F to maintain firmness and to prevent condensation inside the closed basket or clamshell. Fungicides are applied as protectant sprays at 7- to 14-day intervals from early bloom up to harvest.

Organically Acceptable Methods
Pruning and/or using a training system to open the canopy, proper fertilization, weed control, resistant cultivars, and proper harvest techniques are all acceptable for use in an organically certified crop.

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

When choosing a pesticide, consider the general properties of the fungicide as well as information relating to environmental impact.
 
A. IPRODIONE
  (Rovral) 4 F 1–2 pt 24 0
  MODE OF ACTION GROUP NAME (NUMBER1): Dicarboximide (2)
  COMMENTS: Apply in a minimum of 100 gal water/acre. Do not make more than 4 applications/crop/season.
 
B. FENHEXAMID
  (Elevate) 50 WDG 1.5 lb 12 0
  MODE OF ACTION GROUP NAME (NUMBER1): Hydroxyanilide (17)
  COMMENTS: Begin application at 10% bloom and reapply every 7 days or when conditions favor disease development. Do not apply more than 6 lb/acre/season. Avoid making two consecutive applications.
 
C. PYRACLOSTROBIN/BOSCALID
  (Pristine) 18.5–23 oz 12 0
  MODE OF ACTION GROUP NAME (NUMBER1): Quinone outside inhibitor (11) and Carboxamide (7)
  COMMENTS: Restricted entry interval is 12 hours. To limit the potential for development of resistance, do not apply more than 4 application of this or other Group 7 and 11 fungicides per season.
 
D. CYPRODINIL/FLUDIOXONIL
  (Switch) 62.5 WG 11–14 oz 12 0
  MODE OF ACTION GROUP NAME (NUMBER1): Anilinopyrimidine (9) and Phenylpyrrole (12)
  COMMENTS: Make no more than two sequential applications before switching to a fungicide with a different Group number mode of action. Do not apply more than 56 oz/acre/year.
 
+ 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.

[Precautions]

PUBLICATION

[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Caneberries
UC ANR Publication 3437
Diseases
S. T. Koike, UC Cooperative Extension, Monterey County
M. P. Bolda, UC Cooperative Extension, Santa Cruz County
E. J. Perry, UC Cooperative Extension, Stanislaus County
W. D. Gubler, Plant Pathology, UC Davis
L. J. Bettiga, UC Cooperative Extension, Monterey County

Top of page


Statewide IPM Program, Agriculture and Natural Resources, University of California
All contents copyright © 2008 The Regents of the University of California. All rights reserved.

For noncommercial purposes only, any Web site may link directly to this page. FOR ALL OTHER USES or more information, read Legal Notices. Unfortunately, we cannot provide individual solutions to specific pest problems. See How to manage pests, or in the U.S., contact your local Cooperative Extension office for assistance. /PMG/r71100211.html revised: May 30, 2008. Contact webmaster.