Northwest berry Foundation

Management Detail

Botrytis Grey Mold (includes blossom blight and/or fruit rot)

in Strawberries

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Latin name: Botrytis cinerea

Description:

Reason for Concern:
1) Under the right environmental and field conditions (wet weather during fruit development and poor circulation in the canopy) it can cause significant yield losses.
2) Can remain dormant and disease symptoms do not show up until after the fruit has been harvested.
3) Losses are most severe in wet weather throughout harvest.

Identification/Symptoms:
Botrytis infects both blooms (called blossom blight) and fruit (called fruit rot). Blossom blight is characterized by petals and pedicels turning brown. The entire blossom may die. Fruit rot may occur on any portion of the fruit. It frequently develops at the calyx end and in tissues contiguous with rotting fruit or diseased flowers. Affected tissue turns light to medium brown. Lesions in green or white fruit develop slowly. The fruit may be misshapen as it enlarges. Fruit rot expands rapidly near harvest. In advanced stages, the fungus produces a gray mold over the fruit surface. Fruit can appear healthy at harvest but develop rot soon after.

Life Cycle:
Botrytis is a common fungus that cannot be eliminated from fields, only reduced. Same causal agent as blossom blight and fruit rot; the fungus overwinters on weeds and plant debris as black fungal bodies. In spring, under humid conditions, the spores infect new and mature growth via water or wind or direct contact with already infected plant parts.

Links:

Scouting:

  • Inspect petals and pedicels for the brown discoloration of blossom blight, particularly around periods of wet weather.
  • Fruit rot symptoms may occur on any portion of the fruit. Inspect calyx end of developing fruit as well as tissues contiguous with rotting fruit or diseased flowers for brown, soft lesions on fruit surface.
  • In advanced stages, the fungus produces a gray mold over the fruit surface.
  • Timing of preventative fungicide applications during bloom is essential to control of this disease.

 
Cultural Controls:

  • Microclimates and environmental factors greatly influence the incidence of Gray Mold. Staying on top of the harvest schedule and not allowing overripe fruit from accumulating in the field is essential for minimizing the disease incidence.
  • Renovating fields shortly after harvest is complete is important to decrease inoculum levels that overwinter on remaining fruit left in the field.
  • Plastic mulches or any other way to keep fruit from touching the soil helps reduce the disease inoculum.
  • Manage nitrogen fertilizer application appropriately to minimize soft fruit which is susceptible to Gray Mold.
  • Allow good air circulation for optimum drying by spacing plats appropriately and keeping weeds under control.

 

For information about chemical controls, check with our Pesticide Guide.

images


photo by T. Peerbolt


Blossom blight - photo by T. Peerbolt

 


Botrytis blight (also called fruit rot and grey mold) - photo by T. Peerbolt


Botrytis blight (also called fruit rot and grey mold) - photo by T. Peerbolt

 

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