DISEASES

Botrytis Blight
(Botrytis cinerea)

Most susceptible plants: exacum, geranium, impatiens.

Probably the most common and troubling greenhouse pathogen is the gray mold fungus, Botrytis cinerea. Botrytis can infect any above-ground portion of the plant. Wounded or stressed tissues are much more susceptible to infection. Botrytis can cause serious problems in geranium both as a flower blight as well as a stem/cutting rot.

Symptoms:
Diagnosis is usually straightforward and is characterized by the obvious gray-to-brown fuzzy growth on infected plant tissue. This disease is much more common when relative humidity is high, when air stagnation is present, when temperatures are cool and where free moisture occurs on plant parts.

Control:

  • Avoid injury or stress to plants.
  • Encourage good air circulation and air movement within the greenhouse.
  • Space plants so as to encourage air movement around individual plants.
  • Use night heat plus ventilation at night to lower relative humidity within the greenhouse.
  • Keep temperatures above 60ÉC if possible.
  • Thorough greenhouse sanitation is MANDATORY! Remove infected plant material and plant debris.
  • Fungicide application may be effective if started early and if fungicides are rotated.