The most common species of blight is caused by Botrytis cinerea. Botrytis infections are favoured by cool, rainy spring and summer weather usually around 15°C. Commonly called, Gray mould, Botrytis can be particularly damaging when rainy, drizzly weather continues over several days.
Botrytis blight can affect leaves, stems, crowns, flowers, flower buds, seeds, seedlings, bulbs, and just about any other part of a plant with the exception of the roots, and it therefore affects a wide range of ornamental flowers, fruits and vegetables. Fortunately, this fungus usually prefers certain plant parts on each kind of plant it attacks. On most susceptible plants, new infections may begin in the spring as soon as weather conditions are favourable for disease development. Wet or very humid weather may be highly favourable for the spread of the disease. For some Botrytis spp., sclerotia develop in dead plant tissue and form the overwintering stage of the fungus. Fungal mycelium may also overwinter in woody stem debris. Sclerotia then germinate in the spring, or mycelium grows out of infected debris and conidia (infectious spores) develop. Conidia may be windborne or rain-splashed to cause new infections on susceptible host tissue.
realIPM recommends a holistic approach to managing Botrytis from the soil up by ensuring the plants have adequate and appropriate nutrients and drainage, as well as protection in the form of Real Bacillus or Copper Soap. However, each farm is unique and the best results are achieved when we consult with our clients on their farm.
Image adapted from: Plant Pathology 4th Edition by George Agrios
Botrytis Blight: Botrytis cinerea; Botrytis spp. Plant Disease Diagnostic Clinic Plant Pathology and Plant‐Microbe Biology Section. College of Agriculture and Life Sciences. Cornell University.