Regardless of the plant part infected by Botrytis
, the affected tissue appears wet and turns tan to brown in color. Young fuzzy growth appears white to whitish-gray and eventually turns entirely gray. The fungus is very fast growing and capable of producing thousands of spores in grape like clusters that develop on rotting tissue. These spores are mostly spread by wind and water, but nearly any activity can spread Botrytis
spores in a greenhouse.
Daisies maintained in cold storage showing early stages of Botrytis blight on flower petals.
is often considered a cool weather pathogen and disease development is most often favored by cool and damp conditions with temperatures in the 70s and relative humidity at 90% or greater. Free moisture or high relative humidity is necessary for spore germination, so allowing the foliage to dry will help minimize disease. The fungus can be active at very low temperatures and can cause substantial loss of plant products in cold storage ranging from 32° to 50°F. Most cold storage units are maintained with high relative humidity to prevent shrinking or shriveling of plant material, so it’s very important to maintain strict sanitary measures and use fungicides preventatively when conditions are favorable.
requires direct contact with open wounds or an available food source such as diseased flower petals or pieces of debris that come into contact with healthy plant tissues for the infection process to begin. The Botrytis
-infected tissue serves as a potential source of inoculum, providing a substrate that the mycelium grows from and then penetrates underlying healthy plant tissue. This illustrates the importance of strict sanitation practices that includes removing and discarding dead blooms, leaves and all plant debris found on or under greenhouse benches and in plant beds.
When it comes to effective management of prolific pathogens such as Botrytis
, preventive fungicide applications are a must. It is critical that individuals making fungicide application decisions follow the manufacturer’s recommendation for proper rates and application intervals. Several fungicides have been developed for use on ornamentals plants for controlling Botrytis
(refer to table). The proper use of fungicides and recognizing the importance of rotating the Fungicide Resistance Action Committee (FRAC) groups for control of economically important plant diseases such as Botrytis blight will ensure long term success and future availability of fungicides for disease management.