Grey mold has a distinctive appearance that can potentially be identified with a microscope or even a good hand lens. It can grow on dead and decaying tissue and may cause various symptoms, including leaf and flower blights, spots, blotches, wilts, cankers, rots, damping off, and storage diseases.
[email protected] | Close up of grey mold (Botrytis)
Usually, softer tissues such as petals are blighted, though leaf spots, stem blights, and rotting of cuttings and seeds occur, especially in crowded situations. Tissue infected with grey mold tends to have masses of grey fungal growth, including spores.
Spores are spread by wind, water splash, insects such as bees and aphids, and handling of infected material. Spores can also be carried on seeds, cuttings, seedlings, and bulbs. The spores need moisture for germination and infection.
They are favored by cool, wet weather conditions when temperatures are below 25 Celsius (optimum temperatures are 18 – 23 C). Closed growing areas where humidity is high suit Botrytis infections. Autumn and spring overcast days and shorter day lengths are also favored. Grey mold can infect a very wide range of plant species. Some species (such as lisianthus and cyclamen) are extremely susceptible. Other hosts include viola, strawberry, pelargonium, blueberry, daisies, Corymbia spp., lavender, impatiens, rose, Cordyline, poinsettia, Dianella, Dietes, and many others.
If you suspect you are experiencing disease caused by this fungus, consider sending a sample for diagnostic testing. Initial results are often very fast owing to their distinctive spores that almost always occur on infected tissue. All production nurseries receive six free samples through Grow Help Australia, funded by Hort Innovation, the nursery levy, and the Queensland Department of Agriculture and Fisheries.
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