This fungus is the major fungal problem in our gardening world. It is the grey mouldy stuff that appears on spent blossoms and attacks wounded leaves.
Think of it as Mother Nature’s shock troops – when there’s something that’s ready for composting, botrytis is sent in to start the job. When it’s done, other organisms take over.
This gives us the first clue about how it gets started.
Plants are under stress. This is normally being too crowded on the growing tables or garden.
High humidity is beloved of fungus everywhere and it’s no exception here.
Darkish conditions – either from shading or too much cloud cover outdoors is also a huge benefit to botrytis.
So what you’re looking at here is cleanliness is next to godliness. (at least that’s what my mom used to tell me when she looked into my bedroom while shaking her head) – leaving any kind of infected material around is a sure way to get other plants infected.
Space out your seedlings, keep them at the right temperatures, and make sure there’s adequate ventilation around the seedlings to keep those leaves dry.
Do those things right and your need for a spray will be eliminated.
Look closely at the stems and flowers in this pic and you’ll see the start of the fungal infections.