Bye Bye Botrytis
Last week, in preparation for what appears to be a long, warm, winter, I planted four flats of pansies, two flats of snapdragons and some camellias. Now, I have to see if botrytis strikes. I certainly hope it doesn’t, as I prefer to not spray my plants with anything, if possible, even organic fungicides. However, if it does strike, I suppose I will treat it. After all, from planting I have a huge blister on my left hand that probably won’t go away for a couple of weeks, and I wouldn’t want to lose those plants.
What is Botrytis?
Botrytis is a genera of fungus. It attacks ornamental plants and food plants, causing brown spots and a grey mold. In cooler climates, the fungus attacks during the spring and fall when humidity is high and the temperatures are warm. In warmer climates, the fungus is more prevalent when the winters are warm and humid. If your plants begin deveoping squishy brown spots (not dry brown spots) on the flowers or leaves, you might have a botrytis outbreak. As a fungus, botrytis spreads by spores. The mycelia (which look kind of like spreading roots, but are actually just another part of the fungus) survive cooler periods and re-sprout when the weather warms.
How do you control Botrytis?
The best Botrytis control mechanism is cultural control. You can pick off any infected leaves or flowers, and throw them away. (You should never compost diseased plant material, as you run the risk of spreading the disease to every single other plant around which you spread the compost.) If an entire plant is badly infected, you should dig up the plant and throw away the entire plant. Because the spores spread rapidly through water, never work on cultural control mechanisms when the plants are wet. Additionally, if you use any tools to remove botrytis infected plant material, you will want to thoroughly disinfect your tools before using them on other plants. To keep fungal spores from overwintering in large quantities, always rake up and remove any dead plant material from your garden, when possible. For fewer problems in the next season, you can also rotate the plants that are affected by botrytis to different areas of the garden, to avoid planting them where the fungus has been in the past. The effectiveness of cultural control cannot be overstated, when it comes to botrytis.
Because of widespread use, synthetic fungicides are becoming less and less effective against botrytis infections. Biological control agents are still in early stages of testing for effectiveness, but you can purchase and test biological fungicides that are organic to treat your botrytis inflicted plants. There are several brand names, but most of these organic fungicides have Trichoderma and Cladosporium as the biological control agents in the compound. You can try sulfur-based organic fungicides if the biological fungicides do not work. Patience and persistance is key.
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