Foggy conditions prompted recent outbreak
|Gray mold, also called botrytis, ruins rose blooms. (Photo: Debbie Arrington)|
Gray mold has me feeling blue. I love autumn roses. Hundreds of rosebuds in my garden had me envisioning fresh bouquets this holiday season.
But most of these November roses will never open. Instead, they turn to mush on the stem.
The reason? Gray mold. That’s the descriptive nickname of the fungal disease botrytis. It’s common in November rose gardens, and this season’s outbreak looks particularly yucky.
Rain storms in early November kicked it into full gear. Recent foggy conditions nurtured its rapid advancement.
Gray mold – which actually looks more tan or brown on the rosebud – needs moisture for growth in plant tissues, particularly tender flower petals. To prevent outbreaks, keep flower buds dry. That’s all but impossible on damp, foggy days.
Gray mold starts out looking like pink measles or brownish water spots on light-colored flowers. Those brown spots rapidly grow until the fungus consumes the whole petal. The flower never fully opens.
Gray mold also attacks African violet, asters, begonia, carnation, chrysanthemum, cyclamen, cymbidium, gerbera, geranium, gladiolus, hydrangea, marigolds, orchids, petunia, poinsettia, primrose, ranunculus, snapdragon, zinnia and many other garden favorites.
According to UC Integrated Pest Management program, the best control of gray mold is “good sanitation.” Clip off infected blooms, put them in a plastic bag and dispose in the trash. Do not compost them; that just recycles the spores back into the garden.
Pick up fallen blooms and petals around the bush and dispose of them, too. After pruning when roses are dormant, rake out old mulch and fallen foliage. (This contains other fungal spores, too, for powdery mildew, rust, black spot and other rose diseases.) Then dispose of that old mulch and replace with fresh mulch.
For more information on gray mold, check out these pest notes from UC IPM: http://ipm.ucanr.edu/PMG/r280100511.html
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For week of Dec. 10:
Take advantage of these dry but crisp conditions. It’s time to get out the rake!
* Rake leaves away from storm drains and keep gutters clear.
* Fallen leaves can be used for mulch and compost. Chop up large leaves with a couple of passes with a lawn mower.
* Prune non-flowering trees and shrubs while they’re dormant. Without their foliage, trees are easier to prune.
* Rake and remove dead leaves and stems from dormant perennials.
* Make sure to take frost precautions with new transplants and sensitive plants. Mulch, water and cover tender plants in the late afternoon to retain warmth.
* Succulent plants are at particular risk if temperatures drop below freezing. Don’t water succulents before frost; cover instead. Use cloth sheets, not plastic. Make sure to remove coverings during the day.
* Clean and sharpen garden tools before storing for the winter.
* Brighten the holidays with winter bloomers such as poinsettias, amaryllis, calendulas, Iceland poppies, pansies and primroses.
* Keep poinsettias in a sunny, warm location. Water thoroughly. After the holidays, feed your plants monthly so they'll bloom again next December.
* Just because it rained doesn't mean every plant got watered. Give a drink to plants that the rain didn't reach, such as under eaves or under evergreen trees. Also, well-watered plants hold up better to frost than thirsty plants.
* Plant garlic (December's the last chance -- the ground is getting cold!) and onions for harvest in summer.
* Bare-root season begins. Plant bare-root berries, kiwifruit, grapes, artichokes, horseradish and rhubarb. Beware of soggy soil. It can rot bare-root plants.
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