Foggy conditions prompted recent outbreak
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| 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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Garden Checklist for week of Nov. 3
November still offers good weather for fall planting:
* If you haven't already, it's time to clean up the remains of summer. Pull faded annuals and vegetables. Prune dead or broken branches from trees.
* Now is the best time to plant most trees and shrubs. This gives them plenty of time for root development before spring growth. They also benefit from fall and winter rains.
* Set out cool-weather annuals such as pansies and snapdragons.
* Lettuce, cabbage and broccoli also can be planted now.
* Plant garlic and onions.
* Keep planting bulbs to spread out your spring bloom. Some possible suggestions: daffodils, crocuses, hyacinths, tulips, anemones and scillas.
* This is also a good time to seed wildflowers and plant such spring bloomers as sweet pea, sweet alyssum and bachelor buttons.
* Rake and compost leaves, but dispose of any diseased plant material. For example, if peach and nectarine trees showed signs of leaf curl this year, clean up under trees and dispose of those leaves instead of composting.
* Save dry stalks and seedpods from poppies and coneflowers for fall bouquets and holiday decorating.
* For holiday blooms indoors, plant paperwhite narcissus bulbs now. Fill a shallow bowl or dish with 2 inches of rocks or pebbles. Place bulbs in the dish with the root end nestled in the rocks. Add water until it just touches the bottom of the bulbs. Place the dish in a sunny window. Add water as needed.
* Give your azaleas, gardenias and camellias a boost with chelated iron.
* For larger blooms, pinch off some camellia buds.
* Prune non-flowering trees and shrubs while dormant.
* To help prevent leaf curl, apply a copper fungicide spray to peach and nectarine trees after they lose their leaves this month. Leaf curl, which shows up in the spring, is caused by a fungus that winters as spores on the limbs and around the tree in fallen leaves. Sprays are most effective now.
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