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 April 21
This week there’s plenty to keep gardeners busy. With no rain in the immediate forecast, remember to irrigate any new transplants.
* Weed, weed, weed! Get them before they flower and go to seed.
* April is the last chance to plant citrus trees such as dwarf orange, lemon and kumquat. These trees also look good in landscaping and provide fresh fruit in winter.
* Smell orange blossoms? Feed citrus trees with a low dose of balanced fertilizer (such as 10-10-10) during bloom to help set fruit. Keep an eye out for ants.
* Apply slow-release fertilizer to the lawn.
* Thoroughly clean debris from the bottom of outdoor ponds or fountains.
* Spring brings a flush of rapid growth, and that means your garden is really hungry. Feed shrubs and trees with a slow-release fertilizer. Or mulch with a 1-inch layer of compost.
* Azaleas and camellias looking a little yellow? If leaves are turning yellow between the veins, give them a boost with chelated iron.
* Trim dead flowers but not leaves from spring-flowering bulbs such as daffodils and tulips. Those leaves gather energy to create next year's flowers. Also, give the bulbs a fertilizer boost after bloom.
* Pinch chrysanthemums back to 12 inches for fall flowers. Cut old stems to the ground.
* Mulch around plants to conserve moisture and control weeds.
* From seed, plant beans, beets, cantaloupes, carrots, corn, cucumbers, melons, radishes and squash.
* Plant onion sets.
* In the flower garden, plant seeds for asters, cosmos, celosia, marigolds, salvia, sunflowers and zinnias.
* Transplant petunias, zinnias, geraniums and other summer bloomers.
* Plant perennials and dahlia tubers for summer bloom.
* Mid to late April is about the last chance to plant summer bulbs, such as gladiolus and tuberous begonias.
* Transplant lettuce seedlings. Choose varieties that mature quickly such as loose leaf.
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