Fungal disease prompted by wet weather; tips for stopping its spread
This Pink Promise rose is showing damage from botrytis, a fungus also called gray mold. Debbie Arrington
Here I was, with a garden full of December rose buds prompting visions of gift bouquets. Then came the rain – and most of those beautiful buds turned to mush.
It was an attack of gray mold, and another reminder that it’s time to prune.
Gray mold is the descriptive nickname of the fungal disease botrytis. It’s common in late fall and early winter rose gardens, and this season’s outbreak looks particularly yucky.
Recent rain storms 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 the 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 of them 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 and blooms. (This contains other fungal spores, too, for powdery mildew, rust, black spot and other rose diseases.) Dispose of that old mulch and replace it with fresh mulch.
For more information on gray mold, check out these pest notes from UC IPM: http://ipm.ucanr.edu/PMG/r280100511.html
Comments
0 comments have been posted.Sacramento Digs Gardening to your inbox.
Thanks to Our Sponsor!
Local News
Sites We Like
Garden Checklist for week of Jan. 12
Once the winds die down, it’s good winter gardening weather with plenty to do:
* Prune, prune, prune. Now is the time to cut back most deciduous trees and shrubs. The exceptions are spring-flowering shrubs such as lilacs.
* Now is the time to prune fruit trees. (The exceptions are apricot and cherry trees, which are susceptible to a fungus that causes dieback. Save them until summer.) Clean up leaves and debris around the trees to prevent the spread of disease.
* Prune roses, even if they’re still trying to bloom. Strip off any remaining leaves, so the bush will be able to put out new growth in early spring.
* Clean up leaves and debris around your newly pruned roses and shrubs. Put down fresh mulch or bark to keep roots cozy.
* After the wind stops, apply horticultural oil to fruit trees to control scale, mites and aphids. Oils need 24 hours of dry weather after application to be effective.
* This is also the time to spray a copper-based fungicide to peach and nectarine trees to fight leaf curl. (The safest effective fungicides available for backyard trees are copper soap -- aka copper octanoate -- or copper ammonium, a fixed copper fungicide. Apply either of these copper products with 1% horticultural oil to increase effectiveness.)
* When forced bulbs sprout, move them to a cool, bright window. Give them a quarter turn each day so the stems will grow straight.
* Browse through seed catalogs and start making plans for spring and summer.
* Divide daylilies, Shasta daisies and other perennials.
* Cut back and divide chrysanthemums.
* Plant bare-root roses, trees and shrubs.
* Transplant pansies, violas, calendulas, English daisies, snapdragons and fairy primroses.
* In the vegetable garden, plant fava beans, head lettuce, mustard, onion sets, radicchio and radishes.
* Plant bare-root asparagus and root divisions of rhubarb.
* In the bulb department, plant callas, anemones, ranunculus and gladioli for bloom from late spring into summer.
* Plant blooming azaleas, camellias and rhododendrons. If you’re shopping for these beautiful landscape plants, you can now find them in full flower at local nurseries.
Powered by California Local
