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Weird weather brings botrytis outbreak


This poor Pink Promise hybrid tea rose was turned into a brown mess by botrytis. (Photo: Debbie Arrington)

Fungal disease loves cool, cloudy, moist conditions




“What is this and how can I fix it?”

That question came attached to a photo of what should have been a big beautiful red rose. Instead, each petal was deeply edged in brown.

In the days ahead, more Sacramento roses will seem to stop opening in mid-bloom and suddenly become covered with spots and brown patches. If left on the bush, these flowers turn to yucky gray mush.

It’s an early outbreak of botrytis, a common fungus that attacks a broad range of ornamental and edible plants.

Usually, local gardeners don’t see Botrytis cinerea on their roses until October or November. But recent weather conditions have been just right for this opportunistic pathogen. Botrytis loves temperatures in the 70s, cloudy afternoons and a little rain.

It’s that splash of moisture that really launched this attack – both in April and now in May. Botrytis needs moisture for growth in plant tissues and what it loves are tender flower petals. It can’t seem to resist a wet bud on a cool, cloudy day.

Nicknamed gray mold, botrytis will eventually overwhelm the flower and turn it into soft mush. The earliest stages look like pink measles or brownish water spots on light colored flowers. Those brown spots quickly grow until they consume the whole petal. The fungus grows so fast, the flower never fully opens.

Although botrytis is common in the fall, a spring attack seems worse because we have more flowers in the garden.

Besides roses, botrytis 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 botrytis 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.

When the heat returns (which will be soon), botrytis will disappear – it can’t stand temperatures over 90 degrees. But expect it to come back again in October – especially after the first fall rain.

For more information on botrytis, check out these pest notes from UC IPM:
http://ipm.ucanr.edu/PMG/r280100511.html

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Garden checklist for week of May 24

Take advantage of this “normal” week and get stuff done. Your garden needs you.

* Plant, plant, plant! It’s prime planting season in the Sacramento area. Time to set out those tomato transplants along with peppers and eggplants. Pinch off any flowers on new transplants to make them concentrate on establishing roots instead of setting premature fruit.

* Support with trellises, cages or stakes rapidly growing tomatoes, peppers, eggplants or other tall crops that may get knocked around in those gusty winds.

* Direct-seed melons, cucumbers, summer squash, corn, radishes, pumpkins and annual herbs such as basil.

* Harvest cabbage, lettuce, peas and green onions.

* In the flower garden, direct-seed sunflowers, cosmos, salvia, zinnias, marigolds, celosia and asters. (You also can transplant seedlings for many of the same flowers.)

* Plant dahlia tubers. 

* Transplant petunias, marigolds and perennial flowers such as astilbe, columbine, coneflowers, coreopsis, dahlias, rudbeckia and verbena.

* Remember to irrigate your tender transplants. Seedlings need consistent moisture. Deep watering will help build strong roots and healthy plants. Water early in the morning for best results.

* Keep an eye out for slugs, snails, earwigs and aphids that want to dine on tender new growth.

* Feed summer bloomers with a balanced fertilizer.

* For continued bloom, cut off spent flowers on roses as well as other flowering plants.

* Put your veggie garden on a regular diet. Set up a monthly feeding program, and keep track on your calendar. Make sure to water your garden before applying any fertilizer to prevent “burning” your plants.

* As spring-flowering shrubs finish blooming, give them a little pruning to shape them, removing old and dead wood. Lightly trim azaleas, fuchsias and marguerites for bushier plants.

* Don’t forget to weed! Those invaders are growing fast.

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Food in My Back Yard (FIMBY) Series

Lessons learned during a year of edible gardening

WINTER

Is edible gardening possible indoors?

Hints for choosing tomato seeds

Starting in seed starting

Why winter is the perfect time to plant fruit trees

When to plant? Consider staggering your transplants

How to squeeze more food into less space

Potatoes from the garden

Plant a fruit tree now -- for later

Win the weed war by tackling them in winter

Tips for planting bare-root trees, shrubs and vegetables

Time to give vegetable seedlings some more space

Ways to win the fight against weeds

FALL

Dec. 16: Add asparagus to your edible garden

Dec. 9: Soggy soil and what to do about it

Dec. 2: Plant artichokes now; enjoy for years to come

Nov. 25: It's late November, and your peach tree needs spraying

Nov. 18: What to do with all those fallen leaves?

Nov. 11: Prepare now for colder weather in the edible garden

Nov. 4: Plant a pea patch for you and your garden

Oct. 27: As citrus season begins, advice for backyard growers

Oct. 20: Change is in the autumn air 

Oct. 13: We don't talk (enough) about beets

Oct. 6: Fava beans do double duty

Sept. 30: Seeds or transplants for cool-season veggies?

Sept. 23: How to prolong the fall tomato harvest 

SUMMER

Sept. 16: Time to shut it down? 

Sept. 9: How to get the most out of your pumpkin patch

Sept. 2: Summer-to-fall transition time for evaluation, planning

Aug. 26: To pick or not to pick those tomatoes?

Aug. 19: Put worms to work for you

Aug. 12: Grow food while saving water

Aug. 5: Enhance your food with edible flowers

July 29: Why won't my tomatoes turn red?

July 22: A squash plant has mosaic virus, and it's not pretty

July 15: Does this plant need water?

July 8: Tear out that sad plant or baby it? Midsummer decisions

July 1: How to grow summer salad greens

June 24:  Weird stuff that's perfectly normal

SPRING

June 17: Help pollinators help your garden

June 10: Battling early-season tomato pests

June 3: Make your own compost

May 27: Where are the bees when you need them?

May 20: How to help tomatoes thrive on hot days

May 13: Your plants can tell you more than any calendar can

May 6: Maintain soil moisture with mulch for garden success

April 29: What's (already) wrong with my tomato plants?

April 22: Should you stock up on fertilizer? (Yes!)

April 15: Grow culinary herbs in containers

April 8: When to plant summer vegetables

April 1: Don't be fooled by these garden myths

March 25: Fertilizer tips: How to 'feed' your vegetables for healthy growth