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Weird weather brings botrytis outbreak

Sacramento Digs Gardening
BY Debbie Arrington PUBLISHED MAY 12, 2020

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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GENERAL GARDENING

An article about gardening.

Keywords:

gardening Sacramento integrated pest management roses botrytis pathogens disease control UC IPM plant diseases

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Food in My Back Yard (FIMBY) Series

FALL

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

WINTER

March 18: Time to give vegetable seedlings some more space

March 11: Ways to win the fight against weeds

March 4: Potatoes from the garden

Feb. 25: Plant a fruit tree now -- for later

Feb. 18: How to squeeze more food into less space

Feb. 11: When to plant? Consider staggering your transplants

Feb. 4: Starting in seed starting

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Garden checklist for week of Nov. 16

During breaks in the weather, tackle some garden tasks:

* Clear gutters and storm drains.

* Prune dead or broken branches from trees.

* After the storm, seed wildflowers and plant such spring bloomers as sweet pea, sweet alyssum and bachelor buttons.

* Set out cool-weather annuals such as pansies and snapdragons.

* Lettuce, cabbage and broccoli also can be planted now.

* Plant garlic and onions.

* Plant bulbs at two-week intervals to spread out your spring bloom. Some possible suggestions: daffodils, crocuses, hyacinths, tulips, anemones and scillas.

* Save dry stalks and seedpods from poppies and coneflowers for fall bouquets and holiday decorating.

* 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 them. Do leave some (healthy) leaves in the planting beds for wildlife and beneficial insect habitat.

* Give your azaleas, gardenias and camellias a boost with chelated iron.

* For larger blooms, pinch off some camellia buds.

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