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Thrips attacking California roses (but not ours)

Chilli thrips vs. citrus thrips; what's the difference?

Damaged rose
This rose shows damage from chilli thrips.
(Courtesy of the San Diego Rose Society)
.



What’s in a name? When it comes to tiny thrips, the difference can be huge.

Right now, Southern California rose growers report a massive outbreak of chilli thrips. (Yes, that's with two lower-case L's.) As the name implies, these thrips prefer to dine on peppers, but they also find autumn roses irresistible.

Enjoying warm autumn weather, chilli thrips attack the buds and blooms, causing deformed flowers and ugly scarring. These thrips also can cause disfigured and distorted foliage and fruit.

The chilli thrip outbreak in Southern California was so severe, the American Rose Society put out an alert to rose growers and gardeners throughout the state.

But not here (yet). The thrips doing similar damage in the greater Sacramento area are a different species and (thankfully) not quite as voracious. Citrus thrips, another crossover pest, have been found in the greater Sacramento area. (But they shouldn’t be confused with yet another thrip, the much more common Western flower thrip.)

Originally native to India, chilli thrips have been a problem in several parts of the United States for years (Florida in particular), but only recently have started invading California.

“I was the one who discovered it,” said Sacramento’s Bug Man, Baldo Villegas. Now retired, the former state entomologist confirmed the chilli thrips as far north as Bakersfield and Wasco in 2016.

Chilli thrip
This is a chilli thrip, Scirtothrips dorsalis, which has not
yet been seen in Northern California. (Photograph
courtesy the University of Florida)

“Right now, they’re not here yet,” Villegas said. “We have citrus thrips, not chilli thrips. The damage looks very similar but not as bad.”

Citrus thrips, considered a threat to California’s citrus industry, attack fruit as it’s forming, causing scarring and deformities. In roses, citrus thrips also cause deformed buds and flowers. Fortunately, this thrip can’t stand cold and tends to disappear when temperatures stay below 58 degrees F.

Both thrips are tiny – under 2 millimeters long. Chilli thrip eggs are microscopic. This pest inserts its eggs into the buds of flowers.

If those blooms are destined to be cut flowers, those bouquets help move this pest around the world.

Which brings this reminder: Be careful where you get your flowers – and cuttings. To keep pests away, stay local.

Unfortunately for thrip control, rose hobbyists like to take and share cuttings in order to add new roses to their gardens. Villegas cited a rose conference at the Huntington Library’s famed rose garden, where several participants took cuttings and brought them home to Sacramento.

“I would discourage taking cuttings (of roses) in Southern California,” Villegas said. “If you do take a cutting from anywhere right now, I would disinfect it before bringing it home.”

Villegas suggested stripping off the leaves, dipping the cutting in soapy water and, just to be sure, spraying it with a systemic pesticide. That will kill invasive thrips – chilli, citrus or otherwise – and prevent introducing them to your own garden.

For more on thrips:

Chilli thrips:
http://entnemdept.ufl.edu/creatures/orn/thrips/chilli_thrips.htm

Citrus thrips: https://www2.ipm.ucanr.edu/agriculture/citrus/Citrus-Thrips/

Western flower thrips: https://www2.ipm.ucanr.edu/agriculture/lettuce/Western-flower-thrips/

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Garden checklist for week of June 14

We'll be back to normal temperatures for mid-June (about 86 degrees) by Thursday. In the meanwhile:

* Let the grass grow longer. Set the mower blades high to reduce stress on your lawn during summer heat. To cut down on evaporation, water your lawn deeply during the early hours of the morning, between 2 and 8 a.m.

* Tie up vines and stake tall plants such as gladiolus and lilies. That gives their heavy flowers some support.

* Dig and divide crowded bulbs after the tops have died down.

* Feed summer flowers with a slow-release fertilizer.

* Mulch, mulch, mulch! This “blanket” keeps moisture in the soil longer and helps your plants cope during hot weather.

* Avoid pot “hot feet.” Place a 1-inch-thick board under container plants sitting on pavement. This little cushion helps insulate them from radiated heat.

* Thin grapes on the vine for bigger, better clusters later this summer.

* Cut back fruit-bearing canes on berries.

* Warm weather brings rapid growth in the vegetable garden, with tomatoes and squash enjoying the heat. Deep-water, then feed with a balanced fertilizer. Bone meal can spur the bloom cycle and help set fruit.

* Generally, tomatoes need deep watering two to three times a week, but don't let them dry out completely. That can encourage blossom-end rot.

* Feed camellias, azaleas and other acid-loving plants. Mulch to conserve moisture and reduce heat stress.

* Cut back Shasta daisies after flowering to encourage a second bloom in the fall.

* Trim off dead flowers from rose bushes to keep them blooming through the summer. Roses also benefit from deep watering and feeding now. A top dressing of aged compost will keep them happy. It feeds as well as keeps roots moist.

* Pinch back chrysanthemums for bushier plants with many more flowers in September.

* From seed, plant corn, pumpkins, radishes, squash and sunflowers.

* Plant basil to go with your tomatoes. There’s still time to plant melons, pumpkins and squash from seed.

* Transplant summer annuals such as petunias, marigolds and zinnias. It’s also a good time to transplant perennial flowers including astilbe, bidens, columbine, coneflowers, coreopsis, dahlias, rudbeckia, salvia and verbena.

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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