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Thrips attacking California roses (but not ours)

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

Sacramento Digs Gardening
BY Debbie Arrington PUBLISHED NOV 23, 2020

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.

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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Keywords:

entomology Sacramento American Rose Society pests roses thrips gardening fall weather Baldo Villegas invasive pest California rose care

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Dig In: Garden Checklist

For week of June 4:

Because of the comfortable weather, it’s not too late to set out tomato and pepper seedlings as well as squash and melon plants. They’ll appreciate this not-too-hot weather. Just remember to water.

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

* Plant basil to go with your tomatoes.

* Transplant summer annuals such as petunias, marigolds and zinnias.

* It’s also a good time to transplant perennial flowers including astilbe, columbine, coneflowers, coreopsis, dahlias, rudbeckia, salvia and verbena.

* 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 wee 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.

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

* Cut back fruit-bearing canes on berries.

* Feed camellias, azaleas and other acid-loving plants.

* 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.

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