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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:

Citrus thrips:

Western flower thrips:


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For week of Dec. 3:

Make the most of gaps between raindrops. This is a busy month!

* Windy conditions brought down a lot of leaves. Make sure to rake them away from storm drains.

* Use those leaves as mulch around frost-tender shrubs and new transplants.

* Rake and remove dead leaves and stems from dormant perennials.

* Just because it rained doesn't mean every plant got watered. Give a drink to plants that the rain didn't reach, such as under eves or under evergreen trees. Also, well-watered plants hold up better to frost than thirsty plants.

* Prune non-flowering trees and shrubs while they're dormant.

* Clean and sharpen garden tools before storing for the winter.

* Brighten the holidays with winter bloomers such as poinsettias, amaryllis, calendulas, Iceland poppies, pansies and primroses.

* Keep poinsettias in a sunny, warm location. Water thoroughly. After the holidays, feed your plants monthly so they'll bloom again next December.

* Plant one last round of spring bulbs including daffodils, crocuses, hyacinths, anemones and scillas. Get those tulips out of the refrigerator and into the ground.

* This is also a good time to seed wildflowers such as California poppies.

* Plant such spring bloomers as sweet pea, sweet alyssum and bachelor buttons.

* Late fall is the best time to plant most trees and shrubs. This gives them plenty of time for root development before spring growth. They also benefit from fall and winter rains.

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

* Plant garlic and onions.

* Bare-root season begins. Plant bare-root berries, kiwifruit, grapes, artichokes, horseradish and rhubarb. Beware of soggy soil. It can rot bare-root plants.

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