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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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Flowers in My Back Yard Series

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Aug. 4: Dianthus a deceptively hardy flower

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June 30: Agapanthus adds blue fireworks to the garden

June 23: Easy-care gazanias fill those hot corners

June 16: Daylilies are perfect for water-wise gardens (and a lot more)

June 9: Grow coneflowers for pollinators -- and yourself

June 2: Sunflowers capture Sacramento's summer attitude

May 29: Are your roses going 'blind'?

May 26: Zinnias are the summer flowers every garden needs

May 19: Plant dahlias now for late-summer flower power

May 12: Know your coreopsis from your bidens

May 5: Mums the word on Mother's Day weekend

April 28: Majestic Matilija poppy is worth a look

April 21: Celebrate roses, America's favorite flower

April 14: Small flowers with outsized impact

April 7: Calendulas do double duty

April 3: Make Easter lilies last for years to come

March 31: In praise of a pollinator magnet (small-leaf salvias)

March 24: Azaleas brighten shady spots

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Feb. 24: Treasure spring daffodils now and for years to come

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Feb. 3: Why grow flowers?

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Garden checklist for week of Aug. 16

During this break in the heat, feed your garden. Make sure to water before and after applying fertilizer.

* In the garden, direct seed beets, carrots, leaf lettuce and turnips.

* Plant potatoes.

* Harvest tomatoes, beans, squash, pepper and eggplants to prompt plants to keep producing. Give your plants a deep watering twice a week, more if planted in containers. Also, give them a boost with phosphate-rich fertilizer to help fruiting.

* Watch out for caterpillars and hornworms in the vegetable garden. They can strip a plant bare in one day. Pick them off plants by hand in early morning or late afternoon.

* Feed citrus trees their last round of fertilizer for the year. This will give a boost to the fruit that’s still small.

* Mulch can be your garden’s best friend – it conserves moisture while blocking out weeds. But don't let mulch mound around stalks, stems or trunks. That can promote rot.

* Camellia leaves looking a little yellow? Give them some chelated iron. That goes for azaleas and gardenias, too.

* Pick up after your fruit trees. Clean up debris and dropped fruit; this cuts down on insects and prevents the spread of brown rot. Then feed fruit trees with slow-release fertilizer for better production for next year.

* To prolong bloom into fall, feed begonias, fuchsias and container plants. Always water before fertilizing.

* Fertilize fall-blooming perennials, too. Chrysanthemums can be fed until the buds start to open.

* Prepare for a fall full of flowers by paying a little extra attention to your garden. Cut off spent blooms from roses, annuals and perennials, then give them a boost of fertilizer. Make sure to water plants before feeding. Roses will rebloom about six to eight weeks after deadheading.

* Indoors, start seedlings for fall vegetable planting, including bunching onion, cabbage, broccoli, cauliflower, kale, radicchio and lettuce.

* Sow seeds of perennials in pots for fall planting including yarrow, coneflower and salvia.

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Time to give vegetable seedlings some more space

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How to grow summer salad greens

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Battling early-season tomato pests

Make your own compost

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Your plants can tell you more than any calendar can

Maintain soil moisture with mulch for garden success

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

Should you stock up on fertilizer? (Yes!)

Grow culinary herbs in containers

When to plant summer vegetables

Don't be fooled by these garden myths

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