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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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GENERAL GARDENING

An article about gardening.

Keywords:

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

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Garden Checklist for week of Nov. 3

November still offers good weather for fall planting:

* If you haven't already, it's time to clean up the remains of summer. Pull faded annuals and vegetables. Prune dead or broken branches from trees.

* Now 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.

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

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

* Plant garlic and onions.

* Keep planting bulbs to spread out your spring bloom. Some possible suggestions: daffodils, crocuses, hyacinths, tulips, anemones and scillas.

* This is also a good time to seed wildflowers and plant such spring bloomers as sweet pea, sweet alyssum and bachelor buttons.

* 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.

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

* For holiday blooms indoors, plant paperwhite narcissus bulbs now. Fill a shallow bowl or dish with 2 inches of rocks or pebbles. Place bulbs in the dish with the root end nestled in the rocks. Add water until it just touches the bottom of the bulbs. Place the dish in a sunny window. Add water as needed.

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

* For larger blooms, pinch off some camellia buds.

* Prune non-flowering trees and shrubs while dormant.

* To help prevent leaf curl, apply a copper fungicide spray to peach and nectarine trees after they lose their leaves this month. Leaf curl, which shows up in the spring, is caused by a fungus that winters as spores on the limbs and around the tree in fallen leaves. Sprays are most effective now.

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