Watch out gardeners. There’s a new thrip in town – and it’s downright destructive. This pest attacks all kinds of plants, from ornamentals to edibles, stunting their growth and leaving them less than desirable to look at.
Chilli thrips are so small, it’s impossible to detect them with the naked eye. Image Credit Dr. Lance Osborne
Photo Credit: Dr. Lance Osborne
While chilli thrips don’t kill their host plant, they can decimate its appearance.
Photo Credit: Dr. Lance Osborne
The rose leaves on the left show chilli thrip damage, while the leaves on the right are healthy.
Photo Credit: Dr. Lance Osborne
Be sure to check your edible plants, too – chilli thrips can render basil practically useless.
Photo Credit: Dr. Lance Osborne
The new offender to US soil is the chilli thrip, Scirtothrips dorsalis Hood. The damaging insect was first discovered in Florida back in 1991, but no established population was found until it was confirmed on roses in Palm Beach County in 2005. Since then, this pest has been found throughout Florida in both the landscape and at production facilities; in the landscape around Houston, TX; and most recently at two wholesale nurseries in Georgia, according to Dr. Scott Ludwig, Extension Program Specialist III – IPM, Texas AgriLife Extension Service.
What makes this thrip so different from the more typical Western flower thrip is the fact this pest feasts on foliage – especially young leaves. “In Florida, [chilli thrips are] hammering homeowners big time,” Scott says. “They like young, developing tissues, so it’s hitting right there in the growing tips of plants – feeding on developing buds or flowers. And that can completely stunt plants and shut down terminal growth. Flowers can open deformed – or not open at all – and the foliage comes out very ‘crinkly.’”
In fact, it’s this unsightly damage that often tips off an infestation. “When I’ve found this [pest] in retail stores, it hasn’t been by walking around with a hand lens and looking,” Scott adds. “It’s very visible in terms of damage caused on the foliage of plants.”
Unfortunately, by the time the damage is visible, the offending chilli thrip might have moved onto other plants. Because the pest is so small, it’s nearly impossible to identify infested plants early enough to prevent damage. The danger here is that affected plants could unwittingly be shipped around the country to establish new populations. While chilli thrips aren’t likely to overwinter in the colder climates of the North, the region’s warm summer months could allow for several damaging generations of the pest to develop. And just a few generations can decimate the look of a landscape, as well as crop yields.
Researchers have already identified more than 100 chilli thrip host plants, and they’re discovering additional ones as more about this pest is learned. Some common ornamental hosts include camellia, celosia, chrysanthemum, coleus, crape myrtle, dahlia, euonymus, geranium, gerber daisy, Japanese holly, ligustrum, lisianthus, maple, Mexican heather, petunia, pittosporum, poinsettia, rhododendron, rose, snapdragon, sweet basil, verbena, viburnum and zinnia. Orchard crops and other edibles that are susceptible to chilli thrips include asparagus, beans, cashews, cherries, citrus, figs, grapes, habanero peppers, strawberries and tomatoes.
So what’s a gardener to do? The first thing is to look for clean plants, suggests Scott. Don’t buy anything with even slightly damaged foliage or flowers. That means inspecting plants closely and looking for any discoloration (on both sides of the leaves), as well as keeping an eye out for any irregularities – stunted growth, misshapen flowers, etc. Be sure to examine the plants next to the one you’d like to buy, too – if nearby plants show any signs of damage, your plant could have already picked up some hungry guests that could injure it.
And keep an eye out for anything unusual in your garden during your regular pest scouting. If you find anything out of the ordinary that suggests chilli thrip damage, take a sample of the disfigured plant and compare it with online images of thrip damage. Scott also suggests snipping off buds, young growth and flowers, as well as any already-damaged plant parts, and taking the samples to your local Extension Office for examination and proper identification.
The bad news is that there isn’t a recommended control for use against chilli thrips in the landscape yet because this pest is so new, Scott explains. The good news is that there is a wide range of products that have proven effective against this pest in production facilities – although by in large, they don’t translate into use for homeowners. “Right now we strongly encourage people not to use pyrethroids [synthetic compounds found in insecticides] … because they’re hard on natural enemies and don’t seem to touch chilli thrips,” Scott says. “Orthene will work, but that’s a harsh product. If you’re using it to spot-treat a couple of plants, that would be okay. But you don’t want to treat your whole yard with it.”
Researchers are currently looking into softer chemistries for controls, as well as natural enemies of chilli thrips. According to Scott, there are some predatory mites that have shown some control at the greenhouse level, but nothing so far that would keep damage from happening in a yard situation. Another area of study is examining what types of plants chilli thrips don’t affect, but just when researchers think they’ve nailed something down, the thrips start eating at it, Scott adds. Only time and research will tell what works best.
Meanwhile, some homeowners in parts of Florida are ripping out entire plantings because the thrips have decimated their garden. (It’s that, or they’re left looking at unsightly plants until new growth emerges next year.) For now, the best advice out there is to really inspect any plants before you buy them no matter where you live (because remember, plants are shipped around the country). Bringing only clean, healthy plants into your garden is your best chance for keeping your garden in the green and chilli thrip-free all season long.
