It's no longer a matter of conjecture, said a Texas AgriLife Extension Service expert. Chilli thrips are here and if left untreated, an infestation at a bedding plant or nursery operation could cost the grower his or her entire season's production.
"They're in the landscape. Ornamental and all agricultural producers need to be concerned too," said Dr. Scott Ludwig, AgriLife Extension entomologist and integrated pest management specialist.
"What I'm telling growers is that if they're seeing damage that they've never seen before, send a sample in," Ludwig said.
Chilli thrips -- tiny insects less than a sixteenth of an inch long – are known to attack at least 40 plant families, including many landscape plants. In Texas, they have been identified on cleyera, acuba, red maple, Japanese maple, live oaks, pomegranate, roses, ornamental sweet potatoes, begonias and many other ornamentals, he said.
"(The pest) has been reported damaging food and fiber crops too, including vegetables, blueberries, cotton and peanuts," he said. "The most common plants we've seen them on so far have been roses – all types, including types that were previously thought to be tolerant to pest problems."
Chilli thrips are thought to have entered the U.S. via the Carribean but originated in Southeast Asia. Last year in Texas, they were only found in the Houston area. Now the insect has shown up in eight counties, including Bexar (San Antonio) and Van Zandt (East Texas).
And because chilli thrips behave differently than other thrips, they're poised to cause millions of dollars in damage, he said.
Other types of thrips usually only damage the flowering part of roses and other ornamental landscape plants. What makes chilli thrips so potentially devastating is that they attack actively growing parts of plants, leaves, buds and stems, Ludwig said.
"Other thrips feed mainly on the flowers," he said. "The damage may set growers back but they won't lose the crop."
However, because chilli thrips damage the vegetative growth, the whole season's production may be at risk. Worse, as the pest is new to Texas, professional growers and landscape contractors don't recognize the damage as being of insect origin, Ludwig said. By the time they do, plants may be damaged to the point of not being marketable.
For example, in Van Zandt County, a grower thought he had pesticide damage and sent a plant in to Ludwig for analysis. Ludwig, who is one of the lead researchers of a national U.S. Department of Agriculture chilli thrips task force, recognized the damage as being caused by chilli thrips and was able to devise a treatment plan.
"We figured that he would have had $39,000 in lost plant material on 11 species of ornamentals if we had not properly identified the problem," Ludwig said. "That's a big hit for a small grower."
Other growers have had similar experiences where the potential loses have been in the hundreds of thousands of dollars.
"If the growers keep their eyes open and see a hot spot and treat them, they'll be okay," Ludwig said. "The problem is the thrips are not being identified early in the infestation. The plants they're showing up on are ones that growers may not be paying a lot of attention to this time of year."
Another problem is that chilli thrips are attacking plants previously thought to be resistant to pest and diseases, requiring few if any sprayings, such as shrub roses. In reality, because they are such popular landscape plants, Ludwig is seeing many instances of infestation in all varieties of shrub roses, both in the nurseries and home landscapes, he said.
Home landscapes may pose the more difficult areas to control the pest. In a nursery, the operator can treat the whole facility. He or she may have to treat often with the currently approved controls, but it is possible to keep the pest in check, Ludwig said.
However, in a home landscape, if a homeowner or landscape contractor treats one area, there's no assurance that chilli thrips from a neighbor's yard won't be back in a few days.
Ludwig is working to develop integrated pest management techniques specifically for chilli thrips. Integrated pest management, commonly known as IPM, strives to use less chemical pesticides by correct timing of applications, pest identification and biological controls.
At a Houston test site, Ludwig is working with AgriLife Extension agents in Harris County, Harris County Master Gardeners, the U.S. Department of Agriculture's Floriculture and Nursery Initiative, and the American Rose Society. The goal is to test a variety of chemicals and biological control techniques.
More information on chilli thrips and pictures of the damage they do and instructions on where to send plant samples for testing can be found at a http://chillithrips.tamu.edu.
Ludwig emphasized that home gardeners should not start spraying just because they suspect they have chilli thrips. "Indiscriminate spraying" is unlikely to control chilli thrips and may actually do more damage than good, he said.
"Not only will they waste money and risk damaging their plants, they may kill the very beneficial insects that naturally help keep thrips in check," Ludwig said. "Proper identification of the insect and the use of the correct insecticides is the key at this time."