Posted 18 December 2007. PMN Crop News.
Chilli Thrips Invade Texas Landscapes, Gardens
Texas A&M University. coals.tamu.edu
Overton, Texas (December 7, 2007)--Home gardeners throughout the southern U.S. need to be on the lookout for a new pest that attacks many popular landscape plants, say Texas Cooperative Extension experts.
The pest is called chilli thrips, which is a somewhat misleading name as the insect feeds on many plants other than just peppers, said Dr. Scott Ludwig, Extension entomologist and integrated pest management specialist.
"It's not going to go through the landscape and eat everything, but it is known to attack plants in 40 plant families, including many foundation plants in the landscape," said Ludwig, who is a member of a national chilli thrips task force.
Susceptible landscape plants include roses, ligustrum, lisianthus, pittosporum, herbs including sweet basil, begonia, and Indian hawthorn.
"There are others, but in Florida, where the pest was discovered two years ago, these are plants where it is commonly observed," Ludwig said.
The pest significantly changed how Florida landscape companies provided pest-control services, Ludwig said. "Though the pest is easily killed with certain insecticides, we have not found any insecticides that provide long-term preventive control," he said. "The landscape companies found themselves spraying every two or three weeks – whenever the plants had a new flush of growth." The pest is mainly a forage feeder, preferring new leaves and buds. Unlike aphids, another common plant pest, chilli thrips do not use a proboscis to puncture a plant and suck out juices. Instead, they use a "rasping" motion to wear away the outer tissue of leaves and buds, Ludwig said. Then the thrips suck sap from the wound. This feeding action causes a distinctive brownish-bronze discoloration in leaves and buds.
The damage is often more than just unsightly. Damaged rose buds, for example, will yield misshapen flowers or fail to bloom.
The pest is not just a risk to home gardens and landscapes, Ludwig said. It poses a substantial risk to cotton, peanuts, grapes, tomatoes and hot peppers. The introduction of the pest in Texas has been traced to garden centers that import plants from out of state. For this reason, it is most likely to become a problem in ornamental landscapes. The pest was recently found on landscape roses in Houston.
It's no surprise chilli thrips were detected in roses first, Ludwig said. Roses are a very popular landscape plant in Texas. Growers of the older, traditional rose lines will probably not have to worry though, he said. This is because the older varieties require frequent spraying, and the same controls used for other insect pests on roses will control thrips too.
However, newer varieties of roses that do not require frequent spraying may be damaged by chilli thrips, he said.
And Ludwig doesn't recommend preventive spraying. "What you'll most likely do is kill beneficial insects: the same ones that offer some control of thrips and other pests," he said.
The pest is about 2 millimeters or little more than one-sixteenth inch long and hard to identify by anyone except a professional entomologist. Instead, it's better to carefully monitor plants for signs of damage the pest causes, Ludwig said.
Extension and the national task force to which Ludwig belongs are trying to develop control recommendations – particularly long-term controls – for the pest, he said. Because thrips, like any other insect, will adapt to different environments quickly, Extension entomologists need to track the spread of the pest through Texas.
Home gardeners who think they may have an infestation may get help one of two ways, Ludwig said. One way is to contact the Extension office in their county. Contact information can be found on the Internet at county-tx.tamu.edu. Or they may visit a Web site that Ludwig maintains at chillithrips.tamu.edu.
The Web site has contact information as well as pictures to help identify chilli thrips damage and ways to control the pest.
Ludwig emphasized that home gardeners shouldn’t start spraying just because they suspect they have chilli thrips.
"More often than not, indiscriminate spraying does 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.
"There are many things that mimic thrips feeding damage, including herbicide damage, some diseases and broad mites."