Chilli Thrips, Vol. 10, No. 06
Scirtothrips dorsalis
Order: Thysanoptera
Family: Thripidae
“Something is terribly wrong with our roses! They look like they have been sprayed with herbicide. The leaves and blooms are all brown and distorted. We have not had a decent bloom in weeks and some plants have lost over half their leaves.”
Thrips are our smallest insect pests, with adults of common species being less than 1/16 inch long. Chilli thrips are small even for thrips, less than 1 mm (1/25th inch), but these tiny insects can cause big problems on roses, peppers, and many other plants.
This non-native thrips first appeared in Florida in the 1990s. It has spread since then, especially in the nursery trade. First detection in Mississippi was in 2014, in greenhouse and nursery settings. More recently, chilli thrips has begun to appear in landscapes around the state, especially rose gardens. Fortunately, such infestations are still relatively uncommon, but incidence is likely to continue to increase, and it is important for gardeners to be aware of this new pest and the damage it causes.
Chilli thrips attack more than 200 species of plants, but roses and peppers are especially susceptible. Adults and immatures use piercing/sucking mouthparts to feed on young developing leaves and buds, and damage is magnified as leaves and petals expand. Take a sheet of paper, fold it in half, fold again, again and again, punch a couple dozen holes with a hole punch, unfold the paper, and you will get the idea. Heavily damaged blooms will have brown edged petals and not open properly; heavily damaged leaves with be curled, distorted, and covered with dark-colored lesions. Other plants that can be damaged by chilli thrips include strawberries, blueberries, tomatoes, eggplant, Indian hawthorne, hydrangea and many more.
Fortunately, chilli thrips do not survive exposure to prolonged severe winter temperatures in landscapes, but the limit of this winter survival is still being determined, and chilli thrips can survive short-term exposure to sub-freezing temperatures. This means a rose planting that was infested in North Mississippi last year may not have thrips survive the winter to reinfest this year, but only time will tell.
Scout for chilli thrips by becoming aware of how damage looks on plant species you grow—by checking out photos of damage. If you suspect damage, use a hand lens to look closer. Chilli thrips are small, but they can be seen under a hand lens. Another method is to beat plant parts suspected of harboring thrips against a stiff piece of white cardboard or similar surface and check for dislodged thrips.
Control: The first line of defense is to avoid bringing infested plants into the landscape or carrying chilli thrips through the winter in a greenhouse or on indoor plants, such as poinsettia, schefflera, gerbera, etc. Unfortunately, low infestations of these tiny pests are difficult to detect. Being aware and alert for damage symptoms is the next defense. The sooner infestations are detected and treated, the better the control.
Several insecticides are effective against chilli thrips, but none can be counted on to give 100% control with a single treatment. Spinosad (FertiLome, Monterey, Bonide and others) is one of the more effective foliar sprays. Other foliar sprays include: acephate (Bonide Systemic Insect Control), acetamiprid (Tristar) and abamectin (Avid and Minx 2). Some of these are only available in commercial quantities but are useful for serious hobbyists with large numbers of plants. On roses, removing, bagging, and discarding buds and blooms before spraying will improve control—because you are discarding thrips hiding in protected areas where your spray will not reach. Soil or pot drenches with products containing imidacloprid are especially useful and provide longer-lasting control than foliar sprays, but effective control will require a combination of treatments.
For more information see: Kumar, et. al. 2009, Featured Creatures, Chilli Thrips, U. Fl.
Thanks to Tracy Kramer for sharing this photo of chilli thrips damage on rose.
Blake Layton, Extension Entomology Specialist, Mississippi State University Extension Service.
The information given here is for educational purposes only. Always read and follow current label directions. Specific commercial products are mentioned as examples only and reference to specific products or trade names is made with the understanding that no discrimination is intended to other products that may also be suitable and appropriately labeled.
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