Homeowners should be on the alert for a small insect called chilli thrips, which feeds on the young, tender parts of many plants, according to Yan Chen, an entomologist at the LSU AgCenter Hammond Research Station.
A pest of tropical and subtropical regions of the world, chilli thrips first made an appearance in Louisiana on Knock Out roses in New Orleans in 2009.
They’re most obvious and prolific on roses, says LSU AgCenter horticulturist Allen Owings. They’re also common on camellias, plumbago and Indian hawthorne, as well as other ornamental plants.
Populations can be high in September and October as temperatures cool off somewhat, Owings says.
“They’re typically seen affecting new growth where plants were pruned in late August and early September or are having their fall growth flush,” he says.
Unlike other thrips species that are flower feeders, chilli thrips feed on foliage and other plant tissue, Chen says.
Feeding causes leaf, bud and fruit bronzing, and damaged leaves curl, become distorted and fall from the plants. On infested plants, the new growth becomes stunted or dwarfed and appears deformed. Damaged buds become brittle and drop.
“Chilli thrips prefer to feed on young plant material, but all plant foliage above ground is susceptible,” Chen says.
The insects are quite small — about 1?25 to 1?8 of an inch long. Nymphs are pale yellow and highly active while adults are pale yellow with dark wings and jump when they’re disturbed. If you suspect chilli thrips, the best way to identify them is to place a sheet of white paper beneath the leaves or flowers and shake the plant. The thrips will fall onto the paper.
Managing infestations is easier if populations are detected early before they cause severe damage, Chen says. For homeowners, treatment can be done with three materials that are available and very functional — Acephate (Orthene), imidaclorpid and spinosad. All can be applied as foliar sprays, and imidaclorpid can be used as a drench.
Chilli thrips are moved through infested plant material. Populations have been found in retail outlets and on berries in grocery stores, Chen says. The adults are poor fliers, but they can be found on over 250 ornamentals, vegetables and fruits.
More information is available online at lsuagcenter.com/hammond.
Got a gardening question? Write to GardenNews@agcenter.lsu.edu.