Chilli Thrips

Dale K. Pollet  |  9/30/2009 8:13:28 PM

Chilli thrips no longer an invasive species!

Sciotothrips dorsalis (Hood), the chilli thrip, is a pest of tropical and subtropical regions. Established populations were first found in Florida in 2005, in Houston on landscape roses in 2007 and New Orleans on Knock Out roses in 2009.

The life cycle is similar to other thrip species, such as western flower thrips. Development occurs in 12 to 22 days depending on temperature and host species.

The eggs are inserted into the plant tissue along the veins, terminal plant parts and buds. Hatching occurs in 6 to 8 days under normal temperatures or slightly longer in cooler temperatures. The first two instars actively feed on young, tender plant material, consuming enough plant material to complete development. The third instar has an active and a non-feeding pre-pupal stage that lasts about one day. This non-feeding stage moves to protected areas to pupate on the plant, in the leaf litter or in the soil near the base of the host plant. The pupal stage lasts 2 to 3 days, then the adults emerge. After mating the female can lay from 60 to 200 eggs in her lifetime. The chilli thrip is very small – about half the size of the western flower thrip (Figure1). The adults are pale yellow with dark wings. The abdomen is rounded with dark bands. The antennae are light with the two terminal segments darker. The immature resembles the immature of other species.

Unlike other species of thrips that are flower feeders, the chilli thrips feed on foliage and other plant tissue (Figure 2). Feeding injury causes leaf, bud and fruit bronzing. Damaged foliage curls and becomes distorted and will fall from the plants (Figure 3). New growth on infested plants becomes stunted or dwarfed and appears deformed (Figure 4). Damaged buds become brittle and drop (Figure 5). Young plant material is desired, but all plant foliage above ground is susceptible.

Management of infestations is easier if populations are detected early before they severely damage the plant material. Discoloration of the foliage is the first symptom noted. Where there is concern about an infestation, take a sample of the young growth, put it in a sealable bag and send it in for identification. Do not send the damaged tissue because the populations prefer the new, tender foliage to feed on. Populations can be managed, and different management tools are available for different systems. It is important to rotate the materials used to ensure control and reduce the potential for resistance.

The homeowner is limited at this time to just a few materials, but additional products should be available next year. At present, three materials are available and very functional. Acephate (Orthene), Imidaclorpid and Spinosad are the best controls. All can be applied as foliar sprays, and Imidaclorpid can be drenched. The commercial nurseryman and landscape maintenance personnel have these three plus Tristar, Safari, Flagship, Celero and Avid. Greenhouse growers have these plus three additional materials, Aria, Pylon and Overature. The last two products are greenhouse only.

You may notice no pyrethroids are listed. They are not effective on the thrips and can reduce the beneficial populations that assist in the pest management program. The soft insecticides like the soaps are not effective on the chilli thrip. Rotation of materials and coverage are essential for effective management and assurance of a variety of usable products to manage this pest.

Movement of this pest is through infested plant material. Populations have been found in retail outlets and on berries in grocery stores. The adults are poor fliers, but the host list is extensive with over 250 ornamentals, cotton, vegetables, fruits, citrus and berries. Watch what you purchase we are the primary means of distribution of this pest.

 Dr Scott Ludwig at Texas A & M contributed information to this article.

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