Origin and Distribution
Chilli thrips, Scirtothrips dorsalis (Hood), is an important pest of crops in tropical and subtropical regions. An established population of this pest was first detected in the United States on landscape plants in Florida in 2005. In November 2007, chilli thrips were identified in a residential landscape in Houston, TX. By the summer of 2008, chilli thrips had been identified throughout the Houston area.
Adult chilli thrips
Chilli thrips are extremely small and difficult to distinguish from other thrips species without the aid of a good hand lens or compound microscope. Adults are pale with dark wings and less than 1 mm in length. Immature chilli thrips are also pale in color and resemble the immature stages of many other thrips species.
Chilli thrips damage on rose foliage
Description of Feeding Damage
Infestations by chilli thrips are usually first detected in the landscape by their distinctive feeding damage. Unlike flower thrips, which feed primarily on pollen, chilli thrips feed on various plant tissues. Feeding causes bronzing (tissues turning bronze in color) of leaves, buds, and fruit. Damaged leaves may curl upward and appear distorted. Infested plants become stunted or dwarfed and leaves may detach from the stem at the petioles in some plant species. Feeding may also cause buds to become brittle and drop. Young leaves, buds and fruits are preferred, although all above-ground parts of host plants may be attacked.
Chilli thrips have a very broad host range and may feed on many of the common plants found in Texas landscapes. All broadleafed plants should be considered potential hosts for this thrips (Table 1).
Chilli thrips damage on Indian hawthorn foliage
Plant Monitoring and Identification
Plants with the symptoms described above should be examined closely for the presence of thrips. Thrips collected from the leaves or buds of plants with suspected damage should be collected and properly identified. If you wish to participate in efforts to monitor the distribution of this pest in Texas, place samples of thrips or suspected thrips-infested plant parts into a Ziploc bag, add a dry piece of papertowel or napkin to avoid excessive moisture, and seal the bag. Label the bag with collection information including locality (city or town and county), date, species of host plant, and your name and contact information. Send samples via express mail (next-day delivery) to assure good sample quality. Through the end of 2009 please send samples to: Chilli Thrips Lab, Texas AgriLife Extension Service, P.O. Box 38, Overton, TX 75684.
There are a number of insecticides available to manage this pest (Table 2). It is important to remember that chilli thrips attack developing terminals and buds. The best time to treat a plant is while it is actively growing. Thrips generally leave damaged plants with stunted or severely slowed growth.
Treating the soil of infested plants has not been effective in most studies conducted to date. Systemic insecticides, therefore, should be applied as a foliar spray.
Pyrethroid insecticides, such as permethrin, cyfluthrin, esfenvalerate and bifenthrin, are not effective against chilli thrips and should not be used, since they are toxic to natural enemies.
Soft products, such as insecticidal soaps, appear to suppress chilli thrips populations. In order for theses products to be effective, they need to be applied on a regular basis. Thrip population have been shown to increase dramatically once applications have stopped.
To prevent insecticide resistance from developing, it is important to rotate insecticides between chemical classes with different modes of action. For example, a product containing spinosad (IRAC MOA Number 5) should be used the first time and then a product containing acephate (IRAC MOA Number 1B) should be used when a second application is made. All the products with an IRAC MOA Number 4A are related and applications should be alternated with either products containing acephate, abamectin or spinosad.
Predators such as the minute pirate bugs, predatory mites and even predatory thrips have shown potential to control chilli thrips in greenhouse studies. We are still evaluating these organisms to understand their use in the landscape.
Chilli thrips damage on hybrid tea roses
To prevent the introduction of chilli thrips into new landscapes it is important make sure that material is not infested prior to planting. New plants being planted could be infesting in a number of ways. The most common method would be to purchase infested plants. However, another overlooked method would be for infested plants removed from the landscape and brought back to a holding area to infest clean plants. When moving plants between properties make sure that they do not have chilli thrips. Infested plants can spread an infestation to holding areas and new landscapes into which they are planted.
Chilli thrips damage on cleyera
Immature (top) and adult (bottom) Franklinothrips vespiformis, a predatory thrips know to feed of chilli thrips in Florida.
The authors would like to thank Chris Sansone, Bart Drees and Mike Merchant for their reviews of this publication. Chemical efficacy results in this publication were funded by the IR-4 Project and United States Department of Agriculture, Agriculture Research Service
Table 1. Plants in Florida on which chilli thrips has been found to reproduce.
|Arachis hypogaea||Peanut or Groundnut (greenhouse)|
|Cuphea sp.||Waxweed, Tarweed|
|Duranta erecta||Golden Dewdrop|
|Eustoma grandiflorum||Florida Blue Lisianthus|
|Ficus elastica ‘Burgundy’||Burgundy Rubber Tree|
|Fragaria x ananassa||Strawberry|
|Gerbera jamesonii||Gerber Daisy|
|Glandularia x hybrida||Verbena|
|Gossypium hirsutum||Cotton (greenhouse)|
|Hedera helix||English ivy|
|Lagerstoemia indica||Crape Myrtle|
|Ocimum bascilicum||Sweet Basil|
|Pelargonium x hortorum||Geranium|
|Petunia x hybrida||Petunia|
|Pittosporum tobira||Variegated Pittosporum|
|Ricinus communis||Castor Bean|
|Rhaphiolepis umbellate||Yeddo Hawthorn|
|Richardia brasiliensis||Brazil Pusley (greenhouse)|
|Salvia farinacea||Victoria blue|
|Shefflera arbicola||Umbrella Tree|
|Tradescatia zebrina||Wandering Jew|
|Vaccinium corymbosum||Highbush Blueberry|
|Viburnum odoratissimum var. awabuki||Sweet Viburnum|
|Viola x wittrockiana||Wittrock’s Violet|
Table 2. Suggested insecticides for control of chilli thrips in the landscape.1
|IRAC2 Mode of
|Active Ingredient||Products||Application Method|
|1Biorational products such as insect growth regulators, soaps and oils are currently being evaluated.
Check the label for specific site uses.2 International Resistance Action Committee publishes updated mode of action classification charts.
For the latest information, see http://www.irac-online.org/ .3Pyrethroids such as cyfluthrin are toxic to natural enemies.
Note: Insecticides labeled for landscape plants should not generally be used on vegetables, unless specifically noted on the label. Failing to follow insecticides labels carefully is illegal and can result in unsafe applications. Always check the product label for the list of plants that may be injured by the pesticide.
Mention of commercial products is for educational purposes only and does not represent endorsement by Texas AgriLife Extension Service or The Texas A&M University System. Insecticide label registrations are subject to change, and changes may have occurred since this publication was written. The pesticide user is always responsible for applying products in accordance with label directions. Always read and carefully follow the instructions on the container label.