Description

Adult Description: Chilli Thrips (Scirtothrips dorsalis) are approximately 1 mm in length, and pale yellow in color. Adults have dark wings and dark bands across their abdomen. Although other flower thrips are also a pale yellow color, chilli thrips are approximately half their size. Adults are so small that they must be mounted on a slide and viewed under a microscope for accurate identification.

Larva Description: Very small, typical-looking insect larvae. Very difficult to identify.

Host Plant: Scirtothrips dorsalis is a polyphagous species with more than 100 recorded hosts from about 40 different families.

Ecological Threat

Before its detection in the continental U.S., Chilli Thrips were considered a serious economic pest in Asia and Australia where it attacked crops such as strawberries, tea, citrus, cotton, soybeans, chilies, castor beans, peanuts, and roses among others. Chilli Thrips prefer young leaves, buds, and fruit. Typically axillary leaf branches tend to be the most damaged. In contrast to Western Flower Thrips Frankliniella occidentalis, Chilli Thrips do not feed on flower pollen.

Common damage includes browning, bronzing or blackening of infested plant parts, stains and scars may also occur. Severe infestations may result in deformation, leaf distortion, defoliation, stunting, and dwarfing. Feeding may cause buds to become brittle and drop.

Chilli Thrips possess piercing and sucking mouthparts and cause damage by extracting the contents of individual epidermal cells leading to necrosis of tissue. This changes the tissue color from silvery to brown or black. Chilli Thrips create damaging feeding scars, distortions of leaves, and discolorations of buds, flowers, and young fruits by feeding on the meristems of the host plant's terminals and on other tender parts above the soil surface. A severe infestation of chilli thrips makes the tender leaves and buds brittle, resulting in complete defoliation and total crop loss.

Biology

The life cycle is similar to Western Flower Thrips, with the entire life cycle complete within 14 to 20 days. Average time for life cycle stages includes the following:

Eggs: 6-8 days, 1st and 2nd instar larva: 6-7 days, Pre-pupa: 24 hours, Pupa: 2-3 days

A single female is capable of laying 60 to 200 eggs in her lifetime. Temperature and moisture influence the number of generations that may occur per year. Females insert their eggs inside the plant tissue on/near leaf veins, terminal plant parts and floral structures. Females are capable of reproducing without mating, also known as parthenogenesis.

History

In the United States, USDA-APHIS inspectors at various ports-of-entry have intercepted S. dorsalis 89 times since 1984 on imported plant materials belonging to 48 taxa, and most frequently on cut flowers, fruits and vegetables. In Florida, an infestation of S. dorsalis was first reported from Okeechobee County in 1991, and then from Highlands County in 1994, with subsequent occurrences in 2004, 2005 and 2007 in various counties of Florida and southeastern Texas.

Scientists believe that S. dorsalis originated either in Southeast Asia or in the Indian subcontinent, but it is now widely distributed.

Native Origin

Asia

Current Location

U.S. Habitat: Found on or around plants they are feeding on. Often, Chilli Thrips are found due to the damage on the plant rather than locating the actual thrip.

U.S. Present: In the United States, the Chilli Thrip Scirtothrips dorsalis, is a relatively new, introduced insect pest in Florida and Texas. Data are unreliable as to which counties in those two states have the thrips and which do not. Further, it is likely that the Chilli Thrip may have spread to other regions of North America, but it is too early to know for sure.

Resembles

Resembles other thrips, but is notably smaller than most.

Management

Various biological control agents, including minute pirate bugs, Orius spp. (Hemiptera: Anthocoridae) and entomopathogenic nematodes, Thripinema spp. (Tylenchida: Allantonematidae), have been reported to effectively control field populations of Chilli Thrips. Adults of Orius insidiosus feed on all the life stages of thrips. Because Orius insidiosus also feeds on aphids, mites, moth eggs and pollen, its population does not decline strongly even if thrip populations are drastically reduced. Thripinema species are entomogenous nematodes which parasitize female thrips and make them incapable of laying eggs, leading to the reduction of thrip populations. In addition, they also reduce food consumption of thrips, resulting in limited feeding damage.

When the biological controls fail, some chemical treatments have been proved effective against Chilli Thrips.

References

Amin BW. 1980. Techniques for handling thrips as vectors of tomato spotted wilt virus and yellow spot virus of groundnut, Arachis hypogea L. Occasional Paper. Groundnut Entomology ICRISAT, 80:1-20.
Arthurs S, McKenzie CL, Chen J, Dogramaci M, Brennan M, Houben K, Osborne L. 2009. Evaluation of Neoseiulus cucumeris and Amblyseius swirskii (Acari: Phytoseiidae) as biological control agents of chilli thrips, Scirtothrips dorsalis (Thysanoptera: Thripidae), on pepper. Biological Control 49:91-96.

Ludwig S. 2009. Chilli thrips: a new pest in Texas. East Texas Nursery and Greenhouse IPM Program.

SEARCH Online

Google Search: Scriptothrips dorsalis
Google Images: Scriptothrips dorsalis
NatureServe Explorer: Scriptothrips dorsalis
Bugwood Network Images: Scriptothrips dorsalis

Internet Sources:

http://www.invasivespeciesinfo.gov
http://www.ldaf.louisiana.gov
http://pest.ceris.purdue.edu
http://wiki.bugwood.org
http://entnemdept.ufl.edu

Experts: 
Mike Merchant - Texas A&M University - m-merchant@tamu.edu

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