Chilli thrips take aim at floriculture

Recently, chilli thrips, Scirtothrips dorsalis, have been an issue for greenhouse growers. Here is a primer to help you know how to protect your crops.

Background. Chilli thrips were first detected in Highlands County , Fla. , in 1991, although they were not established yet. Chilli thrips was detected on roses from Palm Beach County , Fla. , in 2005. As of January 2007, chilli thrips have been detected in the landscape in Florida from Alachua County to Monroe County and on vegetable transplants and container roses in retail stores in South Texas . In the Western Hemisphere, chilli thrips have been detected in Hawaii and in the Caribbean, including Barbados , Jamaica , St. Lucia , St. Vincent, Tobago and Trinidad .

Host plants. Chilli thrips is a polyphagous species and has been documented to attack more than 100 host plants from 40 families. As this pest expands its geographical coverage, more plants are added to its host range.

Here are some ornamentals: Castor bean, celosia, chrysanthemum, coleus, dahlia, euonymus, geranium, gerbera, camellia, ligustrum, lisianthus, Mexican heather, petunia

pittosporum, poinsettia, snapdragon, verbena and zinnia.

What to look for. Field identification of chilli thrips is extremely difficult and often times impossible to differentiate from other thrips. Adults have a pale body with dark wings and are less than 2 millimeters long. Immature chilli thrips are pale in color as are the immatures of many other thrips. Here are some distinguishing characteristics, which can be found on most life cycle stages.

* Antennae are eight-segmented with segments I–II pale, III–VIII dark.

* Head is pale in color with three pairs of ocellar setae. One pair of ocellar setae are between the hind ocelli. One pair of long postocular setae are behind the hind ocelli.

* Brown antecostal line and brown area behind line in median 1/3 of abdominal tergites.

* Abdominal sternites have brown antecostal line near anterior margin.

* Forewings are brown, paler distally.

* Abdomen has numerous fine microtrichia.

Life cycle. Life cycle is similar to that of western flower thrips. Females insert their eggs inside plant tissue and hatch in six to eight days. The females oviposit 60 to 200 eggs in their lifetime. The immatures pass through two larval stages (first and second instars) that last six to seven days. During this time they actively feed on the host plant. The thrips then pass through a prepupal (24 hours) and pupal stages (two to three days) during which time they do not feed. They can complete their life cycle in 14–20 days.

Damage symptoms. Chilli thrips is mainly a foliage feeder. Young leaves, buds, flowers and fruits are preferred, but all aboveground plant parts may be attacked. Feeding damage turns tender leaves, buds and fruits bronze. Damaged leaves curl upward and appear distorted. Feeding on buds may cause them to become brittle and drop. Infested plants become stunted or dwarfed, and leaves with petioles detach from the stem, causing defoliation in some plants.

Diagnosing. Plants with the symptoms described should be examined for thrips. Place leaves or buds from symptomatic plants into a sealed plastic bag to prevent the thrips from escaping. Label the bag with collection locality information, host plant, date collected and name of collector. Samples should be sent next-day delivery to a diagnostic lab for identification.

Virus vectoring. Chilli thrips has been reported to potentially vector many important plant viruses, including peanut necrosis virus, peanut chlorotic fan virus and tobacco streak virus.

Controls. Not enough is known about chilli thrips to provide comprehensive integrated pest management recommendations. The best control recommendation is to use products registered for your specific operation and are known to be effective against thrips.

Research conducted by myself and entomologist Lance Osborne at the University of Florida suggests that Orthene, Avid, Spinosad, Pylon (indoors), Safari (foliar), TriStar, Flagship (foliar), Aria and the predatory mite Amblyseius swirskii are effective for ornamentals. Trials are being conducted in Texas to evaluate these and additional products. Rotate insecticides used. There are very few insecticides registered for use against western flower thrips or chilli thrips. If you need to treat for chilli thrips, take into consideration what products you have been applying for western flower thrips. If Conserve, Pylon and other insecticides are overused, their effectiveness may diminish and some chemical options needed to manage thrips will become unavailable.

- Scott Ludwig

Scott Ludwig is extension program specialist-IPM, Texas Cooperative Extension, (903) 834-6191; swludwig@ag.tamu.edu.

APHIS establishes task force

USDA’s Animal and Plant Health Inspection Service has created a Chilli Thrips Task Force in response to growing concerns over the recent detection and spread of Scirtothrips dorsalis. The task force includes three components: an Industry Group, an Interagency Group and a Technical Working Group.

The Technical Working Group is comprised of university and government researchers.

Entomologists Lance Osborne of University of Florida and Matt Ciomperlik of APHIS are co-chairs of this task force.

A National Pest Alert on chilli thrips has already been developed. It has been published and sent to many of the potentially impacted states.

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For more: Lance Osborne, University of Florida , Mid-Florida Research and Education Center , (407) 884-2034; lso@mail.ifas.ufl.edu. Matt Ciomperlik, APHIS; (956) 580-7228; matt.a.ciomperlik@aphis.usda.gov.