Tropical Thrips Species Intercepted on Plant Material in Ontario: Be Aware – But Don’t Panic.

This post was co-written by A. Summerfield (Vineland Research and Innovation Centre) and S. Jandricic.

Figure 1. Thrips parvispinus is generally dark coloured (though the head and thorax can be lighter than the abdomen), has bright red ocelli and clear patches at the top of its wings.

Increases in global trade, along with decreased use of harsher broad-spectrum pesticides makes it easier for insect species to move around the world. Because of this, it is becoming more common to find unusual pests coming in on plant material. It’s important that we are prepared and know what to do when something like a new thrips species makes an appearance.

The tropical thrips species Thrips parvispinus has been popping up in various parts of the globe in recent years and was intercepted on plant material in two Ontario greenhouses in 2021/2022. Read on to learn what we know about this species and what you should do if you suspect you have them.

The New Detection and What happened Next: (Spoiler: not much!)

Two isolated incidences of T. parvispinus were intercepted on crops in Niagara and Leamington in the Fall of 2021 and the Spring of 2022. As this species has been previously detected in Florida and countries in Africa, it is likely that this species came in on imported plant material.

Damage from Thrips parvispinus causes heavy brown streaking on leaves, leaf distortion, and new leaves may not emerge properly.

Identifications were confirmed by taxonomists at the Canadian National Collection of Insects, Arachnids and Nematodes (CNC) at Agriculture and Agri-Food Canada (AAFC) in Ottawa, using DNA barcoding. This level of careful identification is necessary for first finds of any new species in a country or region to prevent misidentification.  

The Canadian Food Inspection Agency (CFIA) then was notified by CNC-AAFC of the new record; this is required under Canadian regulations so early mitigation and eradication efforts can be taken for new pests to protect the industry, if necessary.  

After notification, CFIA determined it was not necessary to take action at this time. This is similar to the first interception of chili thrips (Scirtothrips dorsalis) in Canada in 2018, where CFIA was satisfied as long as appropriate eradication efforts were taken. Thrips parvispinus is also generally considered to be a low pest threat and was taken off the European and Mediterranean Plant Protection Organization (EPPO)’s Alert List in 2001, after first being intercepted in the Netherlands in 1996. (You can see EPPO’s decision note here).

What we know about T. parvispinus

Detailed information can be found in this scientific review article, but is summarized here:

  • COMMON NAME: This species is sometimes called tobacco thrips – but Frankliniella fusca, a thrips species native to North America that can also be found in greenhouses also goes by that name! So we’ll just have to go with Parvispinus for now.
  • HOST PLANTS: Like most thrips, this species can feed on a wide range of host plants. New invasions in Europe & North America have generally been intercepted on tropical plants, such as Mandevilla, Dipladenia, Gardenia, Anthurium, Hoya, Orchids, Ficus, Gerbera and Schefflera. In its native range in Indonesia and Thailand, it is also a pest of many vegetable and fruit crops including peppers (especially chilli), tobacco, eggplant, and strawberry.  Therefore, these crops should also be scouted for unusual thrips species or thrips-like damage, especially if grown in the same greenhouse, propagation facility, or garden centre as tropical plants.
Damage from Thrips parvispinus on Schefflera. Note the heavy brown scarring on the leaf and the unusually small, distorted leaves on the growing points.
  • DAMAGE: Thrips parvipsinus leaves feeding scars on foliage and sometimes fruit.  However, this damage can appear much darker than the usual “silvering” we are used to with western flower thrips. Along with heavy deformation of new growth, they cause extensive brown scarring on foliage of tropical plants. Their damage may be mistaken for extreme broad mite damage. Some reports suggest feeding is concentrated on new growth, and that there may be a lower threshold for this thrips than with other thrips pests, due to heavier damage on crops such as tropical ornamentals and peppers.
  • KNOWN DISTRIBUTION:  Its known distribution includes Indonesia, Thailand, Australia, the Phillippines, Taiwan and Hawaii, with isolated populations in India, Tanzania, and Uganda.  Records of interceptions have been recorded in Florida, Netherlands, Spain, Greece, Germany and France.
  • RISK OF ESTABLISHING: As a tropical species, it cannot survive winters outdoors in Canada, but could become resident within greenhouses if eradication measures are not taken.

What To Do if You Suspect T. parvispinus Is on Your Farm:

Remember – if you hear hoofbeats, DON’T assume it’s zebras! If you see a dark coloured thrips in your crop, it’s most likely you actually have a thrips species that is already common in Ontario (see below).

To help you determine if you DO have a zebra in your greenhouse, the newest edition of OMAFRA/VRIC’s “Thrips Identification Key for Growers” now includes this species.

View and download the new key here:

Key-to-important-thrips-pests-of-Ontario-greenhouses_3rdEd_2022Download

Thrips parvispinus. Photo from Thrips-ID.com

If you’ve gone through this key and think you might have T. parvispinus, have the identification confirmed by an OMAFRA specialist, or send them directly to the CNC lab in Ottawa.

Unfortunately, T. parvispinus looks very similar to a species called Japanese flower thrips (T. setosus) — they can only be properly distinguished using a compound microscope at 400x magnification (most consultants won’t have access to this kind of microscope).

After confirming the identification, work with an OMAFRA specialist or IPM consultant to determine the appropriate course of action to control this pest.  

Control Options for T. Parvispinus

Biosecurity measures are designed to prevent, minimize and control the introduction and spread of plant pests at the farm level. (For more information on developing a biosecurity plan, check out the Floriculture Sector Biosecurity Guide). Scouting your incoming plant material for pests is a key part of practicing biosecurity, and is especially important for plant material coming from parts of the U.S. (e.g. Florida) and other countries where T. parvispinus has already been detected.

Growers may also want to consider implementing dipping programs for tropical cuttings in soaps, oils or BotaniGard to lower the risk of bringing in tropical thrips species. (See this post for information on tolerance and efficacy of dipping different plant species – including Mandevilla – in various reduced-risk pesticides). However, different plant species and varieties should first be tested for phytotoxicity before full-scale dipping procedures are implemented.

If you find T. parvispinus on your farm, there are some control strategies you can implement. However, little research on this species has been published, so it’s important to know that best management practices to control T. parvispinus are still being developed.

As we’ve learned with onion thrips and Echinothrips, the typcial biocontrol strategies that work for western flower thrips may not be as effective on other thrips.

Anecdotal reports suggests that T. parvispinus populations may be suppressed in tropical crops with high rates of predatory mites (think Cucumeris and/or the new Canadian predator, Anystis). This strategy needs further testing to determine the level of control.  Better control of this pest in pepper crops may be achieved with a combination of predatory mites and Orius. Other options for cooler-grown crops could be the predatory bug Dicyphus and the predatory mite Limonicus, both of which operate better at lower temperatures than other natural enemies.

On the pesticide front, one laboratory study indicated that T. parvispinus are susceptible to Success (Spinosad), but not to the neonicitinoid Tristar (acetamiprid) (Murai et al., 2010 – see below for full reference). This study has been confirmed in the field – the operation with the first incidence of T. parvispinus was able to get on top of the issue with several drenches of Success before shipping. Drenching Success, rather than spraying it, can be less harsh on your predatory mite population, allowing them to work in concert.

Because this species is on the USDA-APHIS “Pests of Concern” list, eradication with pesticides should always be attempted before shipping plants to the U.S. Scouting should be done before and after applications to make sure pesticides were effective.

Other pesticides that generally show good efficacy for several thrips species include Beleaf, Ference, Pylon, Avid, Kontos, Orthene and Lorsban. Pesticides which are hard on biocontrol agents and have moderate-to-long (3-12 week) residual times should be applied in a separate area to prevent long-term effects on biocontrol in the growing compartment.

OMAFRA is currently gathering information from other countries, and we are hoping to speak with growers who may have encountered this pest to gather more information on what works best.

Common species T. parivispinus are likely to be confused with:

Dark morphs of western flower thrips – head and thorax yellowish in colour, ocelli dull red, long coarse hairs on top of pronotum and head, wings uniform in colour. Dark morphs are more common in late fall/winter.
Dark morph (bottom specimen) of Thrips tabaci (onion thrips) – ocelli are grey (often hard to see), wings uniform in colour. Dark morphs are more common in late fall/winter.
Frankliniella fusca (also known as tobacco thrips) – uniformly dark in colour, ocelli dull red (often hard to see), long coarse hairs on top and bottom of pronotum, wings uniform in colour or wings absent.
Poinsettia thrips (Echinothrips americanus) – body black, red pigment between segments, white patches at top of wings (look clear when in ethanol).
Frankliniella setosus (Japanese flower thrips) – dark body, bright red ocelli, white patches at top of wings (look clear when in ethanol), no long, course hairs on the top of the pronotum or head.

References:

Murai, T., Watanabe, H., Wataru, T., Adati, T and Okajima, S. 2010. Damage to vegetable crops by Thrips parvispinus Karny (Thysanoptera: Thripidae) and preliminary studies on biology and control. In: Persley D, Wilson C, Thomas J, Sharman M, Tree D. (eds). IXth International Symposium on Thysanoptera and Tospoviruses, 31 August- 4 September, 2009. Journal of Insect Science. 10:166 (available
online: insectscience.org/10.166.)

V. SRIDHAR, P. SREE CHANDANA and R.R. RACHANA. GLOBAL STATUS OF THRIPS PARVISPINUS (KARNY, 1922), AN INVASIVE PEST. The J. Res. PJTSAU 49(4) 1-11, 2021.

Leave a Reply