Proper identification of thrips species within greenhouse crops is becoming exceedingly important with the increase in global trade and with climate change allowing species to expand their ranges. Western flower thrips was thought to be the dominate thrips species in greenhouse ornamental crops since the 1990’s. Although this is still the primary thrips pest in most crops, outbreaks of species such as onion thrips, chrysanthemum thrips and Thrips parvispinus necessitate growers needing quick identification tools. As thrips are much smaller than other greenhouse pests such as aphids and whiteflies, a microscope and more comprehensive guides are needed for proper identification. To facilitate growers doing this themselves, rather than continuously sending samples to consultants or government agencies, we’ve developed a simplified key to thrips species known to occur in Ontario. This key has been grower tested and has been widely adopted by IPM practitioners in Ontario.
You can find our Simplified Thrips Key for Growers to help you identify thrips on your farm here: https://onfloriculture.com/thrips-id-key-for-growers/
Who is this Key Designed For?
This key was designed for use by growers of, and IPM practitioners in, greenhouse floriculture and vegetable crops in Canada.
What is the purpose of this key?
For greenhouse growers/IPM practitioners to easily and properly identify species of thrips infesting their crops without necessitating the use of outside identification services.
Proper thrips identification is important because A) the presence of some thrips species can threaten exportation of plant material (e.g. Chili thrips), and B) effective control measures can vary considerably by species. For example, onion thrips and chrysanthemum thrips are both usually susceptible to Success (spinosad), while western flower thrips is not. On-site identification means that proper control or eradication measures can be implemented more quickly.
Collecting thrips for identification:
Collect thrips using plant taps from multiple areas (randomly selected) to get a picture of the entire thrips population in your greenhouse, or from specific areas of concern. Thrips can be tapped directly into a shallow container of soapy water to kill them. Or, thrips can be tapped into a container with a lid, which can be placed in the freezer for at least 30 min to kill the thrips.
Thrips are easiest to examine under the microscope when dead, but not dried out. Therefore, samples should be identified within the next 48h after collection so the samples do not desiccate.
Light coloured thrips can be identified to species on sticky cards, although some of the features may be more challenging to see. Dark coloured thrips are very difficult to identify on sticky cards so it is best to only try to identify them using specimens collected from plant taps.
How to use this key:
All features used in this key can typically be seen using a mid-quality dissection microscope. Your microscope will need to have a maximum magnification level of at LEAST 45X. To determine the maximum level of magnification on your microscope, take the highest number on the adjustable magnification dial (e.g. 4.5) and multiply it by the magnification of the eyepiece (usually 10X).
For each numbered step (1-15), pick one of the two possible choices that most resembles your specimen. This will indicate the species OR the next step you should jump to.
For proper identification, ADULT (i.e. usually winged) thrips must be used. If none of the thrips in the sample have wings, they may be a wingless species. In this case, choose the largest thrips in the sample which have large eyes, a distinct head, thorax and abdomen (see Fig. 1). Larval thrips will appear more “tube like” without distinctive body parts and have small eyes.
Position the thrips stomach side down so that the wings and eyes are facing up, with the head facing away from you. This is often easier to do with a small probe or fine paintbrush with the thrips floating in
water (or 70% alcohol) in a Petri dish or other small clear container. Look at multiple specimens (minimum of 20) to confirm your identification for an infestation on a specific crop. To get a wider picture of your greenhouse population, at least 100 thrips should be identified.
NOTE: This key is NOT comprehensive for all thrips species that may occur in Canada (or that may be found on imported on plant material), but includes those most likely to be encountered in floriculture and/or vegetable greenhouses. If proper species identification is in doubt, please contact an OMAFRA IPM extension specialist, or the National Identification Service.
Who was this key designed by?
This key was a collaboration between Dr. S. Jandricic at the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) and A. Summerfield at the Vineland Research and Innovation Centre in consultation with Eric Maw of the Canadian National Collection of Insects, Arachnids and Nematodes.
Where to find more information:
To see photos of the most common pests found in greenhouses, along with descriptions of their damage and host crops check out our article in Greenhouse Canada:
https://www.greenhousecanada.com/meet-the-new-thrips-on-the-block/
If you are looking for more detailed keys or those that cover more species, there are several keys available online:
http://journals.fcla.edu/flaent/article/view/87973
https://content.ces.ncsu.edu/insect-and-related-pests-of-flowers-and-foliage-plants/thrips-in-the-greenhouse
https://keyserver.lucidcentral.org/key-server/player.jsp?keyId=26&thumbnails=true