Why is Thrips Identification to Species Important?
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.
Quick and accurate 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.
Why did We Create This Key?
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/
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 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, so they can get answers quickly, and avoid the use of outside identification services.
Collecting thrips for identification:
Collect thrips by tapping plants over a white plastic pan from multiple areas (randomly selected) to get a picture of the entire thrips population in your greenhouse, or from specific areas of concern. You can buy or build your own aspirator to capture live thrips from the pan. Thrips can also 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 the 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). We have created a video to help make choosing a microscope easier.
To aid you in using the key, we have created a series of 3 videos that we recommend you watch. Further written instructions and pictorial aids can be found in the Thrips Identification Workshop Workbook.
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