If thrips biocontrol programs don’t seem to be working as well as they used to, it might be because there’s a different thrips in town.
A study conducted by OMAFRA’s Dr. Sarah Jandricic and her team found that over 30 per cent of the thrips species collected from floriculture greenhouses were actually onion thrips (Thrips tabaci). Very similar looking to Western flower thrips, the two are impossible to differentiate with just a hand lens. The highest ratios were found in gerbera and mums (both potted and cut), but outbreaks have been seen in other plant species as well.
This may apply to growers outside of Ontario, as a recent study in France also indicated that up to 47 per cent of thrips in floriculture greenhouses were onion thrips.
Onion thrips should be suspected if clusters of the following symptoms are seen on potted plants: intensive foliar damage, localized damage on a small group of plants, and/or appearance despite good biocontrol coverage. Growers with all or most of the items on this list should refer to this ONFloriculture post, which has details on how to ID thrips species, as well as ways to control them.
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