Greenhouse Canada

Low thrips pressure is an opportunity to experiment

September 3, 2019  By Greenhouse Canada

Image via ONFloriculture

“It’s that time of year again where two of our biggest crops cross over: fall pot mums and poinsettia,” writes OMAFRA’s Dr. Sarah Jandricic in her latest ONFloriculture post. “This means growers have to simultaneously keep an eye on the two biggest pests in the industry: thrips (usually western flower thrips) and Bemisia whitefly.”

Over the past few months, Jandricic’s team has been monitoring several thrips species inside and outside of several mum operations in southwestern Ontario.

“The good news is that all thrips levels (both onion and western flower thrips) seem unusually low right now and don’t show any sign of going up again as temperatures cool,” she writes, which is likely due to a relatively wet spring/summer and effective thrip management inside the greenhouse with methods such as cutting dips.


While low levels of thrips have allowed some growers to reduce their spending on biocontrol, Jandricic cautions that growers should still stick to any plans involving the use of mite sachets and potentially take this opportunity to experiment with different biological treatments.

Jandricic calls this September period the “whitefly tipping point”, where growers must decide whether to continue their biocontrol program in poinsettia or switch to chemical pesticides.

While the season has had a strong healthy start, she notes that whitefly numbers are creeping up, with coloured varieties and earlier cuttings being affected to a greater degree. However, she also notes that parasitoids are also working.

Growers should base their decisions on several factors, including how heavily the main red poinsettia variety has been affected, whether the biocontrol program is working, whitefly colonization on new growth, and whitefly pressure. For a quick self-assessment, read her article here.

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