Confusion exists about the type of seed treatment that should be used to control flea beetles, says a provincial insect specialist.
Scott Hartley of Saskatchewan Agriculture said it depends on what flea beetle species are present and their relative abundance.
Hartley, who presented a study on the evaluation of seed treatments used to control crucifer and striped flea beetles in canola Jan. 12 during CropSphere, said there’s limited information on key factors influencing efficacy as well as on the geographic distribution of flea beetles.
As a result, collecting information and understanding beetle populations are critical to selecting the most appropriate seed treatment.
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“There’s an urgent need to implement a monitoring program for flea beetles in commercial canola fields,” he said.
Hartley said there’s been a major shift in predominant flea beetle species over the last decade.
The crucifer species had been the most common on the Prairies, but field studies are showing that the striped beetles are taking over. Striped flea beetle populations have historically been higher in the canola growing area of northern Saskatchewan, while the crucifer species was dominant in the central and southern regions.
Researchers don’t know why the shift is occurring, but there are two variables to consider.
“It looked like the neonicotinoids weren’t as good on striped as they were on crucifer,” he said.
“If you dropped the one number, the other one obviously will be a higher number.”
Hartley thinks the weather has also played a big role in the shift.
“Really, if you look at climatic conditions, what we’ve had over the last decade since 2003 has been moist cool conditions in southern parts of the province, which are much more similar to what the striped flee beetle area normally was in the past,” he said. “Certainly we’ve had a wetter, moister decade. When I look at degree-day modeling that we’ve done for insects from 2003, we haven’t had anything until this last year.”
Farmers now have control options beside neonicotinoids.
“As of 2014, with the new input with the diaimide class of chemistry, it’s something that’s given an added tool to be able to both control striped flee beetle and work under moisture conditions that the neonicotinoids didn’t seem to work as well on.”
- All products performed best in drier conditions and higher temperatures.
- Neonicotinoids are more effective on crucifer flea beetles than striped flea beetles.
- There was no statistical improvements with higher rates of neonicotinoids in most years.
- Higher rates of seed treatments will be advantageous only with very wet conditions or very high flea beetles populations.
