Striped flea beetles are taking over some of the territories once dominated by the crucifer flea beetle and that means farmers may have to change their control methods.
Owen Olfert, a research scientist with Agriculture Canada and operator of the Prairie Pest Monitoring Network, said the species are different and must be treated as such.
“… there’s been a shift in some of the areas from the crucifer flea beetle, which can be controlled with some of these neonicotinoids quite nicely in seed dressings (in) canola, whereas the striped flea beetle is a little more difficult to control using those same insecticide seed dressings,” he said.
A 2008 study released by the University of Alberta predicted the rise of the striped beetle.
And in some areas today, it has become the dominant species, said Keith Gabert, an agrology specialist for the Canola Council of Canada.
“Striped flea beetles seem to be coming more dominant or more predominant in the mix and lately we get reports that most of (the beetles being found) are striped.”
The study, called Differences in Phyllotreta cruciferae and Phyllotreta striolata Responses to Neonicotinoid Seed Treatments, recognized then that the industry was grouping flea beetles as a “homogeneous complex” rather than addressing each species with a different solution.
“With continued extensive use of these neonicotinoid compounds for flea beetle control in canola, population displacement of P. cruciferae (crucifer beetle) by P. striolata (striped beetle) also may occur,” stated the report.
The study concluded that striped beetles were less susceptible to the neonicotinoid treatments being used.
It was the first research to directly compare the two species vulnerability to insecticides.
The study said there could be differences in how each species reacts to other insecticides as well.
Bob Elliott, a research scientist with Agriculture Canada’s ecological crop protection, recently released an abstract on research he carried out with collegues: Evaluation of Seed Treatments for Control of Crucifer and Striped Flea Beetles in Canola.
“We started research five years ago at the request of the canola council when they were getting reports from producers about so-called seed treatment failures,” said Elliott.
He attributes the shift from crucifer beetle dominance to striped dominance to several causes, but neonicotinoid susceptibility is factor one.
“In the registration of these products dating back 2003 to 2005, all the work was done on crucifer flea beetles. There was a tacit assumption that if these products control crucifer beetles, they will control striped flea beetles and other species equally well,” said Elliott.
Without historical data, Elliott is hesitant to use the term neonicotinoid resistance when there could be differences in tolerance to the seed treatments.
Elliott’s research also highlights the cooler, wetter weather conditions of the past few years and earlier seeding dates as contributing factors that favour striped flea beetles over crucifer.
“Higher precipitation is an additional factor that has allowed striped beetles to expand their geographic range and create this so-called shift,” he said.
Striped flea beetles become active two to three weeks before crucifer beetles after overwintering.
“With that earlier activity, by planting early, we could be again shifting this very delicate balance potentially in favour of striped over crucifer,” he said.
The research outlines the risks of classifying the beetles together, and stresses the need for more experiments.
“We can state with some assurance that the neonics provide very good control of crucifer flea beetles, but relatively poor control of striped,” said Elliott.
He added newer chemistries are being developed that should give better control.
“We are now seeing seed mixtures registered. This is really a precedent. We’ve never had it before I don’t think for any other insect pest in Canada, so we’re getting now a combination in seed treatment mixture that contains a neonic for control of crucifer and newer chemistries for control of striped.”
Diamide is a new type of insecticide more commonly recognized as cyantraniliprole, a Group 28, and it has a different chemistry than neonics.
The active ingredient can be found in DuPont’s Lumiderm and Syngenta’s Fortenza, where it is used for cutworms.
Syngenta has recently released a new seed treatment, Visivio, sulfoxaflor, a Group 4c insecticide with a neonicotinoid Group 4a.
Elliott advises farmers to choose the best seed treatment according the pests they are seeing. Farmers can scout and lay out sticky traps to assess which species are in their crop.
“Based on that information, a decision could be made to go with a neonic alone, diamide alone or a mixture of the two,” he said.
There have been six new registrations with the Pest Management Regulatory Agency within the last two years and more expected.
The Western Producer has requested assessments from the agency to determine which species were looked at when they were scientifically evaluating value and efficacy of current registered seed treatments. There was no further information as of press time.
Elliott said other options are not really there for the farmers, but they can get more involved.
“Press the industry; that’s where demand comes from. Ask for more options from seed companies,” he said.