Unknowns appear about insects that neonicotinoids control

Thursday, February 5, 2015

by BETTER FARMING STAFF

As the Ontario government moves towards its goal of reducing neonicotinoid seed treatments on corn and soybean crops by 2017, preliminary findings from a massive Ontario study are revealing how little is known about the insects the pesticide has been used to control.

The four-year study, spearheaded in 2014 by the Ontario Soil and Crop Improvement Association, the University of Guelph and the Ontario Ministry of Agriculture, Food and Rural Affairs shows, for example, that the relationship between wireworms and soil type is not as clear cut as researchers initially thought.

photo: Allan Mol

Such knowledge gaps demonstrate why it’s important to get cracking on the research, said Allan Mol, Ontario Soil and Crop’s outgoing president, on Tuesday.

“None of these things have really been studied in the past,” Mol said. “Somehow the government came up with an 80 per cent reduction requirement over the next three years. But right now (with the knowledge gaps), how do we choose that as the number we should be shooting for? That’s why there is a need for this kind of study and more study.”

Mol credited University of Guelph plant agriculture professor Art Schaafsma for motivating the association to undertake the study.

Launched last spring, the study collected data from corn plots across the province with one of the goals being to better understand the insects neonicotinoid seed treatments are used to control in order to develop high risk maps. These include grubs such as European Chafer, June beetle and Japanese beetle as well as other insects such as wireworms, seed corn maggot, corn rootworm, black cutworm, bean leaf beetle and soybean aphids.

Another study goal is to determine how the decision to use or abstain from the seed treatments affects a crop’s outcome and, ultimately, the farmer’s economic bottom line.

Each trial had to contain six plots, half of which used seed treated only with a fungicide and the other half using seed treated with both a fungicide and neonicotinoid, said Jocelyn Smith, a University of Guelph research associate, field crop pest management, who is coordinating the project.

There were 99 locations, 77 of which were located on commercial farms and 22 at Ontario Corn Committee trial sites. Of these, the researchers now have workable data from 63 of the farmer sites. Harvest data has not yet been reported from the OCC performance trial sites, Smith said.

While it’s far too early on to discuss yield results, Smith said assessment of the sites and their soils — researchers visited the sites five times in the growing cycle — revealed that 32 per cent of the locations had wireworms and 25 per cent had grubs. Both were found at 13 per cent of the sites and either one or both were found at 44 per cent of the sites.

The most abundant wireworm species of the seven found was the eastern field wireworm, which made up 58 per cent of the different types of wireworms.

“We’re finding these wireworms all over the place, and the soil type isn’t as clear cut as we thought it would be,” Smith said. There may be a relationship between wireworm species and soil type, she added.

She noted that all the species found were documented economic pests of cereals and corn as well as many other crops. There is some old data from the U.S. cornbelt and Michigan about the different species, but not a lot of literature or research has been conducted into which soil types each of the species prefers.

There are also gaps in knowledge about the life cycles of a number of the wireworm species, she added. Smith said while they were once a concern, over time their numbers decreased and “people stopped caring about them.”

Some U.S. researchers speculate that the introduction of organochlorine pesticides such as DDT controlled the populations and caused the decline.

It’s also being hypothesized that the pesticides stayed in the soil for a long time and have only recently begun to break down. As they disappear, wireworm populations are “making a bit of a comeback,” she said.

“So that’s why we’re concerned about wireworms.”

Smith said researchers would like to introduce plots with soybeans this year using the same approach as had been done with corn, and also to follow the crop rotation in the same fields studied last year. As well, researchers hope to recruit more growers.

Tracey Baute, OMAFRA field crop entomologist, who is also involved in the study, said she can’t stress how important it is to pursue the research: “This is our best way in better strengthening our understanding of these pests so that those growers who do need it (neonicotinoid seed treatment) still have access to the product and we fully understand where they’re going to be and the risks involved so that you don’t deal with yield loss and crop loss.”

The provincial agriculture ministry in partnership with Grain Farmers of Ontario and the University of Guelph Ridgetown Campus recently published a Guide to Early Season Field Crop Pests.

Smith noted that participants in the study would receive reports on the performance of the plots on their own land by the end of the month.

Of 14 local chapter resolutions that were addressed during the association’s meeting, six dealt with the province’s proposed neonicotinoid seed treatment regulation. All were passed.

The resolutions ranged from ensuring the association continues and expands the trials to calling on the federal Pest Management Regulatory Agency to fast track alternatives for pest control.

One resolution from the Middlesex chapter called for the association to ask provincial officials to consider the environmental and economic long term consequences of the strategy, introduce a similar ban on non-field crop uses of the pesticides, including on pet flea collars, and to “fully compensate growers for all crop losses that are verified by an independent third party and are a direct result of the mandatory reduction in use of neonicotinoid seed treatments.”

The number of resolutions tackling the neonic issue shows “it’s right on the front burner with a lot of farmers,” Mol said. BF