Beneficial organisms | Neonicotinoids are useful, says researcher, but have been overused by farmers
RIDGETOWN, Ont. — The proposal to limit the use of neonicotinoid seed treatments in Ontario may be a positive development for the farmers using them, according to a Purdue University entomologist.
Based on the studies he has seen, Christian Krupke said the yield advantage from neonicotinoid seed treatments is inconsistent at best.
Another important consideration is the impact the chemicals have on beneficial insects and soil microbes.
Krupke cited research at the John Tooker Lab at Pennsylvania State University as an example. Farmer-friendly ground beetles were provided with slugs that had been consuming soybean plant material containing neonicotinoid residue. While the slugs were unaffected, the ground beetles are poisoned, many dying within half a day.
“Neonicotinoids are used for all the crops in various forms with the exception of forages,” Krupke said.
“I think in agriculture we need to ask the question: is this the best we can do? I don’t think putting these on every corn seed is the best we can do. … These are useful tools but we also have to be careful using them. Using a pesticide everywhere on a crop all the time, we have never had good outcome with that.”
According to Tooker, relatively high levels of neonicotinoids were used in the experiment.
However, he said he thinks the same type of ground beetle impact is likely in a field setting.
Krupke spoke at the University of Guelph’s annual diagnostic day, along with Tracey Baute, an entomologist with Ontario’s agriculture ministry.
“Make no mistake, things have to change and the Pest Management Regulatory Agency has been saying that for a year. Current rates (of neonicotinoid seed treatments) are not sustainable,” Baute said.
The chemicals are useful but do not result in a yield advantage in all instances. With field corn, for example, 10 to 30 percent of the acreage in Ontario may be at risk of yield-robbing damage.
Research is underway this year to learn more. Comparisons are being made at about 100 different locations between corn grown from seed with insecticide and fungicide and corn grown from seed with fungicide only, Baute said.
The challenge for researchers and farmers is to determine which fields are likely to be at risk.
Baute and Krupke said farmers should also consider the length of time seed is protected from soil-borne insect pests.
Detectable levels remain on corn seed for about 10 days and for 18 days on soybean seed, Krupke said.
However, by the end of those periods, insecticide levels are likely too low to affect insects eating the seed.
As far as the systemic effects — insecticide taken up by plants — these are limited, Krupke said.
“It’s actually an inefficient way to get pesticide into the plant. With corn it’s about five percent,” he said.
“With beans and corn, the plants are not protected for very long. I think they (the treatments) have been oversold.”
Art Schaafsma, field crop pest management specialist with the University of Guelph, said he fears Ontario may move away from a science-based, decision making process to address the issue of neonicotinoid seed treatments.
“What we’re asking is, can science have some time to sort this out,” he said.
“In my opinion there are two things going on. There’s an acute impact involving the dust. The solution to that is to put the dust into the ground. The other issue is how much these insecticides are being used and where they’re going to in the environment.”
Schaafsma and Baute are part of a 25-member team that is examining neonicotinoid seed treatment concerns.
Along with the yield comparisons, they are measuring the level of neonicotinoids on vegetation around fields, on foraging bees and other insects, and in field soil.
Schaafsma said he was surprised to find the insecticides in soil outside of fields where they had been applied. However, he sees more benefit to the seed treatments than Krupke.
Early crop growth appears to be positively affected, he said, although that doesn’t necessarily translate into higher yields.
The insecticides are also convenient and cost effective. Low rates cost about $4 per acre.
Schaafsma said it would be a challenge to co-ordinate the treatment of seeds if measures to reduce their use are introduced. Treatment often occurs months before the seed is planted, when growers are unlikely to know their level of risk for insect damage.