Researchers explain the science behind coated seeds
The trend of increasing seed treatments means farmers will have fewer products to apply at the planter.
Treated seeds epitomize the old adage that good things come in small packages. Applying a layer of chemicals and biologicals on corn, soybean and other row-crop seeds shields them from diseases and pests in the early stage of growth and pushes yields higher.
"The fungicide treatment is kind of cheap insurance," says Mike Cerny, who farms near Walworth, Wis. That’s because the treatment protects newly emerged soybeans in soils that are wet and tight.
Like a package, while wrapping options are virtually limitless, the space in which researchers can work is finite, experts say. As a result, farmers can expect seeds to be wrapped in new treatment mixes that offer an increased spectrum of activity. Treatments will be applied more precisely and with smaller chemical doses.
"The trend is to continue to have fewer products that the farmer has to apply at the planter," says Mark Miller, U.S. seed treatment application lead for Monsanto Company.
To understand where treatment mixes are headed in the future, it’s important to know a little bit about seed biology, treatment activity and environmental stewardship.
First, seed coats can only handle so many treatments.
"There is a limit of 8 oz. per cwt. of the total mix (seed treatment, water, etc.) that can be on soybeans since the seed coat of the soybean is less absorbent than other seeds," explains
Emmanuel Byamukama, South Dakota State University Extension plant pathologist. "Corn is similar to soybeans. In wheat, since it is a little more absorbent, it can take 10 oz. per cwt. to
12 oz. per cwt. total mix without the seed becoming slimy and the seed treatment not sticking
to the seed."
Protection threshold. While technology exists to apply treatments to a seed in layers, says Miller, most Monsanto treatments are applied after being mixed together. Corn is packaged with three fungicides, an insecticide that’s strength is selected by the purchasing grower and polymers that bind the treatment to the seed. Each contributes to what he calls the "total load" that a seed can support. Soybeans get three fungicides—different from those used on corn—and producers can choose to add an insecticide and a nematicide.
Seed retailers can manage active ingredients in treatments down to the milligram per seed using a touchscreen control panel, Miller says. That wasn’t possible 20 years ago.
In general, high loading seed treatments account for 0.5% to 1% of the total seed weight, says Bill Hairston, director of product development for SeedGrowth at Bayer CropScience.
Second, seed treatments are intended to operate in a short window of time. They primarily exist to withstand pests and challenging growing conditions (think wet weather this spring) so the seedling emerges from the soil.
That means active ingredients have a limited shelf life. "Usually, we look at seed treatments providing approximately 21 days of protection to the seed and seedling early in the growing season; however, some insecticide treatments can suppress insect feeding up to 45 days, depending on the pest," explains Keith O’Bryan, agronomy research manager for DuPont Pioneer.
As the seedling begins to consume water and develop, the treatment is broken down and absorbed into the root system. Some biological treatments lie dormant until that growth begins, at which point they produce spores that will help the seedling.
Additionally, seed treatments today are much more active than those used in the past, notes O’Bryan, so the chemicals are applied at a lower rate. New technology also allows for rapid drying of applied seed treatment, meaning more treatments might be added down the road.
"If there is a significant advantage, then there really are few limitations that can’t be overcome by modifying the treating equipment," Hairston says.
Treatments, particularly biologicals, are being developed to mitigate plant stress and provide protection against diseases and pests such as soybean cyst nematodes. There are products under development that will provide protection against conditions such as sudden death syndrome.
In fact, even supplementary materials such as graphite and talc might not be necessary in the future, Miller says. At Monsanto, researchers are exploring how seed treatments might be adapted to help smooth the planting process. Miller says he can’t promise that the need for those products will go away but that Monsanto is looking at the possibilities.
Environmental risks. Third, environmental concerns will continue to shape treatments. Some people think seed treatments with neonicotinoids can harm pollinators such as honeybees, says Scott Stewart, insect and pest management specialist for row crops at the University of Tennessee.
University and USDA–Agricultural Research Service scientists in the Mid-South are examining that question and others to identify risks and mitigate them. Meanwhile, variable-rate application of treatments could help farmers cater to their individual soil profile while limiting the spread of resistant soil pathogens.
"I think there are still a lot of questions about the biology and what these pesticides and fungicides are doing in the environment?" says Alison Robertson, field crops pathologist at Iowa State University. "Are we building up resistance to them, or are we changing the pathogen population such that a fungicide no longer becomes as effective as it used to be?"
A Global Industry
A recent report shows just how important seed treatments are as a business. The international market, valued at $2.43 billion in 2011, is expected to grow to $4.45 billion by 2018, according to Transparency Market Research. Insecticides accounted for 52.5% of total market revenue in 2011, followed by fungicides at 34.9%. Treatment with nonchemical biological agents is expected to grow more rapidly during that period, with nearly 10% compound annual growth between 2012 and 2018. Corn tops the list of crops, creating 34.7% of global revenues in 2011, followed by soybeans, wheat, canola and cotton. Seed treatment demand is expected to grow the most for canola.
North America led the global seed treatment market with 42.8% in 2011. Latin America took 24.2%. The report says select companies hold a majority of the market on seed treatments, with four of them accounting for 80%. Syngenta and Bayer CropScience held more than 60% of the market in 2011. Monsanto, BASF Agriculture Solutions, DuPont Pioneer, Chemtura and Nufarm Americas Inc. also sell seed treatment products.
You can e-mail Nate Birt at firstname.lastname@example.org.
- Seed Guide 2013