How important is Roundup (glyphosate) for New York farmers?
Historically, glyphosate is the number one herbicide folks are using in New York. One recent survey showed that 86% of soybean growers in the state still just use one shot of glyphosate for weed control. A lot of farmers are seeing these resistant species for the first time, which is really threatening because the majority of folks are still using glyphosate, nothing else.
How damaging are these herbicide-resistant weeds?
Crop failures can go up to 80-90% if the conditions are just right for these weeds. We have seen some fields in New York infested with waterhemp where growers were not able to harvest their beans at all; it was just waterhemp. Last year, I saw fields like this in Seneca and in Tompkins counties. Waterhemp, Palmer amaranth and Italian ryegrass are invasive species, meaning that they have unique biology and they can grow very rapidly and very aggressively. For example, Palmer can grow up to an inch per day, if conditions are right. They can grow more than 6 feet high in some cases. They also produce a lot of seed; a single female plant of Palmer amaranth can produce more than half a million seeds. Compared to soybeans, they are more aggressive, and they compete with crops for nutrients, water, space and light. And it’s not only yield reduction. If we do not control these weeds, at the time of crop harvest, it can interfere with the harvesting – if weeds are 5-6 feet tall, hard wood, they can sometimes break the combine. They also affect grain quality: If your harvest is contaminated with these seeds, when you take your harvest to market, they dock it because of the presence of the weed seeds.
What can farmers do?
These species need a more holistic management approach. For many years, farmers could spray glyphosate once and forget about it, but we can’t do that anymore. We are looking at a host of options, including alternative herbicides, timing of herbicide application, and additional management and cultural options.
- Farmers should start looking at using early, pre-plant-emergence herbicides. This advice was changed in the Midwest years ago. It hasn’t changed in New York because glyphosate was doing the job, but it should change.
- Diversifying crop rotation is a fundamental strategy to break the pest cycle. Cover crops such as cereal rye or triticale can be integrated in corn and soybean rotations to compete against weeds. Italian ryegrass is sometimes used as a cover crop, because it grows well in cool, wet conditions, but this species can turn into a weed problem, especially now that we have documented populations with glyphosate resistance.
- In addition to cover crops, integration of forage crops such as alfalfa in corn-soybean rotations should be considered to suppress weeds and deplete the seedbank of glyphosate-resistant biotypes.
- Controlling weed seed during crop harvest, also called Harvest Weed Seed Control (HWSC). There’s a unique mechanical weed control method that’s been tested in Australia: When we harvest our soybean, this specialized unit called a “seed impact mill” can be attached to a high-powered combine. While the soybean harvest goes one way, the weeds and plant chaff are directed into this mill, which pulverizes the weed seeds and makes their seed unviable. The seed impact mill costs $75,000-$90,000 and it needs a specific, high-powered combine, so this would not be viable for every farm.
- We’re always looking out for novel mechanical approaches to control weeds, such as use of inter-row mowing or late-season electrocution of weeds.
The bottom line is that there is no silver bullet anymore. Management of these herbicide-resistant weeds will require an integrated approach and some novel techniques. We are currently investigating various alternative tools to create local data to help educate producers about what they can do to protect their crops, which protects all of our food supplies.
Krisy Gashler is a writer for the College of Agriculture and Life Sciences.
