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Can Sunflowers Ignore Weeds?

Thanks to research being conducted by David Horvath at USDA-ARS in Fargo, ND, sunflowers might one day be able to “ignore” weeds.


Imagine sunflower hybrids that could thrive in a field full of weeds or other crop plants. Sunflowers that would literally “ignore” the weeds and other crops that surround them and grow to their full potential, without the need for herbicides.

Thanks to research being conducted by David Horvath at USDA-ARS in Fargo, ND, the above scenario might one day be possible.

Horvath is examining genetic data from Nuseed sunflower hybrids to see how they respond to weeds and high-density planting situations. He says by the beginning of 2024, a comprehensive paper will be published on which genes affect how sunflowers respond to competition in the field.

Theoretically, breeders can then create new varieties where these genes are turned on or off so the plants can better thrive among weeds or in double cropping situations.

Even though the research isn’t quite ready to be revealed yet, Horvath and his team have gleaned some key insights into how sunflower responds to weeds and competition from other crops — namely, that weeds do not reduce crop yield in the way we have traditionally thought they do.

“Everyone’s always thought the reason why you get reduced yields is because the weeds — and in some cases other sunflowers — are sucking up all the nutrients out of the ground and depriving the sunflower of resources. But that isn’t why weeds are reducing yield,” Horvath says.

“Many growers are familiar with the critical period for weed control which takes place very early in the season, when the plants are tiny. If weeds aren’t controlled during that time period, you lose yield, even if you remove the weeds afterwards.”

The thing is, this critical period for weed control is early in the growing season. The weeds are smaller than the sunflower, for the most part, he notes.

“The plants are far apart, there’s usually plenty of moisture and nutrients still in the ground, right? But that’s the time period when the weeds are causing the sunflowers
to reduce their yield.”

What Horvath and his team think is happening is that the sunflower, at that early stage in the season, detects the weeds, then changes its physiology from a high growth to a defense response, where it conserves resources and makes sure it expends just enough energy to grow enough seeds to ensure the next generation is planted.

“If we can figure out how that sunflower detects those weeds and responds to them at a genetic level, then we can block that response. The result is the sunflower can pretty much ignore the weeds, at least in most well-managed fields where growers have done a good job of fertilizing.”

He goes on to say that if the sunflowers are not panicking because they detect weeds, they will simply continue to grow to use the available nutrients to create as many seeds as possible.

“There are plenty of nutrients by the end of the season for them to get a pretty decent yield out of, even with weeds present or in high-density plant situations.”

He adds that the findings of the research may be able to help with double cropping and cover cropping as well.

“If you could create plants that essentially ignore other crops around them, you can throw in some camelina or another earlyseason crop that you can grow right along with the sunflower. As long as there’s enough nutrients in the soil for the sunflower to get good yield at the end, you can do that and get two crops off the same field. Who doesn’t like that idea?” Horvath adds.