“It’s taller, the leaves are wider and the stalks are bigger around.”

Jerry Fraim, Caneyville, KY, is describing silage corn that had been treated with a plant growth regulator early in the growing season.

At the crop’s five-leaf stage, he applied RyzUp SmartGrass, a gibberellic-acid product registered by the Environmental Protection Agency for use on silage corn earlier this year. Gibberellic acid is a naturally occurring plant stimulant that promotes early plant growth.

Fraim supplements pasture with corn silage for his 400 beef cows and backgrounded calves. He saw a yield response when he tried RyzUp SmartGrass in test strips for Valent U.S.A. Corp. in 2011, so he used it on most of his 180 corn acres this year.

“You’ll gain between a ton and a half and three tons,” says Fraim, whose normal corn silage yield is 20-22 tons/acre. “We’re real dry down here this year, but even last year we noticed that, where the corn had sufficient moisture, it made more difference than where it didn’t. It will increase yield, whether it’s a very poor yield or a very good yield.”

He tankmixed the growth regulator with a postemergent herbicide on a few of last year’s test strips, but applied it alone in 2012. He applied 0.3 oz/acre, the recommended rate, and his expenses totaled $7/acre for the product plus the spraying cost.

“Two weeks later, I could tell the difference in the color,” he says. “I thought the plants looked healthier, and during our drought this year the corn didn’t twist as bad.”

RyzUp SmartGrass is also registered for use on cool-season grasses and small grains, and university research has shown positive yield responses. Trials on silage corn were established at universities in Illinois, Indiana, Iowa, Missouri and Ohio this year, but some were lost due to drought, says Jim Wargo, a Valent commercial development specialist.

When the growth regulator is applied between corn’s second- and sixth-leaf stages, a visual response is noticeable within a week to 10 days, and lasts about a month, says Wargo.

“Eventually the corn that isn’t treated will catch up,” he says. “It’s not going to make the plants a foot taller at tasselling. We’re trying to get that plant off to a healthier start to influence those early physiological processes that are so important for determining yield.”

It isn’t a substitute for good fertility or sufficient moisture, he adds. “As long as those things aren’t limiting, you could expect a rapid and significant response.”

Sold in 3-oz bottles, the product can be tankmixed with herbicide or fertilizer, and is most effective when applied on days too cool for optimal plant growth, says Wargo. On cool-season forages it should be applied in the 40-60°F range, but corn has a wider application window.

“We’ve even put it on corn when the temperatures are in the 70s and even 80s and we’ve still seen a response.”

He says gibberellic acid enhances cell division and elongation in plants and has been used on a wide variety of crops since the 1950s.

“The effects are grounded in science and physiology,” he says. “I think it’s important for someone to know that we’re not just coming up with phoo-phoo dust in a bottle. We’re really looking at this as something that could be part of farmers’ standard practices in the years to come, just like they would fertilize or use a herbicide.”