As everyone becomes familiar with a new herbicide, hiccups are to be expected. Loyant, used on rice field weeds, is proving no exception — especially in Delta soybeans.

“I hate that this is drawing attention, but we’re having issues with Loyant damage to soybeans,” says Tom Barber, Arkansas Extension weed specialist, during late May. “That’s the long and short of it, and we’re trying to wrap our heads around what’s going on.

“We know soybeans are very sensitive to Loyant, and it doesn’t take much drift to cause symptoms to show. When they’re hit, the young plants roll upside down. It does more to twist the petiole and stem than it does to malform the leaves.

“I don’t have a handle on how widespread the situation is — I haven’t walked any damaged fields as of today— but we’re getting calls and pictures from all over the state, mostly on beans, but we suspect some on cotton as well.”

“Adjacent”

The first couple of calls about damage to soybeans “started coming in a few weeks ago right as some applications of Loyant began in south Arkansas,” says Jarrod Hardke, Arkansas Extension rice specialist. “We became aware of a few soybeans hit after ground-rig applications. Those reports weren’t surprising straight out of the gate, because we know soybeans are very sensitive to Loyant, and the herbicide is new and everyone is just getting used to it.

“The damage was in ‘adjacent’ bean fields and the wind at spraying was ‘predominantly away.’ That’s by-the-label, but some soybeans were being hit with low-level drift.”

Since then, says Hardke, “things have progressed a bit with spraying since the central and northern half of the state’s rice fields are now getting to the point when they’re ready to flood. Well, Loyant is a pre-flood herbicide, and so we’re seeing more going out in the last week, or so.”

Loyant is a very reactive herbicide to broadleaves.

“You see symptomology fast. It isn’t a burner but an auxin, so it’s a twister and turner. Between ground rigs and aerial applications — and we don’t know all the layers of conditions, obviously, under which each application went out and how strictly the label restrictions were adhered to — this is a herbicide without room for error. You can’t spray and have wind toward adjacent soybeans, at all, and we need to be spraying at 10 gallons per acre. But one thing we do know is some of the damage was done to soybeans a half mile or farther downwind.”

Regarding the label, “one of the questions is on the word ‘adjacent,’” says Hardke. “By anyone’s definition, that would mean next door, right across the turnrow, right across the ditch. The reality is some common-sense distance must also be applied to that and a half-mile is probably a good start. Again, that isn’t on the label, but just saying ‘adjacent’ leaves a lot open to interpretation when you’re trying to make a safe application.”

Have there been any changes in application procedures?

“I know there are an increasing number of pilots refusing to put out Loyant,” says Hardke. “I don’t know if that policy is well-founded, but the rumor mill gets cranked up pretty fast. Regardless, a lot of guys are being cautious — you know, ‘I don’t have to take this risk until we know more about what’s going on.’

“On a positive note, the weed control we’ve been getting out of Loyant has been excellent. Control of barnyardgrass and broadleaf weeds has been as expected and growers have been very pleased with those results.”

Replanting?

What about replants?

“I haven’t advised anyone to replant yet. Up until this week, the fields I’ve heard about have been recovering fairly quickly,” says Barber. “Again, though, that’s up to early (the week of May 28), and who knows what the next few days hold? But I’m told the young beans are straightening back up after a few days. Long-term, we don’t know what that will mean for yield until we harvest.

“Like most herbicide injury to soybean, R1 or R2 is generally the most sensitive stage from a yield-limiting standpoint.”

With the experience of dicamba damage so fresh, the comparisons to the current situation are inevitable.

“Several have asked about the difference between Loyant and dicamba and based on our data soybeans are way more sensitive to dicamba than they are to Loyant — especially at rates as low as 1/1000X of a labeled rate. However, it doesn’t take much Loyant (1/100X) to cause symptoms in soybean,” says Barber.

There are a lot of questions yet to be answered.

“We don’t know exactly the drift rate that is affecting the beans, but based on our research we do know that yield loss is usually dependent upon the drift rate and growth stage of soybean when injured,” says Barber. “Environmental conditions following injury will determine how well the plant will recover and whether or not yield will be affected. One thing that’s for sure, though, is beans are sensitive to Loyant and some reports of symptoms are a half a mile or farther away from the application based on reports.”

Loyant, Barber reminds, “is a new herbicide and there’s always a degree of growing pains associated. But it’s hard to say much definitively when we’ve just really begun to spray in earnest over the last two weeks. The weed control reports where Loyant has been sprayed are excellent. This herbicide is desperately needed in rice and I hope that we can figure out a way to use it safely and keep it as an option in our weed control toolbox.

“It is very important that applicators follow the label when making Loyant applications. There are several reports of applicators already refusing to spray Loyant especially by air, due to the off-target issues.”