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In Arkansas Green soybeans prolonging harvest

Since mid-September, Arkansas soybeans have behaved oddly, refusing to fully mature and pushing harvest later into the fall. That has many wondering if wheat will be planted in an optimum window.

Beans in pods are ready to harvest anywhere from 15 to 18 percent moisture. However, the plants still have green leaves and stems. If farmers try to harvest them, the moisture level will likely increase due to the green material.

“Farmers are in a dilemma,” says Jeremy Ross, Arkansas Extension soybean specialist. “What to do? Well, we could wait until the leaves finally drop off — and there should be a frost in the next month. But going that route will put growers way behind, especially if they're looking to plant wheat behind the beans.

“The other option is to fly on Gramoxone or sodium chlorate to dry the crop down. If you do that, make sure to read the label, though. I believe there's a seven-day harvest interval on paraquat.”

In Prairie County in central Arkansas, “the biggest issue currently is our soybeans don't want to shed leaves,” says Hank Chaney, Extension agent. “We're in mid-October and still trying to get the crop out. I don't know that it's a green bean syndrome problem as much as we've had second growth in the beans. Having 80 to 90 degree weather in October has to be spinning the crop's head.”

Chaney's is the consensus view, says Rick Cartwright, Arkansas Extension plant pathologist. “I've spoken with a number of consultants and specialists about the soybean situation. Most are convinced this is a response to the weather we saw from mid-July on. It turned so hot, so dry, so fast that it had to have an effect.”

Even though many of these fields were irrigated, daytime temperatures never dropped below 94 degrees, points out Ross. And for a 10-day stretch in mid-August, it was over 100 degrees.

The beans, at that time, were in sensitive stages. And to top it off, many fields were water-stressed, even though growers tried to keep up with irrigations. The beans, in those conditions, appear to have been confused.

“They were unsure whether to keep growing or go ahead and mature. What ended up happening is the top of the plants went one way and the bottoms went the other. We've ended up with green stems and mature pods with the upper canopy still hanging on.”

There has been speculation that disease could be the cause of the late-season soybean problems.

“I've spoken with several people claiming this is caused by cercospora leaf blight,” says Cartwright. “There are a couple of problems with that diagnosis.

“First, cercospora leaf blight has easily identifiable symptoms — it'll turn the tops of leaves reddish-bronze and leathery. In many of the green soybeans, we aren't seeing that.

“Second, cercospora leaf blight, once it's going and blowing, causes leaves to fall off. That's been my experience anyway. But these fields are keeping their leaves, not losing them.”

Another possibility involves aggressive use of fungicides this season. In years past, certain fungicides in certain conditions have caused leaf retention.

“Some call it the greening effect,” says Cartwright. “I've seen that happen with fungicides before.”

But this situation seems different. Fields treated with fungicides are showing the same symptoms as neighboring, untreated fields.

“Those fields have the same planting date and basic management, except for the fungicides, and they've all got leaves hanging on. There doesn't seem to be a consistent pattern to support the claims that fungicides are the cause.”

Asian soybean rust continues a slow crawl through the Delta. Almost every soybean-growing county in Arkansas has had a positive confirmation for ASR.

“The good thing is they came in late enough that the majority of the crop was past the point where we recommend spraying at R-6,” says Ross. “The beans we were worried about were the late-planted and double-cropped soybeans. But that was only around 10 to 15 percent of the Arkansas acreage.”

As mentioned earlier, many Arkansas fields were sprayed with a fungicide. “There were areas where farmers went ahead and sprayed to make sure they were protected. Others held off. The good thing is the conditions we've had didn't allow the rust to spread as quickly as we thought it would.”

When ASR first geared up in the state, Ross and Scott Monfort, Extension plant pathologist, “thought it would run all over the state. We thought we'd see some cases of untreated fields being defoliated in 20 days. But that wasn't the case. It progressed slowly and we got lucky.

“We have test plots in Lonoke County — and Cliff Coker (Extension plant pathologist) has some in the southwest part of the state — to get information on fungicide activity in Arkansas. A lot of the information we have is from other states or South America. We're trying to take advantage of the disease coming in so we can get Arkansas-specific rate and chemical data.”

Positive confirmations of the rust are still occurring. However, suspicious leaf samples from soybeans and kudzu have slowed down tremendously.

“ASR is present on kudzu. I just came from the lab. There were a handful of leaves being checked.

“How cold it gets this winter and how far south ASR is pushed will play a key role in how severe it'll be next year. The latest, long-term forecast is calling for a drier, warmer winter. We don't need that — we need some freezing temperatures.”

Early in the growing season, stink bug numbers were very low in the state. “We figured we'd have a light stink bug year,” says Ross. “But they kicked off in late July/early August. They've been building steadily ever since and acreage has been sprayed.”

Ross was walking fields Oct. 10, “and stink bugs were still easy to find. They're still hatching. Possibly, some of this ‘green bean’ syndrome may be a combination of August stresses and stink bug damage.”

Chaney says there have been “a lot of stink bugs in soybeans I've swept at the end of the season. There were growers who, when spraying for ASR, also put out an insecticide.

“I've got my fingers crossed that these stink bug numbers aren't the main cause of these green beans. Hopefully, it is just weather. But everyone is complaining about them.”

Reported yields from around the state have been fine, says Ross. The dryland crop is coming in at 15 bushels to 35 bushels with many irrigated yields between the mid-60s and mid-80s.

Unfortunately, no one has yet hit 100 bushels in the Race to 100 contest. “So far, the closest reported is 92 bushels. We've had a lot of yields in the 80s and high 70s. It doesn't look like we'll have anyone cut 100 bushels this year. If it was going to happen, it probably would've come from the early-planted crop. The beans being harvested now were probably planted too late to get maximum yield. I hope I'm wrong, but I'll be surprised if we get a winner in the next couple of weeks.”

Earlier, Ross thought several fields would go over 100 bushels. Then August arrived and numerous calls started coming in from growers, consultants and county agents saying, “‘Man, these good beans are dropping pods, dropping blooms.’ When I heard that, I thought, ‘Well, August is going to take out some of that early yield advantage.’ And that's exactly what happened.”

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