PGRs: Same Song, Different Verse
August 20, 2009 Application timing of plant growth regulators is always critical. Apply PGRs too early and take the chance of losing growth potential that results in losses in both yield and quality. Apply PGRs too late and take the chance of delaying a crop and leaving it in the field if weather conditions turn nasty.
This year, PGR application timing will be even more critical. Across the Cotton Belt are fields that were planted early and then replanted after heavy rain, cool weather and even hail. There are fields planted into dry dirt that emerged slowly and with less vigor. You name it, and there was almost always an adverse condition to affect a field.
“We have some weather come through and we’ve had to replant some cotton,” said Dr. Randy Boman, Texas AgriLife Extension cotton agronomist in Lubbock in early June. “We’re still sitting on the bubble for about a million acres of dryland. That’s going to run right up against the wall in terms of whether we get rainfall, and if we do, we could be stuck with a fairly late crop.”
Boman said a field in a drip-irrigation trial near Lubbock was hit with two hail storms. The field survived the first, but not the second. It was replanted and will mature late.
“A lot of times late cotton under irrigation tends to be more growthy. What I tell guys is to be sure they don’t over fertilize with nitrogen and compound the problem, because that can lead to excessive vegetative growth. So they need to be more on point for PGR use ― especially on the picker varieties.
“In general, the FiberMax varieties doesn’t tend to get real big for us out here ― I’m not saying they can’t ― but in general we don’t necessarily have to apply a lot of PGR. It’s really more field by field, and variety by variety.”
The Texas AgriLife Extension Service has been publishing a harvest-aid guide since 1997 and it’s been update yearly. The 14-page 2008 Cotton Harvest Aid Guide is available on the internet at lubbock.tamu.edu (Don’t use “www”).
“We’ve done studies scattering harvest dates from September through January and February,” said Boman. “What we found is that the earlier you get the cotton out, the better off you’re going to be – not only from the yield standpoint, but also from the quality standpoint.
“We did the test with one of the older, storm-proof stripper varieties ― Paymaster 2326 ― and in one of the three years we saw a pretty significant yield decrease from later harvesting, and that was associated with an ice storm.”
So Boman recommends that if growers plant less storm-proof varieties, they should plan ahead for a good harvest-aid program to make an earlier harvest more likely, and not have to sit through, or even survive, adverse weather conditions.
Peachtree PGRs
In Georgia, the crop is behind almost across the board, said Dr. Jared Whitaker, an agronomist with the University of Georgia Extension Service.
“We have cotton behind wheat that is late ― that’s typical,” he said. “We’ve had some areas that were wet, and some areas that were real wet. They are going to be late. In this situation, we don’t have a lot of time to delay harvest.”
One unique management challenge in Georgia is the state’s love affair with Delta and Pine Land’s DP 555 BG/RR, with an 85.85% market share. 555 tends to be a growthy, vigorous variety with a dense canopy. It has its own set of PGR requirements.
So the dilemma in Georgia is: The crop is late, the 555 is growing like crazy and the tropical storm and hurricane season is upon us. What do you do? Slow it down in hopes of picking ahead of the rains, or turn it loose so that it reaches full yield potential?
In general for all varieties in Georgia, Whitaker says one thing to avoid is putting out a PGR too early.
“Don’t put on too much too early and stunt it,” he explained. “Make sure you get your fruiting positions set and get the boll load early. PGR applications are sort of like a magic trick, but I would be less aggressive and let it get up and growing.”
Second Generation
The first plant growth regulator to make its way to the cotton market was BASF’s mepiquat chloride product Pix. Stance from Bayer and BASF’s Pentia are both mepiquat-chloride based, but could be considered a second generation because they both contain a second compound.
Stance also contains cyclanilide, an inhibitor of cell elongation and growth. With Pentia, BASF removed the chlorine ion from mepiquat chloride and replaced it with five borate molecules.
“We’ve been working with Stance since it was a numbered compound. As far as providing growth control, it’s excellent,” Boman said. “It simplifies the process – a grower might want to apply 2 or 3 ounces per acre, depending on what the specific field situation is. If they’ve got more growth potential because of either rainfall or high irrigation capacity, they will probably want to go with a little higher rate.”
Dr. Fred Moore, BASF’s Technical Service Representative for Texas, Oklahoma and New Mexico, said timing is everything, whether a crop is late or not.
“The timing at pinhead square is key to control growth and get the most out of it you can,” he explained. “Then be watchful as internode length progresses from then on.”
The boron ions in Pentia help the plant absorb the PGR component faster, drastically increasing rainfastness.
“What you’re looking at is 2 hours with Pentia versus 8 hours with mepiquat chloride,” Moore said. “If you include a non-ionic surfactant, it’s one hour. The boron ions are doing that.”
The labeled rates for Pentia range from 4 ounces to 24 ounces. “But what we’ve seen in the Southwest, 16 ounces is the highest rate you really need at any one time,” Moore said.
“Each field should be looked at on an individual basis. It’s hard to make a generalized recommendation on multiple fields,” he continued. “It’s field by field.”
Add captions:
On the right is cotton treated with Stance. On the left is an untreated check.
A late-maturing crop is sometimes at the mercy of adverse weather. Source: Louisiana State University Extension Service
Dr. Randy Boman
Dr. Jared Whitaker
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