Planting high quality cotton seed and keeping young plants healthy early in the growing season is one of the keys to growing cotton in Virginia, says long-time Virginia Tech Plant Pathologist Pat Phipps.
After last year’s problems with a late tropical storm and hurricane, Virginia growers are looking for ways to get their crop up early in the 2012 season, and, hopefully, make up for some of the lost production from the storms in 2011.
At a recent field day at the Tidewater Agricultural Research and Extension Center in Suffolk, Va., Phipps showed growers the results of several different seed treatments used to protect the crop from early season disease damage.
An often asked question among farmers growing cotton in the northern ranges of production is, “Do I need more protection against early season diseases than the standard seed treatments provide.”
In the Virginia Tech tests, Phipps compared the standard cotton seed treatments — Avicta Complete Cotton from Syngenta and Aeris from Bayer to untreated cotton seed. As expected, there was a significant difference in stand and subsequently a significant difference in yield between untreated and treated seed.
Avicta Complete Cotton is a combination of three Syngenta products: Avicta, a seed treatment nematicide; Cruiser, a seed treatment insecticide; and Dynasty, a seed-delivered fungicide.
AerisSeed Treatment System is a cotton seed applied nematicide/insecticide. It combines the broad spectrum activity of chloronicotinyl and carbamate chemistry to provide protection from early season insects and nematodes.
“Most of the cotton we plant is with seed treated with one or the other of these seed treatments. From these tests, it’s clear these materials work. The question is do they work well enough,” Phipps says.
Phipps took seed from a high vigor batch of seed and treated part of them with a warm water heat treatment to reduce vigor. The tests comparing different seed treatments also compared these treatments in high and low vigor seed, he explains.
He points out some difference in flowering in the low vigor seed, but not in the high vigor seed. “Growers should check seed for cool germ and that will tell them about vigor of cotton seed,” Phipps says.
In Virginia, growers should plant seed with at least a 70 percent cool germ and most growers in the state are planting seed with at least an 80 cool germ, he adda.
In cotton there are two common germination tests, standard germination and cool germination. Standard germination results are reported on the seed tag. Standard germination tests are conducted at 86 degrees F for 16 hours per day and 68 degrees F for 8 hours per day.
Ask for cool germ numbers
Cool germination tests, often referred to as “cool germ” typically are not reported on the seed tag. The seed companies run this test on all seed and the dealer or distributor usually has this information. If not, the value can be obtained by calling the seed company with the lot number of the seed.
In tests with seed treated with Avicta or Aeris, the veteran plant pathologist added two different over-coat fungicide treatments. Neither of these materials provided any improvement in stand or yield, when compared to the standard seed treatments.
Likewise, in furrow treatments of Quadris and Ridomill Gold added to the base treatment didn’t provide any significant improvement over standard seed treatments.
Cotton growers were without an adequate supply of Temik for the 2011 crop and the long-used product will be even more difficult to find for the 2012 season. A generic Temik, MeyMik, appears to have cleared EPA scrutiny, but it will not be available for early season use on cotton for the 2012 season.
Based on this shortage, Phipp’s says growers have some options for protection against early season cotton nematodes and diseases.
Aeris, Avicta and Votivo —a biological seed treatment — are available to growers as seed treatments. Historically, used as a stand-alone replacement for Temik, the seed treatments have not supplied added protection against both early season insect damage and insect-vectored diseases and nematodes.
Counter, widely used for nematode management in corn, is an option for cotton. Larvin, which has the same active ingredient as Aeris applied in-furrow, is another option for nematode management.
Abomectin, the active ingredient in Avicta is also being used as an in-furrow treatment on cotton.
Both Avicta and Aeris provide very low amounts of the active ingredient in the seed. Using the active ingredient in an in-furrow treatment is a way to get more active ingredient used in either seed treatment to the plant, Phipps explains.
“We didn’t expect much thrips control from either of these materials, because neither has shown much activity in the past. But, we needed to look at these materials to try and find something comparable to Temik that will provide nematicidal activity, which these products provide, plus some activity on thrips.
Phipps says neither in-furrow treatment, used in combination with seed treatments were as good as Temik. Counter provided some thrips control, but flower counts were lower with this product.
“We’re not sure why flower counts were lower with Counter. We hope it was just a one-year fluctuation, but it’s something we will have to take a close look at for the 2012 growing season on cotton,” Phipps says.
Perhaps the best management strategy for both nematodes and thrips comes from using nematode resistant varieties and some combination of in-furrow treatments and standard seed treatments for cotton.
Two varieties, Stoneville 5458 and Phytogen 367, both provided significantly higher yields in grower trials in 2011. These fields have high populations of Southern root-knot nematodes and these two varieties had the highest yield, regardless of fungicide/nematicide treatment, Phipps says.
“In scoring the roots, plants from either of these two varieties had significantly less root gauling — not enough to hurt the plants. This is another way to manage nematodes, and using these resistant varieties will likely play a big part in replacing Temik,” Phipps concludes.
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