Pests Attack When Cotton is Most Vulnerable
March 12, 2009 Fortunately, cotton diseases ― Pythium, Fusarium, Rhizoctonia and Phytophthora ― are not annual problems and are mostly weather related.
But it still pays to be proactive.
“On-seed treatments are popular in Texas; 100% of our commercially available varieties come with some sort,” says Dr. Jason Woodard, a Texas Extension plant pathologist. “Typically we see improved stands, regardless of the year, but we don’t always get a yield increase. In 2007 when we had cool, wet conditions, in artificially inoculated studies, we did see (on-seed) treatments provide superior yields. That indicates to me that if producers have a farm with a history of high seedling disease pressure and it’s cool and wet, you may see a yield response.”
Woodard adds that commercially available on-seed treatments have a high degree of effectiveness. “Overall, the commercial standards are very good,” he said.
Growers also have the convenience of on-seed treatments of insecticides and nematicides.
Cruiser, an insecticide, and Dynasty, a fungicide, are products offered by Syngenta as on-seed treatments. Those two are used in Avicta Complete Cotton with the nematicide Avicta added.
Bayer CropScience has two on-seed treatments: Aeris and Trilex Advanced. They can be used as stand-alone products or combined. Aeris is an insecticide; Trilex Advanced is a fungicide. Temik from Bayer continues to be one of the most recommended granular insecticide/nematicides.
Recently BASF introduced Coronet fungicide, and Dow AgroSciences has the nematicide fumigant Telone.
Don’t Let ‘Em Bite Young Cotton
Although seedling diseases are not a yearly problem and nematode populations can vary from field to field, thrips are a problem every year.
According to a Cotton Foundation-funded study by Mississippi State’s Entomology and Plant Pathology Department in 2007 ― the latest data available ― thrips cost U.S. growers 145,040 bales. This puts thrips at a dubious third place behind the budworm/bollworm complex and plant bugs as the most economically damaging pests.
“Thrips are a very predictable pest in Georgia,” says Georgia Extension entomologist Dr. Phillip Roberts. “Most of our growers are going to use some type of preventive treatment at planting. When we look at options, we have Temik or the insecticide seed treatments.”
Roberts says there are two main considerations for early season thrips control: time of planting and cool temperatures. “Anything planted in April and the first part of May typically has our highest thrips pressure,” he explains. “Slow plant growth compounds the problems with thrips.
“If a grower is planting early and is expecting heavy thrips pressure, he needs to use something with residual activity. Understand the situation you are in and select an appropriate treatment. Temik is usually going to give us four-plus weeks of residual control, but it’s rate dependent,” continues Roberts.
Roberts says on-seed treatments usually give up to three weeks of control and in some instances that may not be long enough. “If that’s the case, you may need a foliar spray to supplement the seed treatment,” he explains. “But again, it’s knowing what you’ve got and how to deal with it.”
Roberts adds that you’ll generally see fewer thrips pressure in reduced tillage fields, but why remains a mystery. “A lot of people think it would be just the opposite,” he says. “But the difference is night and day.”
Resistant Palmer Amaranth:The Devil’s in the Details
As bad as glyphosate-resistant marestail is, it pales in comparison to resistant Palmer amaranth.
Dr. Chris Main, University of Tennessee Extension cotton specialist, says glyphosate will continue to be the base weed-control product for the foreseeable future: “We are not talking about getting away from glyphosate. But we need to ask ourselves what we can do to partner glyphosate with other materials to get better control of our glyphosate-resistant weeds we are battling.”
In a related story in the February issue of Cotton Grower, Mississippi Extension cotton specialist Dr. Darrin Dodds said, “Think back to 1995 or so. What were you doing for weed control? You went out in the field, identified the weed species and how big they were. Then you selected the chemistries knowing that they were going to take out certain weeds and leave certain weeds. That’s why we started coming in with more than one chemistry.”
What they are both saying is that it’s time to go back to tank mixes with a residual herbicides added.
“Even after a good burndown, we need to come back with a preemergence material that we have not used in a while, like Cotoran or Caparol,” Main continues. “I’m not suggesting that you put out two quarts of either and yellow up the cotton. What we want to do is put out 1½ to 2 pints of those products to buy four weeks of residual control.”
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