While low-input, conventional-variety cotton production systems still boast some popularity in parts of Alabama, this might be the year growers should focus more on maximum yield potential, says Ron Smith, Auburn University Extension entomologist.
“For 2011, this may not be the season to try to cut input costs,” says Smith. “I would focus instead on trying to maximize yields this year because of the price of cotton.”
Researchers have been growing conventional cotton in Prattville, Headland, Fairhope and Shorter, Ala., says Smith. “We’ve calculated the seed costs, the technology costs, the weed control costs, the foliar insecticide costs, and the yield. We have a wide range of varieties, including Roundup Ready alone, insect resistance alone, and some pretty good conventional varieties,” says Smith.
Weed control costs generally are going to be a little more if you don’t have Roundup Ready cotton, he says. The foliar insect costs last year — because there were few caterpillar pests — were all the same.
“We sprayed twice for stink bugs over all of these varieties, but did nothing for worms. If you have worm pressure, that’s when you can get into some big differences. Our cost for pounds of seed cotton ranged from about 2.3 cents per pound to up to about 4 cents. It was pretty economical last year to do all of those things,” says Smith.
The bottom line with planting conventional varieties, based on research results from the past several years, is that economics will vary greatly depending on the weather, the severity of the insect pressure — particularly caterpillar pests — and the location, he says.
“We get more worm pressure in the southern part of the state than in the central part of the state, and even less in the northern part of the state. (To see an earlier story on how Ron Smith would control insects in conventional cotton, please visit http://southeastfarmpress.com/cotton/conventional-cotton-changes-insect-control. To see why some growers have been planting conventional cotton, please visit http://southeastfarmpress.com/cotton/alabama-growers-stick-conventional-cotton.)
Requires a lot of expertise
If you’re going to grow conventional cotton, says Smith, it’ll require a lot of expertise, a lot of monitoring, and selecting the appropriate chemistry for the specific worm that is in the field at that time.
“You’ll need to have a top-notch scout, and if it was me, I’d be losing sleep at night in fear that I’d be getting behind on some of these. You have a high risk with conventional cotton when you get into some of these caterpillar pests like tobacco budworms and fall armyworms,” he says.
Looking at the evolution of Bt cotton and new varieties that are on the horizon, Smith says it’s important to add new genes to provide improved effectiveness across the various caterpillar species.
“With the single gene alone, we’d have escapes in the bollworm species and in the fall armyworms. The big thing is to manage resistance and preserve the technology. Have you ever considered the significance if resistance had occurred to the Bt gene when we had only the single Bt gene?
“I know we all loved 555, but we were living on the edge with that variety. If they had ever documented resistance in 555 or in Bollgard, beginning immediately there would have been no more Bt cotton sold in the county where resistance was found. There was a plan worked out with EPA, and it would have been a disaster if we had seen resistance before we got the stacked genes.”
Looking at other insect-related issues facing cotton producers, Smith says many growers have moved to seed treatments for controlling early season pests.
“And even though they may not be as consistent as Temik, we can make an early season foliar over-spray and get adequate early season thrips control.”
In the future, he says, the bigger impact of losing Temik might be for its control of spider mites. “Back in the 1940s through 1960s, spider mites completely defoliated fields of cotton. In 1970, the problem went away, and it pretty much had been gone away until recent years. In some parts of the Cotton Belt, spider mites are flaring up almost every year. Temik was the best suppression tool we ever had for spider mites. That will be a big long-term impact of losing Temik. We’ll have some new materials for spider mites, but they’ll run you about $18 to $28 per application, and you’ll be buying yourself only about 10 days of protection.”
Researchers, says Smith, also are looking at a faster sample system than is currently available for stink bugs. “We have a good system but it’s not fast. We’re trying to come up with a more rapid survey technique. Our current method is very good. We pull from 25 to 50 or more quarter-diameter or larger bolls per field. We crush them and we examine them for internal injury. That’s either boll rot, stained lint or the carpel wall warts that you get, which later deteriorate either one lock or the entire boll.
Accurate system, but time consuming
“It’s an accurate system, but it’s time-consuming, and what most of the field people are doing is cutting down their sample size. I’ve got good friends who sample 10 bolls per field because they don’t want to stand there and crush bolls all day.”
Researchers have been working with some fields in Headland to try and correlate the external damage, which is quick and easy to see, with what’s on the inside without having to burst the bolls, says Smith.
“If we can do that, we can take a much better sample size and get a more accurate count on stink bugs. There are still people just looking for adult stink bugs in the field, but that won’t work. You’ll have an economic level before you ever find many stink bugs. If we use drop cloths, like we do with soybeans, our sample size is too small.”
Last year, researchers collected quarter-diameter bolls from replicated strips with different treatments and different chemistries. “Based on what we collected, as the number of external injuries increase, we get a corresponding increase of internal damage, particularly if they haven’t been controlled well. As the season progresses, particularly in untreated cotton or in cotton treated with less effective chemicals, you’ve got more bolls with a higher number of external feeding and corresponding internal damage.
“And in the more effective treatments, like Bidrin, you have less damage as you move through the season. Based on this trial, we can conclude that stink bugs produce varying levels of boll feeding and corresponding internal damage based on the effectiveness of the insecticide you use. In this test last year, the majority was the brown species.”
Other factors that have an impact on the severity of stink bug pressure include the time of the season, whether or not the field has been previously treated, the length of time since the previous treatment — nothing will hold much longer than about 10 days, the number of stink bug applications — sometimes, it takes a second application to really suppress them, the effectiveness of the treatment, and the species of stink bug you’re dealing with.
There are a few new damaging insects that producers need to aware of, says Smith. “The kudzu bug came in from China, has spread from Georgia to the Carolinas, and now we’ve found it in two northeastern counties in Alabama. In China, it fed only on legumes. In Georgia, where they were left uncontrolled, they reduced soybean yields by about 20 percent. They’re easy to kill with most of the pyrethroids.
“The brown mormorated stink bug is very damaging, and we’ll have to throw it into the mix of damaging stink bugs. We also have the red-banded stink bug. They are devastating feeders of soybeans, and we found them for the first time last year on the Gulf Coast.”