What is in this article?:
- It's a good year to maximize cotton yield potential
- Requires a lot of expertise
- Accurate system, but time consuming
• This may not be the season to try to cut cotton input costs
• Weed control costs generally are going to be a little more if you don’t have Roundup Ready cotton.
• 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.
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.”