One of the few positive things that can be said about the 2006 cotton year in Alabama is that insect numbers were low to non-existent in most of the state’s fields and across most species of insects, says Ron Smith, Auburn University Extension entomologist.
“Despite the low insect pressure, I think we have learned a few things this year,” says Smith. “We conduct thrips tests in Prattville every year, and it was an exceptional year for thrips because pressure was so heavy during a certain window. It appeared that when the cotton was most susceptible, the thrips moved from the wild host plants and into the field. No matter what we used as a treatment, it didn’t look good. The best thrips treatment we had this year was where we sprayed three times with Orthene in a timely manner.”
If cotton is at this susceptible stage when the primary migration of thrips from wild host plants occurs, then nothing will work very well, he says.
“They’ve got to feed a little bit before they can be killed. If you have a lot of thrips feeding a little bit, then you get some cosmetic damage in all of the better treatments, and that’s what happened this year. My point is, there’s a window during which cotton is more susceptible to thrips. And at that time, with a mass migration, you’ll probably need some supplemental treatments in some years,” says Smith.
Plant bugs were almost non-existent in Alabama cotton this year, perhaps with the exception of the Tennessee Valley, he says. Aphids lasted three weeks to a month longer than normal, he adds.
“The naturally occurring fungus that usually takes out aphids needs humidity and moisture to spread and to show itself. That did not happen this year. Instead of aphids crashing in the first 10 days of July, they crashed the last 10 days of July. We made a lot more foliar sprays for aphids this year than we normally make. We probably made more foliar sprays for aphids this year than for any other insect pest. We now have good chemistry, and most folks were pleased with what they saw,” says Smith.
The normal time to see a heavy flight of bollworms, he says, is about July 20. But that was at the peak of Alabama’s drought this year, and the flight never occurred.
“But you didn’t have to go too far to see the opposite. In southwest Georgia, including Dawson, Albany and Camilla, growers saw heavy pressure during that window. It was at a level to where the Bollgard cotton didn’t hold, and they had to make multiple oversprays to take out the worms.
“Last year, the pyrethroid chemistry didn’t work in that area, and they had up to 10-percent boll damage. Bollworms were escaping Bt cotton. That didn’t happen as bad this year. The resistance level may have dropped back some this year, but it’s a problem just waiting to happen on a much larger scale. That is, the effectiveness of pyrethroids on bollworms.”
Stinkbugs, says Smith, also were difficult to find in Alabama cotton this year. “Stinkbugs have become the No. 1 pest of cotton in this part of the country. But we didn’t know that heat and drought would take its toll on the pest. If that didn’t do it, then I’m not sure what did. We learned one thing about stinkbugs this year — they’re not the same every year. If you don’t have a scout or a consultant, the trend has been to spray for stinkbugs the third, fifth and seventh week of bloom. This year, you would have wasted more money than a scout or a consultant would have cost you by spraying on that schedule. The sprays would have been of little benefit.”