This year, in a concerted effort, Angela Thompson and colleagues set out moth traps to determine where and when the southwest corn borers were coming inside Tennessee's borders. So far, “we've been rather surprised at the numbers we're trapping,” says the Extension corn and soybean specialist. “The early generation is large.”
It may not be a harbinger of bad things to come, but producers need to know the possibility for borer problems, says Thompson. “Farmers need to keep their eyes peeled.”
“We've got traps from west Tennessee all the way into the middle part of the state,” says Russ Patrick, Extension entomologist. “Trapped numbers have been pretty consistent right across that range.”
Most Tennessee producers don't spray for the first generation. The generation Thompson and Patrick are most concerned about is the second — and the potential for that one to be heavy is picking up.
“In other states, 75 to 80 moths per trap per week may not be a large number,” says Patrick. “In Tennessee, though, that's a substantial increase over the norm. The last time we saw such moth numbers was 1998-99.”
Current trap numbers have been seen since late May. “We'd had the traps out for a month and suddenly the flush came,” says Patrick. “The numbers seem to be building more than they had in the past.
“It looks like the increased moth counts are statewide. It's definitely the case in western and middle Tennessee. I don't have traps in the east, but if precedence holds, corn borers are there, too. They were in eastern Tennessee last year.”
There are plans later in the season to make some “oversprays” in areas where it's believed the corn borers will be especially heavy. “We want to see what treatment options work best to prevent damage,” says Thompson. “If spraying isn't an option for a producer — maybe he can't get a plane in — we'll encourage him to harvest his corn as soon as it's ready. In those situations that's the proper approach. To help prevent lodging, you don't want to leave the corn out any longer than necessary.”
Overall, Tennessee's corn is doing well — especially since the first of June, says Thompson. “However, some of our corn planted after Easter has struggled. We have some fields with erratic plant sizes. There is some corn ready to tassel this week along with some replanted corn three weeks old — there's a lot of variation in development.”
Patrick says one change in approaching corn borers is in using bucket traps. “The traps are new to us. Previously, we used the small, sticky traps. The buckets have worked great. For some reason, the borers seem to get into them much better.”
As far as he knows, there hasn't been any spraying for corn borers yet. “We think the moths we're seeing came out of overwintering,” says Patrick. “The winter was just too mild to take them out.”