In one word…insurance. The era of stout grain prices has turned integrated pest management into insurance pest management, which worries entomologists. And since the billion-dollar-robbing rootworm is driving fear in continuous corn and continuous single Bt-RW trait country, who wouldn't want to protect every ear from falling to the ground – especially when research can show a profitable yield advantage with soil insecticides.

"Farmers in continuous corn areas are seeing a lot more lodging and root pruning, and they aren't certain why," says Joe Short, Midwest marketing manager for Amvac, the leading marketer of corn soil insecticides in the U.S. We're seeing higher populations, increased tolerance and hybrid trait resistance among rootworms and more infested acres, he says.

Amvac, maker of Aztec, Counter, SmartChoice and Force 3G in SmartBox, has seen a dramatic increase in use of corn insecticides. In 2012, treated acres rose 30% over 2011, reaching 10-11 million acres – which was on top of 10% growth during 2011. "For 2013, we're estimating a 40% increase over last year, to reach 14-15 million treated acres," Short says.

Ironically, the advent of these in-plant Bt-RW traits was planned to drastically reduce soil insecticide use (except for refuge acres), down from a high of 30-32 million treated acres before traits. And now treated acres have reached half that amount.

University research in eight states has shown that corn insecticides pay their way in 73% of the trials comparing insecticide treated versus untreated rootworm hybrids, according to the company. Average yield increase range is 5-10 bu./acre, which is above the product cost equal to 3-4 bu./acre. But entomologists are also quick to point out that this yield increase can be skewed since research trials are usually placed in fields with heavier than normal rootworm populations.

And despite the yield savings, university entomologists worry that soil insecticides may not reduce resistant populations due to rootworms surviving outside of the soil insecticide zone, and could actually increase beetle emergence and more rapid spread of resistance, according to Illinois Entomologist Gray.