Do I Need to Worry About Rootworms in 2015?

I have been asked a lot about corn rootworm survival this season primarily about our wet June during traditional hatch times.  In 2014, we had a hard cold winter that carried into planting with cool wet conditions during and after planting.  June was especially wet with saturated conditions up to just after July 4th. 

"So we had an overall lethal crop year for corn rootworm larvae and eggs right?"  In most cases that would not be accurate.  While we had severe cold with air temperatures in the -20F to -30F range for spells this winter, we still had very adequate snow cover that kept soil temperatures above zero all winter and in most cases it was closer to 10-15F above zero at the coldest.  These soil temperatures and the snow cover likely kept most rootworm eggs viable over winter. 

"Ok, ok . .  the saturated soil conditions in June had to at least kill most of the remaining beetle eggs and larvae right?"  That's also not entirely likely as beetle emergence and hatch was delayed a couple of weeks by cool conditions.  Remember that corn rootworm egg hatch is closely tied to GDD accumulation during the growing season.  They also don't all hatch at once, it is extended over about a months time during the summer.  While saturated conditions will potentially kill hatching larvae, it will not kill eggs so if hatch was delayed to after the soil was saturated it likely didn't kill many of them. 

"Well that can't be right, I didn't see any beetles scouting fields at silking or just after the completion of pollination."  This was very true in 2014, I rarely ran into many beetles during pollination this year.  I did however, start seeing them during grain fill and continue to notice more beetles than normal as we move closer to harvest.  As we dug roots later in the season this year I have noticed significant feeding in areas of continuous corn, especially on single RW traited corn without insecticide.  In one instance we have noticed plant lodging on single traited corn next to straight RR corn treated with Force insecticide.  Do we have resistance issues, I don't think so at this time as it is more a result of pressure on COC acres than resistance but will need to be monitored in the future.

One observation over the past two months has been a significantly higher population of Northern Corn Rootworm than I have seen in the past.  This is alarming due to the ability of Northern's to exhibit extended diapause meaning they can hatch later or in some instances two growing seasons later.  So for 2015 I think that in COC we will have to consider dual modes of action in RW traits or at the very least insecticide on single traits.  There is some elevated concern on rotated acres, but I think we are a year out before we see these Northerns cause major problems in rotated fields.  With a potential for lower traited corn and reduced insecticide use at lower corn prices I think we will find out just what kind of pressure we have in 2015.  I wouldn't count out rootworms being a major pest in 2015, they may surprise us all as they have in the past.