First generation European corn borer makes for some pretty easy scouting. We were able to find first generation corn borer infestations in Western Illinois and are still finding them in Northern Illinois. Second/subsequent generations of corn borer require the crop scout to look for quarter inch sized egg masses.
It is of little wonder that even well trained crop scouts have a hard time detecting what can still be a yield-reducing pest in non-GM corn. Where the industry once thought corn borer to be “old news,” we now realize that it is “still news.”
Burrus even has the surveys to prove it. Each season, Burrus Account Managers examine indicator hybrids that we distribute in our multi-state show plot system. The rate the level of corn borer pressure as being low (1-5 borer infested plants per 25 surveyed plants), medium (6-10 borer infested plants per 25 surveyed plants), and high (11-25 borer infested plants per 25 plants). By examining their survey results over the last several years, Burrus has come to a few important conclusions. First, Burrus has concluded that corn borers have reached a new equilibrium point. They are surviving in enough additional non-corn host plant material that they now typically infest about 10 to 15 percent of surveyed corn Second, Burrus has mapped the area more prone to second/subsequent generation corn borer infestations. (Please note that the Hughes footprint was not included in the 2014 Survey.)
Our survey results indicate that corn borer is still a potentially destructive pest in some portions of the Burrus footprint (north central Missouri, western Illinois, southeast Iowa, and the Illinois River valley). Growers in these areas must always consider corn borer when making their hybrid decisions. At the very least, growers in those areas must be prepared to scout. Those interested in trying their hand at scouting for the second generation may want to watch last year’s Burrus Agronomy U session on European corn borer at https://www.youtube.com/watch?v=k1QvlzQ0TW0. The session briefly describes the egg-scouting technique used for second/subsequent generation corn borer and it also provides threshold guidance.