Wednesday, December 3, 2014

Non-GMO Corn Growers Need to Watch Out for Corn Borer


Non-GMO corn impacted by European Corn Borer in Burrus Footprint (orange-heavy infestations and yellow-moderate infestations)
European corn borer appeared once again, it appears that some of those infestations rivaled 2013’s severe levels.  For some growers that meant a loss of a couple to few dozen bushels.  For others timely rains minimized the impact of corn borer feeding.  

European corn borer first appeared in the United States around 1917 and the pest reached the midwest in the late 1930s/early 1940s.  The pest was so devastating that the University of Illinois began to conduct an annual fall corn borer survey.  Extension agents would drive through the countryside each fall, examining plants to determine percent infestation, and the number of corn borer larvae within each infested plant.  
The results of that survey (Figure 1), results that span about a 60 year timeframe. As seen in that diagram, infestations went “all over the place” from one year to the next.  There literally was not a relationship between one season’s infestation level and the next season’s infestation level. That all changed in 1996 when the advent of Bt corn initiated a steady decline in corn borer damage. 

As can be seen (Figure 3,4, & 5), the adoption of Bt corn was dramatic and steady.  Within a decade, Bt hyrbids were planted on about 40% of midwest corn acres.  Within a decade and a half, Bt hybrids were planted on about 65% of Midwest corn acres.  The reasons for adoption were very clear, Bt hybrids minimized the use of insecticides (products that growers hated to use), minimized spillover effects (injury to non-target species, contamination issues, etc.), and effectively/efficiently controlled European corn borer,  then the number one pest of Midwest corn.  By 2010, the pest had been so injured by the use of Bt products that the University of Illinois discontinued its annual fall survey.  
  
Burrus Account Managers have conducted their own survey of non-GM/only herbicide tolerant products each season.  Our survey is very different from that one conducted by the U of I because we do not randomly select fields.  Instead, we examine non-insect traited hybrids to determine what the “background noise” for European corn borer looks like (i.e. we annually get a feel for what type of injury corn borers might have inflicted if a grower was not using insect traited products).   On some test plot results, the corn borer infestation is noted.  
   
 The 2009 growing season marked the “low point” for moderate to severe infestation, but since that time our Account Managers have consistently detected moderate to severe corn borer infestations above 10% (sometimes even above 20%).  For this reason, Burrus warns non-GM growers that European corn borer was still a very present danger, cautioning that future growing seasons might provide a repeat of the 2013 and 2014 story.   

As can be seen in Figure 5, our surveys currently point toward levels of moderate to severe infestation roughly similar to that experienced last growing season. The likelihood of occasional severe infestations means growers must vigilantly scout their fields for European corn borer (definitely within non-GM corn but also within traited hybrids,  just in case resistance ever develops).  At least two (some would say more than two) generations of corn borer occur each growing season and the scouting techniques for both are very different.  

While both generations can be damaging, the second generation seems to be the one that most growers miss.  Burrus encourages our customers to scout their fields every few days next year and to contact their local Account Manager or Sales Agronomist should there be questions.

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