That’s according to Bruce Battles, agronomy marketing manager with Syngenta Seeds, Inc., speaking on Friday at the 2008 Commodity Classic in Nashville, Tennessee. His remarks were part of a Learning Center session on protecting yield potential in continuous corn.
“Transgenic hybrids give you an option – other than cultivation – for controlling volunteer corn in continuous cropping systems, but that’s only if you rotate your herbicide-tolerant traits,” said Battles. “If you’re planting glyphosate-tolerant corn after glyphosate-tolerant corn, for example, you’re eliminating any postemergence spray option.” The same goes for planting LibertyLink® corn after LibertyLink corn.
While not as ugly as volunteer corn in a sea of soybeans, volunteers in continuous corn can cause significant yield loss. New evidence suggests that volunteers also may reduce rootworm protection from Bt hybrids by providing an alternate, non-toxic food source, said Battles.
In a 2006 University of Illinois weed control study at Urbana and DeKalb, volunteer corn reduced yield of glyphosate-tolerant corn by 42% and yield of LibertyLink corn by 60%.
“These plots were uniformly seeded with volunteer corn and are more reflective of extreme field situations where you might have had severe lodging/ear loss or the wrong combine setting,” said Battles.
To simulate infestations resulting from lodged corn, agronomists with Syngenta Agronomy Research seeded test plots in 2007 with either kernels or ears, at different densities, left over from the previous year. Yield losses from the heaviest density of ears (four ears per five row feet) was as high as 20%, whereas yield losses from individual volunteer plants at the same density was only 6%.
“The take-home message here is if you don’t plan ahead, volunteer corn can back you into a corner,” said Battles.
For 2008 planting, Syngenta trait offerings include double and triple stacks that combine the Agrisure® RW trait for rootworm control with traits for glyphosate tolerance and/or resistance to LIBERTY® (glufosinate) herbicide. New for 2008 is the Agrisure 3000GT quad stack, which combines rootworm and corn borer protection with resistance to both glyphosate and glufosinate herbicides.
“If you’re following a conventional hybrid, then you can use your choice of Agrisure GT/RW traits or Agrisure CB/LL/RW traits to expand your weed control options,” explained Battles. “If you’re following a herbicide-tolerant hybrid, then you need to rotate your traits or go with a stack like the new Agrisure 3000GT quad stack.”
Battles said planting back to soybeans every third or fourth year is an effective way to break the weed and disease cycles of continuous corn while allowing for clean-up of glyphosate-tolerant and glufosinate-tolerant volunteers with alternate chemistries like Fusion® and Fusilade® herbicides.