Word on the street is there will be many more corn refuge checks in 2012 in cotton growing regions. This is due to decreasing compliance over the last couple of years. However, it is getting so complicated that one grower told me this week as I explained it to him. “Forget it”, it is easier for me to just put cotton on those 500 acres I was going to put in corn. So here is the challenge for cotton growing regions.
Corn that contains two Bt genes for above ground pest (leps) is only required to have a 20% non Bt refuge planted within ½ of the Bt. This will include hybrids that express traits such as Monsanto’s VTP, Pioneer’s Optimum Intrasect, or Agrisure Viptera 3110. The problem is that the availability of hybrids containing these traits are limited in the south right now, so currently we are planting mostly VT3, VT3P, Herculex, and some Agrisure 3111 and Herculex Xtra. Out of “this” grouping the VT3P, Herculex Xtra, and Agrisure 3111 require a 20% refuge and the VT3 and Herculex require a 50% refuge. It is not uncommon to have both on the same farm. However, here is the “kicker” that is causing even more confusion for corn growers in cotton regions: The VT3, VT3P, Herculex Xtra, and the Agrisure 3111 also contain a Bt corn rootworm gene that we don’t need in most areas of the south and it requires that the refuge has to be in the same field or immediately adjacent to the Bt corn instead of within ½ mile that most growers in the south have become accustomed to.
A frequent question that I have been asked a lot lately is, “what about just putting non Bt seed in 2 hoppers and stripping the field (keep in mind that refuge for rootworm traited corn has to be at least 4 rows wide)? That is a great idea and is actually recommended by the companies as one option. However, in the South where we commonly have to treat our refuge acres for southwestern corn borer, that would require treating a whole field including the Bt portion for corn borers which is not needed or practical. Do you see how confusing this can be for growers? This is also one of the reasons “refuge in a bag” option is being talked about for the South.
The table below list most of the traits or trait packages available in corn and the refuge requirement associated with that trait. Under the Target Pest column, if you also see rootworm listed, the refuge has to be in the same field or adjacent to the Bt corn. If it does not say rootworm under Target Pest column, the refuge can be up to ½ mile distance from Bt corn. This table can also be found on page 47 on the 2012 Insect Control Guide for Agronomic Crops under the publication tab at the top of the page. Bottom Line: If your not sure what to do, ask someone with the company or your local Extension Service.