By Erin Hodgson
While going through the extension winter gauntlet, I talked a lot about corn rootworm. It is one of most important pests in the Midwest and should be on your mind when deciding on hybrids and insecticides. I often got questions about using stacked and pyramided corn hybrids, and there seemed to be some confusion about the terminology.
When it comes to transgenic corn here in Iowa, you have a variety of transgenic proteins that express insecticidal properties. Specifically, the protein toxins come from a bacteria called Bacillus thuringiensis, or commonly known at Bt. There are four Bt proteins that attack corn rootworm larvae belowground: Cry3Bb1, Cry34/35Ab1, mCry3A, and eCry3.1Ab. There are five Bt proteins that attack a variety of caterpillars aboveground: Cry1Ab, Cry1F, Cry1A.105, Cry2Ab2, and Vip3A.
A pyramided hybrid includes two or more Bt traits attacking the same pest. An example of a pyramided hybrid would be Agrisure Viptera® 3110 (Cry1Ab + Vip3A). A stacked hybrid would include one aboveground Bt trait and one belowground Bt trait. An example of a stacked hybrid would be Optimum TRIsect® (Cry1F + mCry3A). There are stacked and pyramided corn that included at least two belowground and two aboveground Bt traits. An example of a stacked, pyramided Bt hybrid is Genuity SmartStax® (Cry1A.105 + Cry2Ab2 + Cry1F + Cry3Bb1 + Cry34/35Ab1).
As new corn hybrid products come on the market, they will often include a stack, pyramid or both. But the options change quickly and the proteins included aren’t always obvious in seed catalog descriptions. This 2015 BtTrait Table.pdf is a useful document that explains the different combination of Bt traits in corn.