New Bt corn hybrids and resistance issues
There have been new products added to the list of those containing Bt proteins for control of above and below ground insects. From Monsanto, there is Genuity VT Double Pro RIB Complete with Cry1A.105 and Cry2Ab2 for above ground insects, a product that is RIB, or refuge in the bag. These are the same genes in Genuity VT Double Pro (VT2P) but the refuge is now mixed within the bag at the 5% level. New products from Pioneer include Optimum Intrasect Xtra which contains Cry1F and Cry1Ab for above ground and Cry34/35Ab1 for below ground insects, and Optimum TRIsect which contains Cry1F and mCry3A, the first time that these two genes are together, also for above and below ground insects. Both of these products require a 20% refuge.
On another issue, we just attended meetings where rootworm resistance to the Cry3Bb1 gene that was discovered in the central Midwest was discussed among researchers, extension specialists, and the various seed companies. So far, resistance has not been seen with any of the other gene proteins. Of primary concern was how to handle corn plantings in future years in those areas where resistance developed. Resistance has NOT been found in Ohio rootworm populations. However, of importance to Ohio growers is to remind them of the continued potential for resistance to develop, and what we need to do to help prevent it from occurring in our state.
As discussed last August in the C.O.R.N. 2011-26 issue, growers should
1) rotate to another crop such as soybean (albeit keeping an eye out for the western corn rootworm variant),
2) ALWAYS PLANT THE REFUGE (remember that this is a requirement, which will automatically be planted if you use an RIB, or refuge in the bag, product),
3) if deciding to plant continuous corn, rotate among other rootworm management tactics such as using a soil insecticide, and
4) if wanting to continue to plant a rootworm Bt hybrid to control rootworm larvae, use a pyramided gene product such as SmartStax or rotate to a single gene product not containing the Cry3Bb1 gene.
It is to all our benefit if growers employ practices that will help to prevent resistance from becoming an Ohio problem!