Corn hybrid selection is about more than maturity and agronomic properties.
Many corn hybrids also come with a package of Bt traits for the management of various insects
below-ground (for example corn rootworm) and above-ground (for example, corn borer) pests.
These traits can add substantially to the cost of the seed so it’s worth evaluating which ones you really
need. In fields without a consistent history of insect pest pressure Bt traits are an added cost that
likely won’t pay for itself.
Sometimes you only need protection against soil pests, sometimes against above-ground pests, and
sometimes neither. But how do you know what Bt traits the various hybrids contain and what insects they
are meant to manage? This can be confusing or hard to figure out.
Bt Resistance is arguably the most important issue facing growers, extension entomologists, and seed
company agronomists. Problems continue to increase in regions where field failures were already found,
and new cases of resistance are reported every season.
To date, resistance is confirmed to all Bt toxins targeting western corn rootworm, particularly in the
central corn belt. In the southern states, corn earworm and fall armyworm resistance is expanding, while
Cry1F no longer controls western bean cutworm in the Great Lakes region.
These species were once secondary to European corn borer in importance, but now they are of primary
concern for many growers. It is critical to be up-to-date on resistance development in your local area
so that you know the limitations of the Bt traits you plant.
There is an excellent resource available to help with this – the Handy Bt Trait Table. This invaluable
reference is written by Dr. Chris DiFonzo at Michigan State University and is updated every year.
In one place it lists what types of Bt are present in which corn hybrids, what insects they are targeted
for, and for which insects’ resistance to a given Bt protein has been documented (leading to a loss of
efficacy).
Find the Handy Bt Trait Table linked on the OSU Ag Insects website. https://aginsects.osu.edu/
Check it out to learn which Bt traits are in which hybrids so you can make the most informed and
economical decisions for your farm.