Rootworm Resistance Wilting?

Pest-resistant corn varieties may have reached their expiration date. 

The rundown: Bt corn, notable for fighting rootworm infestations since 2003, has had less luck over the decades. A recent study from Purdue University found the overuse of genetically engineered corn has become a long-term detriment. 

Some more context: Broad adoption in 2004 of Bt corn, which is genetically modified with the bacterium Bacillus thuringiensis, reduced pest pressures across the Corn Belt. Consequently, continual corn planting in the following decades led to reports of rootworms becoming resistant to the toxin. 

Researchers say part of the reason could be that some states rely on Bt corn when they don’t have to. Rootworm infestations led to a 47.5 bushel-per-acre yield reduction within western states between 2014 and 2016. Losses only accumulated to an 8.5-bushel reduction in eastern states, where rootworm has been less of an issue.

Soundbite: “If you think of a Bt hybrid as a finite resource, like a declining debit card, every time you use it, you erode a little bit of susceptibility. So it’s a little less likely that it will work as well next time.” — Christian Krupke, Purdue professor of entomology 

Farmers want the biggest bang for their buck. That often means selecting the best seed, which might also include the Bt trait. Unfortunately, the added cost of planting GM seeds might lead to a bigger long-term price tag. Michigan farmers alone could experience lifetime losses adding up to $1.6B.

Researchers say Bt corn can still be effective, but maintaining normal crop rotations in an operation can help lower the risk of Bt-resistant pests.