DiFonzo told DTN she was impressed with the changes Pioneer made this year.

"They've gone about as far as they can go," in correcting the problem, she said. "I think it's probably the most honest and correct change, and I think it should be message to growers that [Pioneer is] really trying to manage this pest in the right way."

Pioneer Media Relations Manager Susan Mantey added that Pioneer has informed its Cry1F licensees of the change, with the expectation that they will follow suit in their own marketing materials.

CONFLICT BETWEEN SCIENCE AND MARKETING

Previously, both Pioneer and Dow maintained that Cry1F failures were a sporadic and local problem, and made only minor changes to their 2017 marketing materials. See the DTN story here: http://bit.ly/….

Pioneer's latest comments suggest its own research into the problem in the interim led to a change of heart.

"DuPont Pioneer research shows a wide-spread decrease in susceptibility in many western bean cutworm populations, indicating the possibility of field evolved resistance to Cry1F in most geographies," the company said in its statement to DTN. "While some growers will experience some benefit, farmers should not depend on the Cry1F trait providing an acceptable level of control."

Dow issued a similar statement, saying: "We constantly review the scientific information available to us from internal research, the academic community, and our customers, all of which indicate that making a change to market positioning, as Pioneer is doing, is prudent. Dow AgroSciences and our licensees are in the process of making similar changes to our marketing materials to set appropriate expectations for our customers and ensure they can manage the pest with the best available tools."

The Cry1F trait never provided reliable control of the western bean cutworm, entomologists have noted. It was designed and brought to market to target the European corn borer in 2001. Only later, in 2003, was western bean cutworm added to the trait's marketing language when it emerged as a more serious pest of corn.

Pioneer scientists never claimed that the Cry1F trait fully controlled western bean cutworm.

"Baseline susceptibility studies conducted in the early 2000s suggested that western bean cutworm is moderately susceptible to purified Cry1F protein and variation in western bean cutworm susceptibility to the Cry1F protein in field populations was high and expected even before there was widespread use of Cry1F-expressing maize hybrids," Pioneer scientists wrote in a 2015 study on Cry1F's control of western bean cutworm in Nebraska.

Overall, the scientists conclude that Cry1F hybrids "demonstrated varying levels of moderate control, but not immunity" to the western bean cutworm.

Even EPA acknowledged this lower level of protection when it first allowed western bean cutworm to be added to the Cry1F marketing language. "EPA determined in 2003 that Cry1F would likely suppress but not control Western bean cutworm because the trait was not high dose," the agency told DTN in an email.

The new language from Pioneer (and soon Dow) for Cry1F is unprecedented in the world of Bt trait marketing, DiFonzo noted. Companies have never altered their marketing language to account for Bt resistance before -- not even with traits like Cry3Bb1 (YieldGard), which has been widely compromised in the Midwest by western corn rootworm resistance.

"This is uncharted territory," DiFonzo said. "I haven't seen anything like this change before with a trait."

For a comprehensive list of Bt traits in corn, including which ones may be compromised by pest resistance, see DiFonzo's Handy Bt Trait table here: http://bit.ly/….

Emily Unglesbee can be reached at Emily.unglesbee@dtn.com

Follow Emily Unglesbee on Twitter @Emily_Unglesbee

(GH/ES)