As companies such as Dow Agrosciences, Monsanto and Pioneer push forward with corn seed mixtures that incorporate a 5% refuge in the bag, refuge compliance may soon be a concern of the past.
However, a multitude of scientists recently released a paper that examines the academic differences between insect resistance management in a block refuge versus a seed mixture scenario. Published in the Journal of Economic Entomology, the authors contend there are resistance risks inherent to both refuge systems.
Early on, the article contends scouting and monitoring insect populations will be a more difficult proposition in seed-mixture fields. Most seed mixture products will include a seed treatment on every kernel. With the insurance of Bt and insecticidal seed treatment on every acre, University of Illinois' David Onstad expects less attention will be paid to these fields, unlike a 20% refuge in adjacent fields.
In conjunction with less scouting, entomologists are concerned less attention will be paid to secondary pest outbreaks, such as corn earworm and armyworms. This could shift around the status of some pests. However, Onstad says different regions of the Cornbelt are on higher alerts for what many consider secondary pests.
Onstad also notes seed mixtures could change the pest landscape by affecting the natural enemies of many crop pests. Though, he admits this is primarily a scientific concern and most farmers do not expect pest control via natural predators.
"Entomologists have always hoped natural enemies would play a larger role, but that has not been the case in corn production," Onstad adds.
Lastly, the article notes block refuges may be at more risk for adult behavior to result in resistance development. Conversely, seed mixtures could come with a higher risk of promoting resistance in larval populations.
Monsanto's insect resistance management lead, Graham Head, says the company has been working for more than a decade to quantify the risk for insect resistance to Bt traits as a result of seed mixtures. In the end, human behavior is paramount when protecting Bt's usefulness.
"This technology removes the complex decisions that come with planting a refuge at a time of the year when growers are already short on time," Head explains. "It removes the concerns for refuge compliance. When you take everything into account, this comes with less uncertainty."
With regard to monitoring for pest outbreaks, Head says it's not more difficult to scout and monitor, it's simply different. As for secondary pests increasing in importance, he points out that Monsanto is in business to develop products the grower needs. Thus, secondary pest status monitoring is high on their list.
Lastly, Head expects growers will see Refuge in the Bag product yields comparable with the company's Genuity SmartStax products, which require a 5% structured refuge.
With the refuge plants interspersed with Bt plants in the RIB products, Head says they will be somewhat protected. At the same time, Head says that "protection" can't work too well, or the risk for pests developing resistance only increases. With RIB set for commercialization next year, Head is confident the company has struck the perfect balance between resistance and yield protection.