A Future Of Seed Mixtures In The Corn Belt Seems Certain: Potential Consequences
URBANA, ILL.
The U.S. Environmental
Protection Agency (EPA)
has given regulatory approval
to several companies to
move forward with the full-scale
commercialization of Bt
hybrids in which a seed mixture
forms the basis of resistance
management. A paper
was recently published in the Journal of Economic
Entomology (Vol. 104, No. 2, pp. 343-
352; DOI: 10.1603/EC10388) titled “Seeds of
Change: Corn Seed Mixtures for Resistance
Management and Integrated Pest Management.”
The lead author is David Onstad, a professor in
the University of Illinois Department of Crop
Sciences. David is an internationally respected
modeler and has been instrumental in developing
models that help the scientific community
and the EPA better understand how resistance
to Bt corn may develop. Provided are some summary
quotes from this important and timely article.
•
“We conclude that seed mixtures will make
pest monitoring more difficult and that seed
mixtures may make IRM [insect resistance
management] riskier because of larval behavior
and greater adoption of insecticidal corn.”
• “Conversely, block refuges present a different
suite of risks because of adult pest behavior and
the lower compliance with IRM rules expected
from farmers.”
• “This risk-management approach to corn
pest management has certainly provided tangible
benefits to producers in corn-producing regions
where target pests were once abundant,
as in the case of Bt corn hybrids targeting European
corn borers. However, this approach
carries with it the tendency to ignore many aspects
of IPM, such as monitoring pest levels and
concentrating treatments when or where appropriate,
because there is an assumption that
most pests are controlled throughout the season,
regardless of pressure levels. Although field
corn has never been considered an IPM-intensive
cropping system, there is less impetus than
ever for growers or crop consultants to enter
fields.”
• “We expect that growers will have fewer
choices in what hybrids they grow in their fields.
Therefore, from the perspective of overall IPM,
we are concerned that seed companies will provide
fewer options for regional needs, secondary
pests, disease control, and refuge plantings.”
• “We question whether pyramided toxins will
actually increase mortality in targeted pests.
Without this increase in mortality through independent
activity of each toxin, the pyramid
has much less value for IRM. The U.S. Environmental
Protection Agency recently acknowledged
that a corn hybrid pyramided with two
toxins active against corn rootworms does not
significantly increase larval mortality.”
These statements are worthy of reflection as
the industry transitions to the new paradigm of
95-to-5 seed blends across the Corn Belt. The
authors of this paper represent a diversity of our
land-grant institutions: University of Illinois,
University of Wisconsin, University of Minnesota,
Purdue University, Michigan State University,
Iowa State University, Kansas State
University, and Penn State University. Scientists
from additional organizations contributed
to the article, including the USDA-ARS, the Illinois
Natural History Survey, and the Ontario
Ministry of Agriculture.
Another significant consequence of the seed
mixture infrastructure emerging within the corn
insect protection arena is increasing pressure
on the long-term sustainability of the soil insecticide
market. As the number of refuges configured
as blocks, strips, or separate fields
declines, soil insecticide use should also be reduced.
Ultimately, loss of soil insecticide products
will result in a reduced flexibility for
producers to effectively manage economic infestations
of white grubs, wireworms, and other
soil insects. In addition, if resistance develops
to Bt hybrids and becomes widespread, growers
will need to have some remaining tools to manage
insect pests of corn. It remains to be seen
whether some groups within the agribusiness
sector are interested in maintaining their investments
in this competitive arena just in case
resistance develops or to offer products targeted
against secondary soil insect pests. Δ
DR. MICHAEL GRAY: Professor, Crop Production,
University of Illinois