December 15, 2008
Expansion of corn acreage to meet ethanol targets is reducing the
ability of beneficial insects to control pests, a loss valued at $58
million in the four states studied (Michigan, Iowa, Minnesota and
Wisconsin), report researchers writing in the journal Proceedings of
the National Academy of Sciences.
"Corn is a less favorable habitat for many ladybird beetles
(ladybugs) and other beneficial insects that feed on pests such as
the soybean aphid," said Doug Landis, a professor of entomology at
Michigan State University and lead author of the study. "As we plant
more corn, we reduce the ability of that landscape to supply
beneficial predators to control pests in soybeans and other crops.
This results in increased pesticide use and yield losses. This
research estimates the value of this biological pest control service
in soybeans (in the four states) to be about $240 million each year."
Estimated annual value of natural biocontrol services against soybean
aphid in 4 north-central U.S. states under a crop landscape typical
for the period 2005–2006 and under a biofuel-influenced landscape of
increased corn. Value of biocontrol services for IPM in millions of
dollars based on a 2007–08 projected soybean price of $380 per ton
and using actual 2007 corn ha increases per state.
"Over-reliance on any one crop is likely to reduce the value of
natural control of pest insects by beneficial insects," added Scott
Swinton, professor of agricultural, food and resource economics at
Michigan State University and a co-author of the paper. "If we look
at farmers who grow only corn and soybeans, increasing corn acreage
and reducing soybean acreage will probably mean higher costs for
soybean pest control. Beneficial insects help control pests so
growers have lower pest control costs."
The researchers estimate that corn acreage increased by 19 percent in
the United States from 2006 to 2007, reducing landscape diversity.
More acreage will be needed to meet the ethanol production targets
mandated by congress.
"Ultimately, we hope this helps policymakers think about which and
how much of any biofuel crop, as well as the location of the crop,
makes sense for a particular landscape," Landis said. "We could
choose to create monocultures of a single biofuel crop or have
diverse mixtures of many biomass sources including perennial trees
and grasses as well as corn. Diverse landscapes often support higher
levels of vital ecosystems services such as pest suppression and
pollination. Our goal is to provide information so people can make
more informed decisions."
Earlier research has shown that a diverse landscape of native
perennial grasses and other flowering plants can yield higher amounts
of biofuel per acre that corn or soy, with less need for water,
fertilizers, or pesticides.
Douglas Landis, Mary Gardiner, Wopke van der Werf, and Scott Swinton.
Increasing corn for biofuel production reduces biocontrol services in
agricultural landscapes. PNAS Online Early Edition the week of
December 15-19, 2008
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