Sustainable Agriculture Literature Review - Boulder County

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Summary
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7. Pest Management
In the U.S., the amount (pounds) of applied pesticides has decreased from a highpoint in
the early 1980s and has remained relatively stable over the past few decades. Pesticides
are partially responsible for increasing the productivity of agriculture during the last century
and continue to be a critical factor in reducing crop damage. The overall reduction in
pesticide applications is attributed to several factors including quality improvements in the
mix of pesticide ingredients, increases in ability to target specific pests, improved pesticide
application methods and management from farmers, and high rates of adoption of
genetically engineered (GE) crops.
Despite reductions in overall pesticide usage, direct and indirect financial expenditures
remain high, with Colorado farmers spending roughly $113 million on pesticides in 2008,
or about five percent of operating expenses. Estimates of the external expenses, from
impacts including pesticide poisonings to humans, reduction of fish and wildlife
populations, livestock losses, honey bee losses, reduction of beneficial insects, and
increased pesticide resistance in weeds and insects have been placed at $8 billion
annually for the U.S. One of the most recent and profound changes to pest management
has been the high rate of adoption for GE crops since their introduction in 1996. The most
popular GE crops are those that contain pest management traits, either herbicide
tolerance or insect resistance. Roundup Ready®, and Liberty Link® maize are two
varieties of GE crops grown in Boulder County currently. Overall, the literature has shown
that GE crops can have environmental benefits due to generally decreased pesticide
usage and stimulation of soil conservation practices.
Estimates of the rates of pesticide use on transgenic varieties vary between crops and
production systems, but have generally been found to reduce overall applications in the
range of 3-15 percent, with some studies finding higher averages of 25-33 percent
compared to conventional crop varieties and systems. While the adoption of GE crops has
been shown to reduce the pounds of active ingredients of herbicides and insecticides, it
has also been found to increase the use of the specific type of herbicide that the
transgenic variety has been engineered to resist. A prominent example is a variety of
herbicide resistant (in this case glyphosate) soybeans, which have reduced the need for
overall quantity of non-glyphosate herbicides, but more than doubled the kilograms used
per hectare of glyphosate.
The increased reliance on pesticides in both conventional and GE cropping systems has
increased the development of pesticide resistant species, and now over 300 different
biotypes have displayed resistance to one or more herbicides or insecticides. At present
the North American Herbicide Resistance Action Committee and the Weed Science
Society of America (WSSA) have identified four different types of herbicide resistant
weeds in Colorado, at over 2,000 sites and infesting about 66,000 acres in the state. The
potential prevalence of pesticide resistance in weeds and insects was estimated in several
studies to have the capacity to decrease benefits of current chemical pesticides, requiring
more or different pesticides to achieve similar results in the future, and potentially negating
previous environmental and financial benefits. Integrated pest management (IPM) is
widely recognized as a method for reducing the use of chemical pesticides, while still
limiting damage from pests, though several authors note the slow rates of adoption and
local nature of methods as limiting factors to IPM being used more frequently.
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