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New report finds that herbicide-resistant crops have increased pesticide use (Wednesday, Oct. 27, 2004 -- CropChoice news) -- The following comes from the conclusions and future prospects section of a new report by Benbrook Consulting Services -- "Genetically Engineered Crops and Pesticide Use in the United States: The First Nine Years". "While the discovery and adoption of GE crop technology has changed
American agriculture in many ways, reducing overall pesticide use is
not among them. Bt transgenic crops have reduced overall insecticide
use, but HT crops have increased it by a far greater margin.
Moreover, the performance of HT crops appears to be slipping. The average acre planted to glyphosate-tolerant crops is requiring more
and more help from other herbicides, a trend with serious environmental
and economic implications. Resistance to glyphosate has emerged as a serious concern
across most of the intensively farmed regions of the U.S.
The number of resistant weeds and their rate of spread is not
surprising given the degree of selection pressure imposed on
weed populations by farmers applying glyphosate herbicides
multiple times per year, and sometimes year in and year out on
the same field. Resistant weeds typically emerge first on just a few isolated
fields, but their pollen, genes, and seeds can travel widely
and spread quickly, especially if glyphosate continues to be relied
on as heavily has it has been in recent years. This is why
both universities and some herbicide manufacturers are calling
for more aggressive, prevention-oriented management of resistance
to glyphosate. In the case of the weed marestail, the recent
focus on resistance management has come too late. No substantial change in the intensity of glyphosate use
in the U.S. is expected in the foreseeable future, given the continued
popularity of HT crops dependent on glyphosate, the limited
supply of non-HT seed in some popular varieties, and the
increasingly aggressive promotions offered to farmers relying exclusively
on Roundup Ready technology. As a result, marestail
will almost certainly be the first of several glyphosate-resistant
weeds that emerge and spread, triggering the need for additional
herbicide applications and eroding the cost advantage and
popularity of HT technology. The future of Bt transgenic crops is brighter, especially in
the case of Bt cotton. Several university and USDA researchers
are closely monitoring efficacy in Bt cotton, which appears to
have changed little over the last nine years. The attention focused
on resistance management, and the issuance of mandatory
resistance management plans, has proven effective thus far
in delaying the emergence of resistance. Indeed, some experts
now think that the emphasis on resistance management in Bt
cotton can be relaxed. History suggests that lessened diligence
in cotton insect resistance management efforts would be premature,
given that it has taken 10-15 years for cotton insects to develop resistance to each new type of insecticide applied to control them. This cycle
began with the organochlorines in the 1960s and 1970s, and then repeated itself
with the carbamates in the 1970s and 1980s and the synthetic pyrethroids in the
1980s and 1990s. Prudence dictates waiting until about 2010 before determining
whether contemporary resistance management plans are indeed working and might
possibly be simplified. Bt corn for control of ECBs and SWCBs remains highly effective but is also
almost certainly overused. Many farmers are planting these varieties as an insurance
policy against potentially damaging insect populations. In 2004, Monsanto introduced
its new Cry 3Bb Bt corn for rootworm management and by 2005, several
corn varieties will express both the Bt toxin targeted toward the ECB/SWCB and the
new toxin designed to manage corn rootworms. There has been virtually no field research or regulatory review of the ecological
and food safety implications when widely planted Bt corn varieties are simultaneously
expressing dual Bt genes. Current USDA and EPA approvals are based
on the assumption that the two Bt transgenes in corn plants will operate exactly as
they do in varieties engineered to express a single Bt gene, and that the impacts of
the dual transgenes will not in any way be additive or decrease the stability of gene
expression. These are significant and questionable assumptions that if incorrect,
could lead to major, unintended consequences. For this reason, these assumptions
should be subjected to empirical study before widespread planting of dual- Bt varieties
is authorized." The full report is available at http://www.biotech-info.net/technicalpaper7.html | |
