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2-Plants: No significant yield differences with GM crops according to USDA analysis

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TITLE:  No significant yield differences with GM crops according
        to USDA analysis
SOURCE: Union of Concerned Scientists, by Jane Rissler
        sent by The Edmonds Institute, USA
DATE:   June 30, 1999

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USDA Analysis of Genetically Engineered Crops
Shows No Significant Difference in Yield
in the Majority of Crops and Regions Surveyed
an analysis by Jane Rissler of the Union of Concerned Scientists
forwarded with her permission by the Edmonds Institute

The USDA Economic Research Service (ERS) has just released new
data on the benefits of genetically engineered (GE) Bt and
herbicide-tolerant crops. The new report, "Genetically Engineered
Crops for Pest Management," contains data on pesticide use on GE
crops in 1997 and yield of GE crops in 1997 and 1998. The report
is available at

Below I have summarized what I learned from the report. My
summary is somewhat different from the ERS summary--which
emphasized only the results supporting the view that
biotechnology is good for the environment and good for farmers.

The data reveal a mixed picture of benefits from crops engineered
to control pests. In some engineered crops in some regions,
pesticide use may be reduced and/or yields may be increased. But
in the majority of crops and regions surveyed, there are no
statistically significant differences in pesticide use or yield
between engineered and nonengineered varieties. In one case,
pesticide use increased on the engineered crop and in another
case, yield declined in the engineered varieties.

The ERS collected data on pesticide use in the 1997
growing season in several growing regions on the five most widely
planted engineered crops: Bt corn and cotton, herbicide tolerant
corn, and herbicide(glyphosate)-tolerant cotton and soybeans. All
together data were collected on 12 region and crop combinations,
i.e., Bt corn and HT corn in the Heartland, Bt cotton in three
regions, HT soybeans in 5 regions, and HT cotton in 2 regions,
and their nonengineered counterparts in all the regions.

In the 12 region/crop combinations, 7 showed no statistically
significant differences in pesticide use on engineered versus
nonengineered crops. Four showed significant reductions in
pesticide use on the engineered versus nonengineered crops. In
one region/crop combination, Bt corn in the Heartland,
significantly more pesticides were used on Bt versus nonBt corn.

Bt corn
data only from Heartland (IL, IN, IA, parts of SD, NE,
MN, MO, OH, KY) The data on insecticide acre-treatments* for all
insect pests, including Bt-corn pests, showed no statistically
significant difference in insecticide use on Bt versus nonBt

Bt cotton
In the Mississippi Delta area, insecticide acre-treatment* for
all insect pests on Bt and nonBt cotton were significantly
different statistically--53% higher on Bt than on nonBt cotton.

- In much of the southeastern cotton-growing area, insecticide
  acre-treatments* for all insect pests on Bt and nonBt cotton
  were not significantly different.

- In the region encompassing the southwestern cotton-growing
  area, Florida, and parts of Texas, insecticide acre-treatments*
  for all insect pests on Bt and nonBt cotton were not
  significantly different statistically.

Herbicide-tolerant corn
In the Heartland, there was no significant difference
statistically between herbicide use on HT versus nonHT corn.

Herbicide-tolerant soybeans
Data from five growing regions showed a statistically significant
decrease in three regions (51%, 23%, 20%) in herbicide acre
treatments for HT soybeans versus nonHT soybeans. For two other
regions, herbicide use was essentially the same for HT and nonHT

Herbicide-tolerant cotton
- In the Mississippi Delta, there was no significant difference
  statistically in herbicide use between HT and nonHT cotton.
- In much of the southeastern growing region, herbicide use was
  significantly decreased on HT versus nonHT cotton (a 22%

*An acre-treatment is the number of different pesticides applied
per acre times the number of repeat applications.

The ERS collected yield data in 1997 and 1998 for 12 and 18
region/crop combinations, respectively. The crops surveyed were
Bt corn and cotton and HT corn, cotton, and soybean and their
nonengineered counterparts.

In 1997, yields were not significantly different in engineered
versus nonengineered crops in 7 of 12 crop/region combinations.
Four of 12 showed significant increases (13-21%) in yields of
engineered versus nonengineered crops (HT soybeans in 3 regions
and Bt cotton in 1 region). One--HT cotton in 1 region--showed a
significant reduction in yield (12%) compared with its
nonengineered counterparts.

In 1998, yields were not signifciantly different in engineered
versus nonengineered crops in 12 of 18 crop/region combinations.
Six crop/region combinations (Bt corn in 2 regions, HT corn in 1
region, HT soybean in 1 region, Bt cotton in 2 regions) showed
significant increases in yield (5-30%) of engineered over
nonengineered crops. HT cotton (glyphosate-tolerant) was the only
engineered crop which showed no significant increase in yield in
either region where it was surveyed. 

Jane Rissler, Ph.D.
Senior Staff Scientist
Union of Concerned Scientists
1616 P St., NW, Suite 310
Washington, DC 20036
202-332-0900 phone
202-332-0905 fax

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