ngin - Norfolk Genetic Information Network

GM crops aren't working:
GM doesn't reduce spraying on Bt corn


Genetically engineered Bt crops have been hailed by the pro-biotech
lobby as the ultimate in environmental friendliness because these'plant
pesticides' supposedly reduce the need to spray millions of gallons of
toxic chemicals.

Below please find an interesting piece by Charles Benbrook regarding
genetically engineered Bt corn which shows that, in fact, "there has
been little change in corn insecticide use, despite the planting of
millions of acres of Bt corn in recent years."

Current state of play on bt corn, then, seems to be:

1. Bt corn is unproven agronomically:

Dr Erick Larson (Missippi State University Extension Service, Agronomy Notes 15 March, 1999):

"Bt corn hybrids [GE corn] are an unproven technology in the South. Bt corn should effectively control Southwestern and European corn borers and have moderate control on corn earworms and fall armyworms. However, data does not support whether hybrids containing this technology will yield well and have the agronomic characteristics similar to the best conventional hybrids in Mississippi. Considering the significant problems experienced with transgenic traits in other crops during the last several years, growers should be extremely cautious of any unproven technology."

2. Bt corn hasn't reduced spraying (see below)

3. Bt corn pollen appears toxic to some non-target species
(eg the Monarch butterfly)

4. Bt corn's final impact on human and animal health can only be guessed at

What, one wonders, would constitute a problem for this miraculous
technology?! And why are its proponents so incapable of telling the

A Monsanto Press Release of May 21, 1999 on the impact of Bt-corn
on Monarch butterflies states that:
"-- In 1998 use of Bt insect-protected corn reduced or eliminated
the use of broad spectrum chemical insecticides on some 15
million acres of U.S. farmland."

On May 19, 1999, the U.S. Department of Agriculture's National
Agricultural Statistics Service (NASS) released the results of
the 1998 field crop chemical use survey. The data can be
downloaded by anyone from the NASS site, go to
to May 1999, and then to May 19 ag cemical survey.

Nationwide on corn, the following insecticides were applied. The
percent following the active ingredient is the percent of
71,400,000 corn acres that were treated. In most cases, the
target pest is known and listed. As is well-known and obvious to
anyone, including Monsanto, the vast majority of corn insecticide
use is pre- or at plant for control of corn rootworms, cutworms,
and other soil insects. These applications are early in the year
and pose very little risk to Monarchs. As anyone also knows,
there has been little change in corn insecticide use, despite the
planting of millions of acres of Bt corn in recent years.

1998 U.S. Corn Insecticide Use (NASS data)
active ingredient  treated US     target insects
                   corn area [%]  of insecticides with a.i.
bifenthrin              2%        rootworms, soil insects
carbofuran              1%        ditto
chlorethoxyfos          1%        ditto
chlorpyrifos            6%        ditto
cyfluthrin              3%        ditto
dimethoate              1%        possibly ECB*
fipronil                1%        rootworms, soil insects
fonofos                 1%        ditto
lamba-cyhalothrin       2%        some for ECB
                                  most soil insects
methyl parathion        1%        rootworms, soil insects
permethrin              2%        possibly part for ECB
tebupirimiphos          3%        rootworms, soil insects
tefluthrin              5%        ditto
terbufos                6%        ditto

It is clear from the above that at most, Bt-corn may have reduced
corn insecticide use by 1% to 2% of corn acres, or 714,000 to 1.4
million acres (NASS surveyed 71.4 million corn acres in 1998).
Monsanto's claim of reducing or eliminating pesticide use on 15
million acres -- i.e. all acres planted -- is not accurate. Some
people on this list have asked why Monsanto seems to be such a
lightning rod for criticism. Statements like the one above is one
reason why.

In 1998, 14 insecticide with 4 active to eliminate ECB were
approved in Germany.

a.i.          insecticide      human      beneficial arthropod
                               toxicity   toxicity
permethrin    Ambush       + 5    Xi         no data
cyflutrin     Baythroid 50 + 1    Xn      harmful for all
deltamethrin  Decis liquid + 1    Xn      ditto   
B.t.k.        Dipel        + 3    not     not harmful for 6
                                harmful   tested species

7 of the above listed 14 a.i. approved in the U.S. are not
approved in Germany (bifenthrin, chlorethoxyfos, fipronil, 
fonofos, lamba-cyhalothrin, methyl parathion, tebupirimiphos).
The "dirty" insecticides - toxic and highly toxic to humans -
have been abandoned for use in corn to fight ECB. Farmers
alternatively make use of biological pest control (Trichogamma,
parasitic wasps) or plough the corn remains in autumn to
interrupt the ECB life cycle.]

May 25:
In light of the interest in the effects of Bt-corn on insecticide
use and European corn borer management, I compiled official USDA
data on insecticide use on corn for 1971, 1982, 1991, 1995, 1998.
With the help of Dr. Mike Gray, Univ. of Illinois corn IPM
specialist, I divided all active ingredients into three
"principle target pest" groups -- rootworm complex, European corn
borer, or rootworm plus (usually first generation) European corn
borer. I attributed one-half the acreage treated with products
applied for both rootworm and ECB to ECB management. I added the
percent acres treated across products.

The results show that:
* about 1 in 6 acres treated were sprayed for ECB in 1971, but by
  1998 about 1 in 3 acres treated were sprayed for ECB control.
* Total acres treated for all corn insect pests declined modestly
  through 1995, but is up in the last 3 years: 36.4% of national
  corn acres were treated in 1971, 35.8% in 1982, 34.2% in 1991,
  30% in 1995, and 33% in 1998.
* Acres treated for ECB rose from 9.5% in 1995 to 10.5% in 1998,
  despite the planting of some 15 million acres of Bt-corn. As
  many entomologists have pointed out, the introduction of Bt
  corn has heightened farmer attention to ECB damage, and many
  farmers are both planting Bt-corn on some acreage and spraying
  other acres than in the past would not have been treated. But
  clearly, Bt corn has not reduced insecticide use, and indeed
  probably has and will continue to increase it. This is not the
  fault of the technology, nor a reason to condemn it, it is just
  a fact. It does raise questions with the continued claims of
  some manufacturers who seem determined to stick with the
  "reduces insecticide use" argument.
* Rootworm acres treated also were up a little, from 15% in 1995
  to 17.5%, largely because of the change in Western corn
  rootworm behavior.

More details on these data and trends in corn and soybean pest
management systems and pesticide use will be in a forthcoming
report I am working on with colleagues in Consumers Union.


Charles Benbrook                   208-263-5236 (voice)
Benbrook Consulting Services       208-263-7342  (fax)
5085 Upper Pack River Road (e-mail)
Sandpoint, Idaho  83864