The Triazine Herbicides

579 Pages·2008·63.107 MB·English

by  Janis Mc Farland, Orvin Burnside, Homer M. LeBaron

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All royalties from the sale of this volume will be contributed to the Weed Science Society of America Endowment
Fund to benefit ongoing research and education in areas of weed science and weed management.
Contributing authors include university, government and industry scientists, extension specialists, and growers who
have offered their unique insight into the history and development of the triazines and their impact on modem agri-
culture. We thank each of them for their contribution to the field and to our book. We also are grateful to the thou-
sands of scientists involved in research, education and extension work who have helped to advance the understanding
of weed science over the past 50 years.
We offer a special thanks to Doane Marketing Research, Inc. for permission to provide authors with informa-
tion from its AgroTrak databases, and to Syngenta Crop Protection, Inc. for support of our effort and for allowing
access to studies and data submitted to the US Environmental Protection Agency. We are especially grateful to Linda
Edgerton for her project management and editing skills, to Dr. Gene Hill for his research support, to Betty Brame
for her expertise in manuscript preparation, and to both Jeff Stabnau, Librarian for Syngenta Crop Protection, and
Richard Jensen, Science Librarian at Brigham Young University, for their assistance with literature references.
Note that the authors' views are not intended to represent those of their past or present employers or the organiza-
tions with which they are affiliated.
Foreword
By Dennis .T Avery, Center for Global Food Issues, Hudson Institute
'Growing more crops and trees per acre leaves more land for Nature. eW cannot choose between feeding
malnourished children and saving endangered wild species. Without higher yields, peasant farmers will destroy
the wildlands and species to keep their children from starving. Sustainably higher yields of crops and trees are the
only visible way to save both.'
.rD Norman Bourlaug
1970 Nobel Peace Prize laureate and father of the Green Revolution, in 'Growing
More per Acre Leaves More Land for Nature,' Center for Global Food Issues,
www.highyieldconservation.org
April 30, 2002
This is an important book containing a great deal of solid information about the triazine herbicides, one of the most
important families of chemicals that support human society and protect our wildlife.
Just as chemistry protects children from disease, farmers are using chemistry to feed twice as many people as
they did 50 years ago- without using more land. They have tripled the yields on the planet's best cropland using
high-powered seeds, chemical fertilizers, irrigation, and pesticides. Without higher yields, people would already have
cleared all of the world's 61 million square miles of forest to get today's food supply. Virtually every forest tree and
creature alive on the planet today owes its existence to high-yield farmers and their chemicals. If we ban the pesti-
cides, we almost literally ban forests and wildlife.
Pesticides have played a key role in the world's rising crop yields. As the authors in this book note, the Green
Revolution's plant breeding miracles and fertilizers might have failed to prevent massive human starvation and wild-
lands destruction if the higher yield potential of our crop fields had simply nourished more bugs and weeds.
Even though birth rates are dropping all over the world, thanks to increases in food security, affluence, and urbani-
zation, the world's population will probably exceed 8 billion (up from today's 6.5 billion) by 2030 and might reach
9 billion by 2050.1 Rising incomes indicate that we'll provide high-quality diets (resource-costly meat, milk, and fruit)
for perhaps 8 billion people in 2050, instead of for the one billion who can afford them today. There will even be a
pet food challenge, with perhaps 500 million companion cats and dogs in an affluent, one-child China alone.
Overall, we will need to harvest nearly three times as much farm output in 2050 as we harvest today- and we're
already farming half the global land area not under deserts or glaciers. Pest control will remain vital to both people
and wildlife.
Interestingly, if we chart the pesticide usage in various countries for the past 70 years alongside life expectancy,
they rise in parallel. At the same time, age-adjusted cancer risks for nonsmokers have been declining. The use of
chemistry in medicines and public health interventions has had more direct human health impact, but pesticides help
reduce the real cost of fruits and vegetables. That's vital, because the 25% of people who eat the most produce have
only half the total cancer risks of the 25 % who eat the least!
.rD Bruce Ames, who received the National Science Medal from President Clinton, documented that we get
100000 times as much cancer risk from the natural chemicals in the foods we eat as from the tiny traces of pesticide
on our foods and in our drinking water.
The Soil and Water Conservation Society of America has declared that modem high-yield farming is the most sus-
tainable in history. This is in substantial part because of pesticides, and particularly because of conservation tillage
made possible by herbicides.
You will read a great deal in this book about herbicides and soil conservation because the triazine herbicides have
helped create a soil conservation miracle. Soil erosion for thousands of years was the greatest risk to the sustainability
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of human society. The soils of the Mediterranean Basin were nearly mined in ancient times by plowing and low-yield
cropping. But because we have tripled crop yields, we need to plant less than one-third as much land to get our food
supply, and that lets us use the safest, least-erodible soils. (That's why my hilly, rocky Shenandoah Valley is now in
grass for dairy and beef cattle, while the corn is grown on the deeper, more level soils of the Corn Belt.)
Equally important, modem herbicides like the triazines allow us to substitute low-till farming systems for the
ancient, erosion-inviting 'bare-earth' farming techniques such as plowing, hoeing, and 'clean-fallow.' (Fallow keeps
land bare for a whole season with repeated tillage to reduce the number of lurking weed seeds.)
The development of herbicides that consistently and cost-effectively kill both grasses and broad-leaved weeds
through the crop-growing season has enabled farmers to adopt low-till farming on millions of hectares of land around
the world. Low-till farming cuts water runoff and soil erosion by up to 95% and can double the moisture retained in the
field for crop growth. Dr. Stanley Trimble of UCLA reported that the Coon Creek watershed (a famously erodible
hilly region in southern Wisconsin) is now suffering only 6% as much soil loss as it did during the Dust Bowl days of
the 1930s. Low-till farming systems have played a key role in enabling today's Coon Creek farmers to build topsoil
in the midst of the highest-yield cropping in the region's history.
Weeds are our real competitor for space on the planet, so there is no end in sight to our need for herbicides. To
those who warn that weeds are developing resistance to the various widely used herbicides, I say that resistance
makes it even more important to have a variety of herbicides on the shelves, ready for rotational use against the
weeds. We must encourage still more research in new herbicides with different modes of action. We must also main-
tain our use of those safe and effective herbicides already on the market. In fact, after a decade-long, comprehensive
scientific evaluation, the USEPA has recently reaffirmed the safety of two important herbicides in the triazine family -
atrazine and simazine.
It has been only a half-century since better weed-control technology allowed most of us to escape from the drudg-
ery of stoop labor. Without the triazine chemistry, there is little question that millions of us would have to go back
into the fields with short-handled hoes. Our society would today be substantially less sustainable and our wildlands
and wild species would face far greater pressures from the plows of low-yield farmers.
Only with weed control can we both feed our growing population and protect critical environmental resources.
List of Contributors
John .F Ahrens Beth Carroll
Connecticut Agricultural Experiment Station Syngenta Crop Protection, Inc.
Windsor Greensboro
Connecticut North Carolina
Philip A. Banks Allan J. Cessna
MARATHON Agricultural Environmental National Water Research Institute
Consulting Saskatoon
Las Cruces Saskatchewan
New Mexico Canada
.V Michael Barringer B. R. Christensen
Syngenta Crop Protection, Inc. En-Fate, LLC.
Greensboro Plymouth
North Carolina Minnesota
James .F Brady
G. Euel Coats
Syngenta Crop Protection, Inc.
Mississippi State University
Greensboro
Mississippi State
North Carolina
Mississippi
Leslie D. Bray
Dennis Cooper
Syngenta Crop Protection, Inc.
Centre for Toxicology and Department of
Greensboro
Environmental Biology
North Carolina
University of Guelph
Guelph, Ontario
Charles B. Breckenridge
Canada
Syngenta Crop Protection, Inc.
Greensboro
Cheryl Dando
North Carolina
En-Fate, LLC.
Plymouth
Robert S. Bretzlaff
Minnesota
Sielken and Associates Consulting, Inc.
Bryan
saxeT Malcolm D. Devine
Performance Plants, Inc.
Saskatoon
David C. Bridges
Abraham Baldwin Agricultural College Saskatchewan
Tifton Canada
Georgia
J. Charles Eldridge
Orvin C. Burnside Wake Forest University School of Medicine
University of Minnesota (Professor Emeritus) Winston-Salem
Minneapolis North Carolina
Minnesota
Clyde L. Elmore
Gerald A. Carlson Weed Science Extension Specialist (Retired)
North Carolina State University (Professor Emeritus) University of California
Raleigh Davis
North Carolina California
iix List fo srotubirtnoC
Richard S. Fawcett William C. Koskinen
Fawcett Consulting USDA, Agricultural Research Service
Huxley Soil and Water Management Research Unit
Iowa .tS Paul
Minnesota
Leonard .P Gianessi
CropLife Foundation David A. Laird
USDA, Agricultural Research Service
Washington, DC
National Soil Tilth Laboratory
Ames
Thomas J. Gould
Iowa
Bayer CropScience
Stilwell
Arthur H. Lange
Kansas
Former Weed Science Extension Specialist
University of California
Dennis S. Hackett Parlier
Syngenta Crop Protection, Inc. California
Greensboro
North Carolina Homer M. LeBaron
Agricultural Consultant
Nina E. Heard Heber
Syngenta Crop Protection, Inc. Utah
Greensboro
North Carolina Raphi .T Mandelbaum
LDD Technologies
Petach Tiqva
John E Hebblethwaite
Israel
Formerly of the Conservation Technology
Information Center
Kendra M. Marut
West Lafayette
En-Fate, LLC.
Indiana
Plymouth
Minnesota
Walter Heri (deceased)
Formerly of Ciba-Geigy Corp.
Janis E. McFarland
Basel
Syngenta Crop Protection, Inc.
Switzerland
Greensboro
North Carolina
Eugene R. Hill
Agricultural Biologist
Marshal D. McGlamery
Greensboro
University of Illinois (Professor Emeritus)
North Carolina
Urbana
Illinois
Robert A. Kahrs
Agricultural Consultant and Chemist Richard A. McLaughlin
Greensboro North Carolina State University
North Carolina Raleigh
North Carolina
Steven .T Kelly
The Scotts Company Gustav Miiller
Apopka Basel
Florida Switzerland
Ellery L. Knake James B. Nabors
University of Illinois (Professor Emeritus) Agricultural Chemistry Consultant
Urbana Greensboro
Illinois North Carolina
tsiL fo srotubirtnoC iiix
Michael Newton Shiv D. Sharma
Oregon State University University of Florida-WAS
Corvallis Citrus Research and Education Center
Oregon Lake Alfred
Florida
Charles A. Norwood
Kansas State University Amit Shukla
Garden City University of Saskatchewan
Kansas Saskatoon
Saskatchewan
James H. Orson Canada
The Arable Group
Morley
Robert L. Sielken .rJ
Norwich
Sielken and Associates Consulting, Inc.
UK Bryan
Texas
Thomas Parshley
Syngenta Crop Protection, Inc.
Bruce J. Simoneaux
Greensboro
Agricultural Consultant
North Carolina
Greensboro
North Carolina
Frank Pfister
Basel
Megh Singh
Switzerland
University of Florida-IFAS
Citrus Research and Education Center
David R. Pike
Lake Alfred
Agricultural Consultant
Florida
Champaign
Illinois
Dudley .T Smith
Texas A&M University
David L. Regehr
College Station
Kansas State University
Texas
Manhattan
Kansas
Keith R. Solomon
Centre for Toxicology and Department of
Edward .P Richard .rJ
Environmental Biology
Sugarcane Research Unit
USDA-ARS University of Guelph
Guelph, Ontario
Houma
Canada
Louisiana
Michael J. Sadowsky Carol N. Somody
University of Minnesota Syngenta Crop Protection, Inc.
St Paul Greensboro
Minnesota North Carolina
Lance .T Santo James .T Stevens
Hawaii Agricultural Research Center Wake Forest School of Medicine
Aiea Winston-Salem
Hawaii North Carolina
Elisabeth A. Scribner Darrell D. Sumner
US Geological Survey Wake Forest School of Medicine
Lawrence Winston-Salem
Kansas North Carolina
vix List fo srotubirtnoC
Arpad Z. Szarka Lawrence .P Wackett
Syngenta Crop Protection, Inc. University of Minnesota
Greensboro St Paul
North Carolina Minnesota
James M. Taylor Christoph Werner
Mississippi State University BASF Aktiengesellschaft
Mississippi State Product Safety, Regulations, Toxicology and Ecology
Mississippi GUP/CP-Z 470 und Li 556, D-67056
Ludwigshafen
E. Michael Thurman
Germany
SU Geological Survey
Lawrence
Lawrence .T Wetzel (deceased)
Kansas
Novartis Crop Protection, Inc.
Greensboro
Dennis .P Tierney
North Carolina
Syngenta Crop Protection, Inc.
Greensboro
Jere White
North Carolina
Kansas Corn Growers Association and Kansas Grain
Sorghum Producers Association
Achim Trebst
Garnett
Plant Biochemistry
Kansas
Ruhr University
Bochum
Robert A. Yokley
Germany
Syngenta Crop Protection, Inc.
Greensboro
Ciriaco Valdez-Flores
North Carolina
Sielken and Associates Consulting, Inc.
Bryan
saxeT
Chapter 2
History of the Discovery and Development of
Triazine Herbicides
Gustav MUller
Basel, Switzerland
Summary
The initial discovery and development of triazine herbicides took place between the years 1950 and 1970. During
that period, a group of leading scientists and agricultural experts of the former chemical company J.R. Geigy, Ltd.,
developed an idea for a new family of herbicides that would support modem agriculture. A small team of Geigy
chemists, biologists, and agronomists made excellent progress in turning that initial concept into not only new com-
pounds, but a new field of weed control research.
Geigy's principal scientist for chemical synthesis, Dr. Enrico Kntisli, started modifying existing chemicals known
to have an effect on plants, utilizing new molecular concepts that might be more successful in controlling weeds.
Kntisli altered a triazine ring with new active groups and discovered a tremendous source for new compounds with
herbicidal properties: the 4,6-dialkylamino-s-triazines. Within a short time period, researchers were able to select the
most active compounds with respect to both weed control activity and selectivity for corn and other crops. The limits
of substitution were soon defined, and work initially concentrated on the use of the unique compounds simazine and
atrazine on weed control in corn.
The Geigy scientists developed several new research methods in the areas of biological evaluation of weed con-
trol and crop tolerance. They also developed new science methodologies to investigate areas of toxicology, mode of
action, and dissipation in soils and plants.
The discovery and development of triazine herbicides were important scientific achievements and a significant
example of cooperation among chemists, biologists, and agronomists from around the world. Development of the tri-
azines led to unprecedented success in crop weed management.
Introduction
The triazine herbicides were discovered in the laboratories of J.R. Geigy, Ltd., an international chemical com-
pany founded in 1758 and based in Basel, Switzerland. A careful evaluation of the needs in agriculture inspired
two researchers in Geigy's Agrochemical Division to focus on discoveries important for weed control. In autumn
1950, Dr. George R. Ferguson, then head of the Technical Department of Geigy Agrochemical Division in the United
States, developed ideas on how agrochemical research could be diversified to meet new food production and agri-
cultural challenges. These ideas attracted the attention and support of Dr. Hans Gysin, a chemist and group leader of
an organic synthetic research team and later head of Geigy's Basel Agrochemical Research Department. Dr. Gysin
worked in the United States during the summer of 1951 to understand the weed control challenges farmers faced and
to explore future research in the field of agrochemicals to meet those needs.
For Geigy, the beginning of the herbicide project in 1952 was an ambitious venture in a new field of research.
Dr. Albert Gast was given the responsibility for biological evaluation of the herbicides, and .rD Enrico Kntisli, who had
joined the company in 1952, was responsible for the systematic synthesis of potential new herbicides. A good descrip-
tion and source of elucidating information on this early period was presented and published by Kntisli at an American
Chemical Society (ACS) Symposium in 1977. A part of this firsthand information is reported in extenso below.
How young an art was chemical weed control thent For a long time man had evidently not felt himself so help-
less against weeds as against other pests. It is not by chance that neither thorns nor thistles but mosquitoes, gadflies
31
41 History of the Discovery dna Development of Triazine Herbicides
and grasshoppers figure in the range of the ten biblical plagues. Pyrethrum, nicotine, copper, sulfur were chemical
control measures long before chemistry entered the field of weed control. In the late thirties, chemistry- and organic
chemistry in particular- made a decisive follow-up in the field of insecticides and fungicides, while the field of her-
bicides was in its infancy.
In the mid-fifties the range of practically-used organic herbicides was dominated by phenoxyacetic acids; in this
country (USA) the production of 2,4-D had reached an output of 34,000,000 pounds with a sales value of 28x 601
$ out of a total herbicide market of 38x 601 $ and out of a total pesticide market of 260x 601 .$ The range offered
to interested herbicide users included, in 1951, besides 2,4-D the O-alkyldinitrophenols, pentachlorophenol, trichlo-
roacetic acid, sodium isopropylxanthate, additional chlorophenoxyacetic acids, isopropyl-N-phenylcarbamate,
endothal, maleic acid hydrazide and p-chlorophenyldimethylurea. The concept of a preemergence treatment of weeds
had just been inaugurated by the last-mentioned compound.
Herbicides, 1951
X
D-4,2
CI-'~OCH2--COOH T-5,4,2
APCM
Y
IC ~ aN3OSO2HC--2HCO ,etafluslyhteyxonehporolhciD-4,2 aN tlas
I
IC
~~
7- H3CiOOCHN lyporposI etamabraclynehp-N
~
HOOC cilahthpordyhoxodnE-6,3 dica
LAHTODNE
HOOC
0
HN enonizadiryp-)H2(-3-yxordyH-6
HM
HO
k~~ 3HC
(-3 -)lyne4 hporolhC-' 1,1 id- lyhtem aeru
CI NOCHN \ UMC
HC 3
This was the status when we commenced, in 1952, a project for the discovery and the development of herbicides and
defoliants. The decision to initiate such a project was taken by the management of our company, then J.R. GEIGY
Ltd., a year earlier. The company had at that time experience in the field of pharmaceuticals, dyestuffs, insecticides,
moth-proofing agents, and fungicides. It is a pleasure, and an expression of gratitude, for me to recall that .rD Hans
Gysin was the inspiring and enthusing leader of the project and that .rD Albert Gast cared, with high expertise, for
a major part of the greenhouse and field evaluation. How did we attack the problem? In the conventional way: by
establishing work hypotheses, by synthesizing, by screening, by discarding many compounds.
Introduction 51
3HO/
HNHNOC2HC 2
CIC>NHSO2N
I
HNHNOC2HC 2
HC\ 3
46252-G 09452-G
C > 3HC
/
IC ~' )5H2C> (NOCOCHN 2 IC N2OSO \
HC 3
47352-G 19452-G
_~ > 3HC
/
IC ~' 2)5H2> C(NOCOCO
IC __ HCOOCHN2OS \ 3HC
77352-G 49452-G
IC C > 2)3HC(NOCHC=HC
68452-G 59752-G
In a first round, we tried to obtain, through structural variation of known active molecules, new and superior
biological effects. eW were particularly interested to check the consequences of the isosteric replacement of struc-
tural elements in chlorophenyl derivatives as shown above. In the greenhouse, during biological evaluation G-25486
showed defoliant properties which led to structural variation work. However, no compound useful under practical
conditions could be found. G-25795 demonstrated remarkable root-promoting activity so that many further ana-
logues and homologues were synthesized.
H 5
N N 89752-G
>-NHJ -OC H,
N
--/
IC
N N 20972-G
c, '
IC
40852-G
N N
N2)5H2C( s -LL-,./ 2)5H2C(N
N
IG
41852-G
N N
05H2C ~ -LL// 5H2CO
N