Peroxidizing Herbicides

Experts in herbicide research and development - chemists and plant physiologists -, have written 15 chapters that review all aspects pertinent to peroxidizing herbicides, compounds of topical interest since extremely low use rates ensure high environmental safety. Topics covered include structure-activity relationships, relevant patent literature, preparative methods, modes of action, greenhouse screening, laboratory assays, plant pigment biochemistry, and enzymology of the decisive target enzyme of this class of herbicides. This comprehensive review will be welcomed as a unique and timely compilation of the current status of peroxidizing herbicide research and development. It will be of interest to professional chemists and biologists in agrochemical companies, universities and agricultural colleges.

Developments in the understanding of herbicide activity and toxicology have expanded tremendously in the past fifteen years. Research on the mechanism of action of most major classes of herbicide chemistry has provided scientists with excellent insight into enzyme targets. More recently, developments in molecular biology have provided information about herbicide action at the genetic level. Less well understood are the toxicological aspects of herbicide activity that culminate in plant injury or death. Toxicology, Biochemistry and Molecular Biology of Herbicide Activity is a review of the recent literature on most of the major classes of herbicide chemistry in commercial use. The chapters include information about different aspects of herbicide activity related to photosynthesis, inhibition of amino acid biosynthesis, disruption of cell division and microtubule assembly, activity of phytohormone (auxin) mimics, inhibition of fatty acid biosynthesis and some developments in the understanding of herbicide resistance.

Target Assays for Modern Herbicides and Related Phytotoxic Compounds is a laboratory guide that features 38 comprehensive contributions to determine and quantitate the inhibition activity of modern herbicides and related phytotoxic compounds at their targets. Using algal or higher-plant model species as well as cell-free enzymatic systems, assays are described for use with modern equipment typically found in a biochemical laboratory. Many details of the tests described in this volume are being published for the first time. Assays discussed include carotenoid and chlorophyll biosynthesis and degradation, photosynthetic electron transport, amino acid biosynthesis, fatty acid formation, and cell division. Some model systems and related topics are also described. Each chapter represents an easy-to-read recipe with minimal theory including some key references for further reading. Original data from the experiments are provided, and most of the notable laboratories around the world are represented. Target Assays for Modern Herbicides and Related Phytotoxic Compounds features updated methodology and procedures that will be a tremendous asset to plant biochemists; agriculture, plant protection, and weed control experts; agrochemical herbicide specialists in industry and government; and students in agricultural biochemistry and physiology.

This book is divided into two sections namely: synthesis and properties of herbicides and herbicidal control of weeds. Chapters 1 to 11 deal with the study of different synthetic pathways of certain herbicides and the physical and chemical properties of other synthesized herbicides. The other 14 chapters (12-25) discussed the different methods by which each herbicide controls specific weed population. The overall purpose of the book, is to show properties and characterization of herbicides, the physical and chemical properties of selected types of herbicides, and the influence of certain herbicides on soil physical and chemical properties on microflora. In addition, an evaluation of the degree of contamination of either soils and/or crops by herbicides is discussed alongside an investigation into the performance and photochemistry of herbicides and the fate of excess herbicides in soils and field crops.

Chemical pest control is in use in practically every country in the world since agrochemicals play a decisive role in ensuring food supply and protection against damage by pests, insects and pathogenic fungi. Particularly in the half century since World War II, food production has risen dramatically in most parts of the world. In the last 20 years, the yield of major crops has roughly doubled in Western agriculture and there is still the potential for further achievements, particularly in the developing countries. The world's cereal and rice production, now more than 2 billion tons/year, has to increase by 2. 4% annually to cope with the rising food demand caused mainly by the growing population and improvement of living standards in most of the developing countries. Such a demand for food has to be achieved by higher yields from the restricted arable land already in use. Global farm land resources are about 1. 4 billion ha, of which 1. 2 billion ha is cultivated with major crops. Experts agree that a future substantial addition of new produc tive areas is unlikely. Those with a high yield potential are already in use; new fields with a lower output may possibly be obtained by cultivation of arid or cold areas. More recently, new areas of large-scale farmland have been devel oped in tropical regions of Latin America, primarily in Argentina and Brazil, at the cost of the destruction of tropical rain forest.

Since the middle of the Sixties, new types of formulation for biologically active com pounds have been developed, which have been introduced into the literature under the term Controlled Release Formulations (CRF). Stimulated by results from former and successful pharmaceutical research, which was engaged in the production of prepa rations with protracted effects (introduction onto the market in the year 1952 of D amphetamine in the form of pellets, coated to varying degrees with fats and waxes) 1), experiments were carried out to transfer the prolongation of effectiveness to pesticidal substances also, by means of a depot formulation. Initial work was concerned with the production of protective coatings for sonar systems in marine ecosystems. By means of antifouling paints or rubber coatings containing tri-n-butyl-tin oxide (TBTO), the growth of marine organisms on sonar domes, buoys and hulls in the water could be effectively prevented 2. 3). Controlled release formUlations of pesticides are defined as depot systems which continuously release their toxic constituents into the environment over a specified period of time (usually months to years) 4). According to this definition, such formu lations can be successfully employed where a chronic exposure to biologically active compounds is required over a longer period. The following hypothetical example is intended to illustrate this 5). In Fig. 1, the duration of activity of a non-persistent pesticide with a loss rate under environmental conditions of t1/2 = 15 days, is graphically illustrated.

In recent decades, repeated use of herbicides in the same field has imposed selection for resistance in species that were formerly susceptible. On the other hand, considerable research in the private and public sectors has been directed towards introducing herbicide tolerance into susceptible crop species. The evolution of herbicide resistance, understanding its mechanisms, characterisation of resistant weed biotypes, development of herbicide-tolerant crops and management of resistant weeds are described throughout the 36 chapters of this book. It has been written by leading researchers based on the contributions made at the International Symposium on Weed and Crop Resistance to Herbicides held at Córdoba, Spain. This book will be a good reference source for research scientists and advanced students.