bluuebunny/crossref_metadata_2025 huggingface dataset:
Fertilizers
Authors: Taylor Alan W.
Published: November 2003

The function of fertilizer applications is to raise the level of soil fertility and biological activity in the soils and farming areas where they are used by increasing the amounts of available plant nutrients, in particular, nitrogen and phosphorus. As a result, adverse environmental impacts may occur to water quality. In recent years, there has been a large body of research directed toward the need to reduce the fertilizer contribution to these problems.
Fugacity Modeling
Authors: Cahill Thomas M. , Mackay Donald
Published: November 2003

The environmental fate of applied agrochemicals can be estimated with either conventional concentration‐based or fugacity models. Although both types of models can predict the fate of chemicals, the fugacity models have several inherent advantages. Fugacity models express the chemical potential in diverse media in common units of pressure, and so the chemical equilibrium among media is expressed directly. This is particularly valuable when assessing the migration of the chemical among diverse media such as air, water, soil solids, plants, and animals. Chemical transport and transformation processes, such as advection, diffusion, and reaction, are quantified using
D
‐values, which share identical units despite describing very different processes. This uniformity aids in identifying the important processes governing chemical fate in the environment, and it simplifies the formulation and interpretation of the modeling equations. Modeling and assessing the fate of agrochemicals in terms of fugacity as well as concentrations can contribute to a fuller understanding of agrochemical behavior. This article presents a brief conceptual overview of the fugacity framework, describes situations using malathion as an example, and provides references for further consultations.
Fungicides, 2‐Aminopyrimidines
Authors: Hollomon Derek W.
Published: November 2003

2‐aminopyrimidines are a group of three systemic fungicides active only against powdery mildews (
Erysiphales
). Introduced over 30 years ago, only ethirimol and bupirimate are used today as a seed treatment and spray, respectively. They have a low toxicity to mammals and other animals, but bupirimate is harmful to some aquatic organisms. Their half‐life, especially in sandy soils, is less than 6 months. 2‐aminopyrimidines stop mildew infection at the appressorial stage, although they do affect later stages of mildew development. They target adenosine deaminase (EC 3.5.4.4), an enzyme involved in purine salvage. Resistance developed rapidly in several powdery mildews to both ethirimol and dimethirimol, but the mechanism of resistance remains unclear.
Fungicides, Aromatic Hydrocarbons
Authors: Lyr H.
Published: November 2003

Aromatic hydrocarbon fungicides represent an older and chemically heterogeneous group of fungicides consisting of an aromatic ring system. They have been in use for a long time, but have lost their importance. Some of them are still valuable compounds in tropical countries and in use for controlling storage diseases. Many of them could be replaced by newer compounds with a broader antifungal spectrum, better physical properties, and higher activity.
Fungicides, Carbamates
Authors: Buschhaus H.
Published: November 2003

Prothiocarb [N‐(3‐dimethylaminopropyl)thiolcarbamate hydrochloride] was first described in 1975 as a fungicide for control of soil‐borne
Pythium
spp. and
Phytophthora
spp. The marketing of this compound was stopped in 1978, and a close analogue, propamocarb hydrochloride [propyl 3(dimethylamino)propylcarbamate hydrochloride] was introduced in 1979. Propamocarb hydrochloride is a versatile, effective, and safe carbamate fungicide with specific activity against numerous
Oomycete
species, causing seed, seedling, root, foot, and stem rots and foliar diseases in numerous edible crops and ornamental plants. Propamocarb hydrochloride was discovered and developed by Shering AG. The mode of action is different from that of other
Oomycete
fungicides, and propamocarb hydrochloride effectively controls strains that have developed resistance to other fungicides. A full data package is available for propamocarb, but that for prothiocarb is incomplete.
Fungicides, Copper Compounds and Sulfur
Authors: Tweedy B. G.
Published: November 2003

Copper compounds and elemental sulfur are the two oldest of the agricultural chemicals used to control pests. Elemental sulfur and crude mixture of lime and sulfur became important for the control of powdery mildews of tree fruits, grapes and hops, and peach leaf curl. Factors that have prolonged the life of these products are low cost, lack of resistance, and safety to humans and the environment. Copper also continues to be an important tool for controlling diseases, and it continued use is attributed to safety and low cost when compared with the organic fungicides. Except for copper and sulfur, inorganic chemistry has not had an important role in controlling plant disease.
Fungicides, Dicarboximides
Authors: Leroux Pierre
Published: November 2003

The dicarboximide fungicides are in fact cyclic imides substituted on the nitrogen atom by a 3,5‐dichlorophenyl group. They can be used against various Ascomycetes (e.g.,
Alternaria
,
Botrytis
,
Monilinia
,
Sclerotinia
) and Basidiomycetes (e.g.,
Rhizoctonia
). Under field conditions, their activity against fungal pathogens is mainly preventive. Their target site could be a histidine protein kinase–involved fungal osmoregulation. In field strains and laboratory mutants of
Botrytis cinerea
, dicarboximide resistance seems to be determined by mutations in the gene encoding this kinase. The metabolism of these dicarboximides generally involves the cleavage of the cyclic imide.
Fungicides, Dimethomorph
Authors: Ypema Hendrik
Published: November 2003

Dimethomorph was discovered in 1983 by Shell Research as a result of optimization and screening of several cinnamic acid derivatives with fungicidal activity against the genus
Phytophthora
. The primary binding site of the molecule is unknown. In the presence of dimethomorph, the biochemical processes involved in normal cell wall biogenesis of sensitive Oomycete fungi are impacted, which may result in cell lysis. Dimethomorph was subsequently marketed by Shell, American Cyanamid, and BASF for control of downy mildew and
Phytophthora
diseases in vines, potatoes, vegetables, and other crops. It is used in combination or in mixture with contact fungicides.
Fungicides: Ferimzone
Authors: Ypema Hendrik
Published: November 2003

Ferimzone was introduced by Takeda Chemical Industries Ltd. Ferimzone has systemic properties. It is mainly used in rice‐producing areas in Asia for the control of brown spot (
Helminthosporium oryzae
), narrow brown leaf spot or Cercospora leaf spot (
Cercospora oryzae
), and rice blast (
Pyricularia oryzae
). It is also marketed as a mixture with phthalide or tricyclazole. The mode of action of ferimzone in target fungi is unknown, however, research to date suggests that the compound may affect membrane function.
Fungicides, Fungal Resistance to Chemical Controls
Authors: Hollomon Derek
Published: November 2003

The long‐term viability of pesticides to control pests, diseases, and weeds is always threatened by resistance. Consequently, there is a need to understand the causes of resistance and the factors that influence its spread, so that the problem can be managed effectively. Chemical pesticides bind to specific sites in their target proteins, and small changes can disrupt this binding. High levels of resistance are often conferred by just a single amino acid change, and the same change causes resistance to a pesticide group in different species, and even phyla. Surprisingly, these changes are generally in highly conserved regions of the target protein. Other mechanisms, such as detoxification, increased efflux associated with multidrug resistance (MDR), overexpression of the target protein and altered metabolic pathways all contribute to resistance, but generally these mechanisms confer lower levels of resistance than target site changes.

Biochemistry provides ways to generate resistance, but individuals possessing these mechanisms must not suffer fitness penalties as a consequence. Bioassay remains the main way to monitor resistance, although it is often resource intensive, and it provides little information on the mechanism conferring resistance. Biochemical and DNA methods offer ways to overcome these difficulties, and they are increasingly used to monitor resistance where mechanisms are known.

Combining all this information allows assessment of resistance risk and implementation of strategies to manage the problem. Predictive modeling can be useful, but there is always an empirical component in developing anti‐resistance strategies. A corner stone of all anti‐resistance strategies involves using pesticides with different modes of action, and integrating this with nonchemical control measures. Examples of successful anti‐resistance strategies are few, and effective control often rests with the development of new pesticides with novel modes of action.
Chemical Activators of Disease Resistance
Authors: Staub Theodor , Kunz Walter , Oostendorp Michael
Published: November 2003

Chemical activation of disease resistance in plants represents an additional option for growers to protect their crops from losses due to plant diseases. Against some pathogens, like bacteria and viruses, resistance activators may be the best chemical option where genetic resistance is not available or not sufficient. Against dynamic fungal pathogens with a history of adaptation to fungicides or to resistant cultivars, the integration of chemical activators of broad‐spectrum plant defenses with genetic resistance and fungicides is likely to prevent or slow such pathogen shifts. The challenge is to integrate optimally on each crop the new chemical activators of broad‐spectrum plant defense with all other disease control and crop production methods to achieve more sustainable crop health management systems.
Fungicides, Melanin Biosynthesis Inhibitors
Authors: Motoyama Takayuki , Yamaguchi Isamu
Published: November 2003

Tricyclazole, pyroquilon, phthalide, and carpropamid are melanin biosynthesis inhibitors (MBIs) that are used as fungicides for the control of the rice blast disease. The primary targets of these chemicals are enzyme(s) in the biosynthesis pathway of a fungal melanin, the dihydroxynaphthalene (DHN) melanin. DHN melanin is a black pigment synthesized through the pentaketide pathway that includes fusion of five isoprenyl units, two sets of alternating reduction and dehydration steps, and polymerization of 1, 8‐dihydroxynaphthalene. Tricyclazole, pyroquilon, and phthalide inhibit the reduction step(s), and carpropamid inhibits the dehydration steps. MBIs inhibit the rice blast disease without fungicidal activity. This selective activity of MBIs may offer advantages over conventional fungi toxic chemicals which act on biochemical processes common to many nontarget organisms in the environment. We describe the following information of the four MBIs; nomenclature, physical properties, agricultural uses, mode of action, metabolism and environmental fate, toxicology and safety aspects. To explain the superior features of MBIs, we provide the detailed mode of action of these chemicals.
Fungicides, Multisite Inhibitors—Broad Spectrum Surface Protectants
Authors: Uesugi Yasuhiko
Published: November 2003

Chemicals first used in agriculture to control pant diseases were inorganic fungicides such as elemental sulfur, lime sulfur, and copper fungicides, including Bordeaux mixture. Those fungicides are primarily applied to cover the surface of the plants to protect them from various plant pathogens. They are, therefore, broad‐spectrum surface protectants and have been used since the nineteenth century. However, their use has been limited because of their lower level of effectiveness, risk of their toxicity to the plants, and lack of compatibility in use with other fungicides and insecticides.
Fungicides, Organophosphorus Compounds
Authors: Sasaki Mitsuru
Published: November 2003

Physicochemical property, biological activity, mode of action, agricultural uses, chemistry, metabolism and environmental fate, and toxicity and safety aspects of organophosphorus fungicides, including edifenphos, fosetyl‐aluminium, iprobenfos, pyrazophos, and tolclofos‐methyl, are described.
Fungicides, Phenylamides/Acycalanines
Authors: Gisi Ulrich , Ziegler Hugo
Published: November 2003

Phenylamide fungicides such as metalaxyl, mefenoxam (metalaxyl‐M), furalaxyl, benalaxyl, ofurace, and oxadixyl are antifungal compounds that specifically control plant pathogens of the oomycetes, including downy mildews and blights. They inhibit rRNA synthesis and can control pathogens during preventive, curative, and eradicative phases of the disease cycle, mainly due to their systemic (acropetal) translocation in crop plants. Phenylamide fungicides are combined in mixtures with compounds of other chemical classes in order to enlarge the spectrum of activity, enhance the overall efficacy, and prevent and delay the development of resistant subpopulations.
Fungicides, Soil Fumigants
Authors: Sims James J.
Published: November 2003

The mandated elimination of methyl bromide as a soil fumigant because of its ozone‐depleting chemistry is scheduled to be complete by 2005. Chemicals in current use as soil fumigants and some promising new chemicals are reviewed. The compounds are listed with their important chemical and physical properties.
Fungicides, Tubulin‐Binding Compounds
Authors: Ishii Hideo
Published: November 2003

In the late 1960s, the systemic fungicides benzimidazoles and thiophanates, which are transformed to benzimidazoles, were first commercialized. Since then, this group of fungicides has been widely used worldwide for controlling a number diseases on various crops. Benzimidazole fungicides have been shown to bind the β‐subunit of tubulin, a protein essential for eukaryotes, and result in interference with nuclear division in the fungus. Although resistance development of the targeted pathogens often occurs, tubulin‐binding compounds still look attractive as agricultural fungicides and a novel compound, zoxamide, has further been developed recently.
Fungicides, Hymexazol
Authors: Ypema Hendrik
Published: November 2003

Hymexazol was originally introduced by Sankyo. Common names used for this fungicide are hymexazol and hydroxyisoxazole. The fungicide is marketed under the tradename Tachigaren. Hymexazol is distinct from most fungicides with activity against Oomycete fungi in that it is active against certain
Aphanomyces
spp. Hymexazol is used worldwide as a systemic soil and seed fungicide for the control of diseases caused by
Fusarium
,
Aphanomyces
,
Pythium
, and
Corticium
spp. in rice, sugarbeet, fodderbeet, vegetables, cucurbits, and ornamentals.

Investigations into its mode of action suggested that hymexazol may interfere with fungal RNA and DNA syntheses. Hymexazol is rapidly translocated and has locally systemic distribution properties. Upon entry into the plant, hymexazol is rapidly transformed into glucosides. The O‐glucoside has fungitoxic activity, whereas the N‐glucoside has been associated with certain plant growth promoting effects, such as stimulation of lateral root hair development in seedlings.
Genetic Toxicity and Cancer from Agrochemicals
Authors: Gammon Derek W. , Frank Joseph P.
Published: November 2003

Agrochemicals are regulated very thoroughly at both the national and international levels. Toxicology tests generally include lifetime rodent studies to determine whether or not the the compound is capable of causing cancer. In addition, a battery of shorter duration tests designed to evaluate an agent's genotoxic potential are conducted. These studies provide insight into the toxicological mechanisms of the agents tested and provide an opportunity to evaluate the relationship between activity at the molecular level and observations made in cancer studies. In this article, the major tests required by regulatory authorities have been described and the results obtained for many agrochemicals are presented. The main databases used were IARC, USEPA and CDPR and the main publications considered were Eastmond and Balakrishnan (2001), Gold and Ames (2001), and Sasakiet al.(2000). Tumor sites are also presented and correlations drawn, where possible, between genotoxic activity and reported oncogenicity. Furthermore, a number of types of cancer are described where the primary cause may not be a genotoxic event, but instead an epigenetic phenomenon, and some possible examples are given. Finally, some suggestions are provided for potentially improving the regulation of pesticides that cause cancer using the tools of molecular biology.
Glyphosate
Authors: Duke Stephen O. , Baerson Scott R. , Rimando Agnes M.
Published: November 2003

Glyphosate is the most widely used, biggest selling, and fastest growing herbicide in the world. The herbicidal properties of glyphosate were disvocered by Monsanto Agricultural Products Company in 1970, and it was first marketed by Monsanto in 1974. Since then, its use has continually increased, especially since the introduction of glyphosate‐resistant crops and the expiration of the glyphosate patent. Glyphosate is unique in chemical structure and molecular target site, and its unparalleled success has led many to consider it the most “ideal” herbicide available.
Herbicides, Biotechnology for Control of Weeds
Authors: Duke Stephen O. , Scheffler Brian E. , Boyette Douglas , Lydon John , Oliva Anna
Published: November 2003

Biotechnology can be used to enhance the management weeds in several ways. Crops have been made resistant to herbicides by inserting transgenes that impart herbicide resistance into the plant genome. Glyphosate‐, glufosinate‐, and bromoxynil‐resistant crops are commercialized in North America. This technology has been highly successful, transforming weed management in several major crops. Selection for mutations that impart herbicide resistance to crops has also been successfully used to generate herbicide‐resistant crops. There are several living microbial products for the biocontrol of weeds. These agents have not been very successful, but work is being conducted to improve them with biotechnology methods. The use of crops that produce their own herbicides (allelopathy) has been even less successful. Biotechnological approaches are being used to generate crops that can poison weeds with less or without synthetic chemical inputs. Research on natural phytotoxins from plants (allelochemicals) has also provided lead compounds for herbicide discovery.
Herbicides, Cinmethylin
Authors: Dayan Franck E. , Romagni Joanne G. , Duke Stephen O.
Published: November 2003

Cinmethylin was developed by Shell Chemical Company in the early 1980s as a weed control agent for monocotyledonous species. This herbicide controls important grasses, such as green foxtail and barnyardgrass and suppresses the growth of several broadleaf weeds such as prickly sida and velvetleaf. The mode of action of cinmethylin eluded scientists for many years in spite of several efforts by industrial and government research groups. This article will review the development of cinmethylin and its primary use in agriculture, the work that led to the discovery of its mode of action, and the function of the enzyme targeted by this herbicide.
Herbicides, Inhibitors of Photosynthesis at PhotosystemII
Authors: Oettmeier Walter
Published: November 2003

Herbicides of photosystem II inhibit the reduction of plastoquinone at the secondary quinone acceptor site (QB‐site) and its subsequent reoxidation at the cytochromeb6/f‐complex. TheQB‐site is located at the photosystem II reaction center protein called D1. When the reduction of plastoquinone is blocked by the herbicide, light‐induced charge separation leads to recombination processes that via a chlorophyll triplet state generate reactive oxygen species. These will cause extensive damage in photosystem II and eventually kill the plant. Amino acids involved in herbicide binding can be identified in three ways: 1) by comparison with the well‐known X‐ray structure of the bacterial photosynthetic reaction center, 2) by photoaffinity labeling with photolabile radioactive analogs of herbicides, and 3) by analysis of the herbicide binding in herbicide‐resistant mutants of plants, algae, and cyanobacteria with known mutations in the D1 protein. Herbicides of photosystem II belong to the following chemical classes:s‐triazines, triazinones, uracils, ureas, phenylcarbamates, anilides, cyanophenols, dinitrophenols, and some chemicals that do not belong to these classes, like bentazon, fluoromidine, pyrazon, and pyridate.
Turfgrass Pesticides: Management and Environmental Issues
Authors: Clark J. Marshall
Published: November 2003

The lawn and turf industry in the United States, including private and commercial lawn care, generates approximately $25 billion annually. The United States golf industry generates approximately $64 billion. A variety of pests are capable of damaging turf, and a number of fungicide, insecticide, nematicide, and herbicide products, respectively, are applied to promote turf health. Currently, pesticide application is the major control factor in lawn and turf management.
Insecticides, Imidacloprid
Authors: Kagabu Shinzo
Published: November 2003

In 1986, imidacloprid was discovered as a new insecticide with a unique structure and with a hitherto unrecognized insecticidal performance. Since being launched on the Japanese market in 1992, its sales potential has increased yearly, and it ranks as one of the top‐selling insecticides in the world in 2000. Imidacloprid, besides its agricultural use, is also used for the control of subterranean pests and pet ectoparasites.
Immunoassays
Authors: Wang Shuo , Kennedy Ivan R. , Skerritt John H.
Published: November 2003

The development and application of specific immunoassays is reviewed, as a complementary method to instrumental methods such as gas–liquid chromatography or high‐performance liquid chromatography. The simplicity of performing immunoassay methods, and their high detection sensitivity is traded off by the greater effort required for method development. In some (but not all) cases, immunoassay methods may be lower in precision than instrumental methods, but higher sample throughput may allow more analysis of a larger number of subsamples. The review describes the steps in the development of immunoassays for agrochemicals (including design and synthesis of haptens, conjugation to carrier proteins and enzymes, antibody production and immunoassay formats), application of immunoassays to a wide range of agrochemicals and immunoassay validation. The application of assays to food and environmental sample matrices and the need to overcome sample matrix interference is reviewed.
Inhalation Toxicity
Authors: Pauluhn Juergen
Published: November 2003

Several animal models have traditionally been used in inhalation studies with pesticides. Especially in inhalation toxicity, the introduction of new animal models is usually a very slow and involved process, as respective baseline data are not yet available and, due to the number of variables involved, the validation of novel exposure systems or new animal models is commonly more elaborate when compared with other routes. Moreover, experimental animals may experience exposure‐related stress and ensuing physiological response following inhalation to local irritants, which may be absent following other routes. Therefore, the selection of the most appropriate test animal model for an inhalation toxicity study is not a simple matter.
Herbicides, Carotenoid Biosynthesis Inhibitors
Authors: Dayan Franck E. , Duke Stephen O.
Published: November 2003

The carotenoid biosynthetic pathway is an important target site for several classes of herbicides. Carotenoid biosynthesis can be stopped by inhibiting a number of key enzymes. Phytoene desaturase (PDS) is the most common target site of herbicides affecting carotenoid production. As a group, these herbicides are considered environmentally safe because they are used at very low concentrations and target an enzyme not found in animals. As a result, fluridone is the most successful aquatic herbicide available to date.
Insect Resistance to Insecticides
Authors: Brown Thomas M.
Published: November 2003

Resistance to pesticides has evolved, not only in insects, but also in acarines, weeds, fungi, bacteria, rodents, and other pests. The phenomenon of resistance is due to Darwinian evolution at a rate that is accelerated by the intensity of selection from pesticides. Insects present many difficult challenges related to resistance in that they are especially well adapted for dispersal through flight, they have a high reproductive capacity with multiple generations per year, and they are often difficult to detect in products traded around the world, such as grain, flowers, or even used tires.
MALDI
Authors: Wilson M. F. , Startin J. R.
Published: November 2003

Matrix‐assisted laser desorption/ionization (MALDI) is a specialized sample introduction and ionization technique for mass spectrometry (MS). Following its announcement by Hillenkamp and Karas in 1988, MALDI was quickly recognized as a major new weapon in the armory of chemists and biochemists for measurement of the molecular weights of large molecules. MALDI has been most widely and most successfully applied to the study of proteins and peptides, but it has also proved useful for other types of biomolecules, for synthetic polymers, and to a lesser extent, for lower molecular weight compounds.
Metabolism of Herbicides
Authors: Hoagland Robert E. , Zablotowicz Robert M.
Published: November 2003

Herbicide metabolism in plants and microorganisms is a major factor in the dissipation of these compounds in the environment. Metabolic degradation of herbicides by plant enzymes is the main mechanism of plant resistance to such phytotoxic chemicals. Alternatively, some plant enzymes can metabolize certain nonphytotoxic chemicals (termed proherbicides) to yield active herbicides within the plant. Generally, metabolism of pesticides can be categorized into three separate phases: phase I (enzymatic conversion of a herbicide to a less active compound), phase II (enzymatic conjugation of the parent compound or metabolites generated from phase I), and phase III (conversion of phase II metabolites into secondary conjugates of bound residues). These categories are discussed generally and specifically using typical herbicides as examples. The metabolic divergences and similarities of plant and microbial metabolism are discussed in general, and selected compounds from various herbicide families are used to illustrate metabolic routes of herbicides in plants and microorganisms.
Microcosms
Authors: Edwards Clive
Published: November 2003

The maintenance of soil quality, fertility, and structure is essential to the long‐term health and biodiversity of terrestrial ecosystems. A major problem is that ecologists still have a relatively poor understanding of the ecology, structure, and functioning of soil ecosystems and the dynamic processes in soil that are driven by biological cycles and interactions. This makes the reliable assessment and prediction of the impact of pollutants on soil ecosystems very difficult. For instance, there is a gap between single‐species laboratory tests and field studies. Therefore, using microcosms and theoretical computer simulation models can bridge this considerable gap.
Minor Use Pesticides, Registration
Authors: Markle George M. , Baron Jerry J. , Holm Robert E.
Published: November 2003

The Interregional Research Project No. 4 (IR‐4 Project) was organized 37 years ago by the Directors of the State Agricultural Experiment Stations (SAES) to obtain regulatory clearances for crop protection chemicals on minor food crops when the economic incentives for the registrants precluded private sector investment. IR‐4 has been administered by the United States Department of Agriculture (USDA) and Cooperative State Research Education and Extension Service (CSREES) since its inception in 1963. The Agricultural Research Service (ARS) component of the USDA established a companion minor use program in 1976 to provide further program support. The objectives of the program were expanded in 1977 to include registration of pest control products for the protection of nursery, floral, forestry and turf crops and again in 1982 when the objective of clearance of biological control agents or biopesticides was added. Also in 1982, the project added a Minor Use Animal Drug component to the work effort. The animal drug portion of the program became a separate entity several years later and continues today as a separate project funded by CSREES. The minor crop program works as a model government funded program due to a unique partnership formed between the USDA (CSREES and ARS), the IR‐4 Headquarters and Regional Laboratory staff, the land grant university system, the crop protection industry, commodity and grower groups, the Environmental Protection Agency (EPA) and the California Department of Pesticide Regulation to bring crop protection solutions to minor crop growers.
Natural Enemies
Authors: Jepson Paul , Lewis Gavin B.
Published: November 2003

Terrestrial nontarget arthropods make a vital contribution to agroecosystems. Their functional roles include pollination of crop and noncrop plants, regulatory interactions maintaining pest species below economically damaging thresholds, contributing to the nutrient recycling process, and providing food to species higher up the food chain. Of particular interest in terms of assessing the risk of agrochemicals to the environment is the species group known as arthropod natural enemies. These are predators and parasitoids, which prey on other arthropods, thereby helping to limit the population increase of predominantly phytophagus species.
Natural Product Pesticides
Authors: Ujváry István
Published: November 2003

During their evolution, living organisms have developed a broad array of defense strategies often involving complex and dynamic chemistries that assure survival, coexistence, or in some cases, territorial dominance of the species and the individual. Since prehistoric times, people in all parts of the world have exploited natural products in one form or another in curing diseases and fighting pests that endanger their health or compete for their food. Natural products can be used either directly in pest control or can serve as models for the development of new synthetic analogs with favorable biological and physiochemical properties. Although natural products can affect several different organisms, they can be categorized according to their main use as follows: insect control agents; weed control agents, including plant growth regulators; disease control agents, including fungicides and bactericides; nematicides; and rodenticides.
Nematicides
Authors: Chitwood David J.
Published: November 2003

Few chemical nematicides remain registered for agronomic use because of the deregistration of many soil fumigants. The major chemical nematicides presently available include 1,3‐dichloropropene, metam sodium, methyl bromide, aldicarb, oxamyl, ethoprop, and fenamiphos. Most of these face additional future restrictions. Various formulations and application techniques are utilized in order to maximize nematicidal efficacy and minimize atmospheric or groundwater contamination. Although resistance of plant‐parasitic nematodes to chemical nematicides in agricultural fields is insignificant, in some cases, enhanced microbial degradation reduces nematicidal effectiveness. Two biopesticidal nematicides are registered in the United States: a chitinous material and a plant extract. Future control of phytoparasitic nematodes will involve increased use of nonchemical, sustainable, or site‐specific management tactics. Fumigants receiving increased research attention as methyl bromide alternatives include the registered sodium tetrathiocarbonate and the unregistered methyl iodide and propargyl bromide. In addition, phytochemicals and other biorational chemicals are providing leads for discovering future nematicides. Future implementation of safe and effective chemical nematode management will be challenging.
Nitrate in Groundwater
Authors: Addiscott Thomas
Published: November 2003

The nitrate ion is one of the ubiquitous chemical substances on the planet and is nearly always found in water. Most of the water around us contains nitrate, but the water with which we are concerned here is groundwater, which is water accumulated in the saturated zones of certain rock formations, usually at depth. Most of this water has passed through the soil before it accumulates, so that activities at the soil surface, particularly agriculture, can have a strong influence on the concentrations of nitrate and other agrochemicals in groundwater. Despite its commonplace nature, nitrate has for at least two decades been a source of widespread concern because of its perceived effects on our environment and our health.
Organophosphorus Insecticides
Authors: Eto Morifusa
Published: November 2003

Many organophosphorus (OP) insecticides including acaricides and nematicides are used in agriculture and public health all over the world; they are the largest insecticide group with some 38% of worldwide sales in 1996. Their variety in structure reflects the broad range of their physicochemical properties such as water solubility, lipophilicity, volatility, and persistency in the environment. Owing to this wide range of physicochemical properties, OP insecticides offer various degrees of activities in soil, in plants, in the vapor phase, and against a variety of pests, though they exhibit a single mode of action, i.e., acetylcholinesterase inhibition. In this entry, the description of general principles on the synthesis, chemical reactions, mode of action and toxicity, metabolism, and environmental fate is followed by that of individual OP insecticides, which involve 71 currently used chemicals. The names of discussed chemicals are as follows: acephate, azamethiphos, azinphos‐ethyl, azinphos‐methyl, cadusafos, chlorethoxyfos, chlorfenvinphos, chlormephos, chlorpyrifos, chlorpyrifos‐methyl, coumaphos, cyanophos, demeton‐
S
‐methyl, diazinon, dichlorvos, dicrotophos, dimethoate, dimethylvinphos, disulfoton, EPN, ethion, ethoprophos, etrimfos, famphur, fenamiphos, fenitrothion, fenthion, flupyrazofos, fonofos, formothion, fosthiazate, heptenophos, isazofos, isofenphos, isoxathion, malathion, mecarbam, methacrifos, methamidophos, methidathion, mevinphos, monocrotophos, naled, omethoate, oxydemeton‐methyl, parathion, parathion‐methyl, phenthoate, phorate, phosalone, phosmet, phosphamidon, phoxim, pirimiphos‐ethyl, pirimiphos‐methyl, profenofos, propaphos, propetamphos, prothiofos, pyraclofos, pyridaphenthion, quinalphos, sulfotep, sulprofos, tebupirimfos, temephos, terbufos, tetrachlorvinphos, thiometon, triazophos, trichlorfon, and vamidothion.
California Pesticide Illness Surveillance Program
Authors: Mehler Louise
Published: November 2003

The State of California requires physicians to report all health conditions that they know or have reason to believe resulted from pesticide exposure. The Department of Pesticide Regulation (part of the California Environmental Protection Agency) investigates these reports and any other pesticide cases identified. This effort, the Pesticide Illness Surveillance Program (PISP), attempts to track any type of health effect attributable to any product registered or used as a pesticide, including antimicrobial sanitizers and disinfectants.

PISP scientists evaluate the incidents investigated and code case specifics in a computerized database. Data have been collected on more than 40,000 individual cases. Over 90% of the cases provide enough information to permit a judgment as to the likelihood that pesticide exposure caused or contributed to development of a health problem. Roughly two‐thirds of these are evaluated as at least possibly related to pesticide exposure. The PISP publishes annual data summaries and responds to inquiries from individuals, government agencies, advocacy groups, and industry.
Herbicides, Plant Hormone Mimics—Auxins
Authors: Friesen L. J. Shane , Van Eerd Laura L. , Hall Christopher
Published: November 2003

Synthetic auxins act in a very similar way to the natural plant hormone auxin, and they may become herbicidal to numerous plant species, i.e., causing an “auxin overload,” if applied at a sufficient dose. Many of these compounds have been synthesized over the past century, and some have been developed into potent commercial herbicides. Due to commercial success, chemical companies have pursued the development of other organic herbicides for use in agriculture, and thus have contributed to the creation of multi‐billion–dollar worldwide pesticide industry of today.
Pyrethroids
Authors: Pap László
Published: November 2003

The insecticidal synthetic pyrethroids are chemical analogs of the natural pyrethrins occurring in the flower of theChrysanthemum cinerariaefoliumplant. They represent an extensively developed insecticide group with 40 established compounds. Of the 40 commercialized active ingredients, 37 are esters.

The application rate of the most potent agricultural pyrethroids is very low, ranging between 5 and 20 g/ha, representing an acceptable environmental load. Pyrethroids are also regarded as safe compounds to warm‐blooded animals and generally to the environment; however, they have some adverse effects on mites, beneficial insects, and aquatic organisms. Pyrethroids are contact nerve poisons acting on gating kinetics of sodium channel in nerve membrane. This action is highly stereoselective. Due to this specific action and their extensive use, the risk of resistance development is relatively high in the targeted insect pest populations. Consequently, resistance management strategies are urgently needed to sustain their appropriate field performance. The registered tendencies of pyrethroid usage and the recent trends in R&D both suggest that this particular group of compounds has been playing an integrated part in present pest management as it is described in our comprehensive survey.

Natural Pyrethrin

PyrethrinI as the Lead Structure of the Synthetic Pyrethroids

Stereochemistry

How to Define Pyrethroids

Nomenclature

Physicochemical Properties

Agricultural Use

Chemistry

Biological Activity, Mode of Action, Metabolism
Remediation
Authors: Klein Kimiko , Underwood Marilyn
Published: November 2003

Remediation, as discussed in this article, refers to the cleanup of sites where hazardous materials, such as pesticides, have been released to the environment to the extent that concentrations in soil, water, or air could result in adverse health impacts to human and nonhuman receptors. The cleanup of sites may include removal actions, which take place quickly when there is an imminent threat to public health or the environment, or remedial actions, which take place after the results of extensive investigation indicate that long‐term exposure to the chemicals at the site could result in adverse health effects, such as cancer.
Agrochemicals: Developmental Toxicity/Reproductive Toxicity
Authors: Iyer Poorni , Schardein James L. , Makris Susan
Published: November 2003

Agrochemicals have been in use since the early days of modern agriculture. They have been well studied and subject to regulation by various federal and state agencies. There is growing concern about the safety of agrochemicals and how exposure may affect reproductive outcome in humans and other species. This article describes toxicity studies that focus on the developmental and reproductive systems of laboratory animals. The endpoints evaluated include infertility, birth defects (structural defects and functional deficits) and adverse effects on male or female reproductive systems. The classes of agrochemicals discussed include herbicides, insecticides, fungicides, rodenticides as well as fumigants and other miscellaneous chemicals used in agriculture. Data typically submitted to regulatory agencies for the purposes of registration are not readily accessible in the open literature and an attempt has been made to present the findings from such studies. Regulatory issues such as testing requirements and approaches to risk assessment of compounds resulting in adverse reproductive outcome are also outlined. Available epidemiological data on the developmental toxicity of occupational and environmental agrochemical exposure are limited in the sense that while a number of studies have some indications of elevated risk for specific compounds, the epidemiological evidence on the whole is unclear.
Herbicides, Plant Resistance to Herbicides
Authors: Hatzios Kriton
Published: November 2003

A growing number of weed species have evolved resistance to certain herbicides around the world, but the total area infested with resistant weed populations is still relatively small. Resistance to some herbicides occurs at a relatively high frequency within many weed populations, and continuous use of these herbicides will select for those variants. Herbicide resistance deriving from target site mutations has occurred rapidly to those herbicides that share most or all of the following characteristics: 1) a single site of action, 2) a high persistence in the environment, 3) a high level of efficacy in causing plant death, 4) a high rate of mutation of the active site, and 5) a less debilitating effect by alteration of this herbicidal site. The development of weed resistance based on other mechanisms of resistance, such as herbicide compartmentation or metabolism, is more difficult to predict, because in many cases the cellular factors involved in herbicide movement or sequestration are less well‐characterized than are those related to the site of action. The development of multiple‐resistance mechanisms is of particular concern, because fewer new herbicides are released and many of the new herbicides have sites of action or mechanisms of metabolism in common with older herbicides, to which resistance has already developed. Combining herbicides with other herbicides either in mixtures or in rotations will greatly extend the usefulness of herbicides for the farmer.
Risk Assessment and Risk Management
Authors: Cochran Roger C.
Published: November 2003

Risk is a function of toxicity and exposure. Regulatory agencies assess the risks associated with pesticide usage, and act to mitigate workers' and the public's exposures to acceptable levels. The regulatory actions assume that there is a high degree of certitude associated with the values calculated by the risk assessment process. In truth, the degree of uncertainty may be very great. Sources that contribute to the uncertainty of the numbers vary, and the magnitude of the imprecision varies as well. The ambiguities contained in the risk assessments by two regulatory agencies concerning chlorpyrifos, molinate, thiabendazole, and phosphine are presented to gain insight by example. Despite the detailed uncertainties, risk assessments are still needed by regulatory agencies. Various interest groups and politicians try to use the uncertainties in a risk assessment to justify their positions. The appropriate place to take into account the views of disparate interest groups is in the risk management process. Risk assessments will be disputed from all sides, the logic employed should be carefully layed out, and the assessor should strive for as much accuracy as science permits.
Soil Conditioners: Agricultural Applications
Authors: Valentine Don
Published: November 2003

Soil conditioners are materials that measurably improve the physical characteristics of the soil as a plant growth medium. Typical uses include erosion control, prevention of surface sealing, and improvement of water infiltration and drainage. Many natural materials such as peat and gypsum are used alone or in combination with synthetics for soil conditioning. This article is concerned with uses of synthetic soil conditioners, primarily synthetic polyelectrolytes such as polyacrylamides, in agriculture, horticulture, and related applications.
Soil, Movement of Pesticides in
Authors: Lennartz Bernd
Published: November 2003

Once chemicals released into the environment have reached the soil surface, they may be transported primarily horizontally via overland flow or vertically into the soil with the infiltrating rainwater. The horizontal solute transport at the soil surface following the minimal slope of the landscape poses a direct threat to the surface water quality because the soil with its buffer function is bypassed. Hazardous chemicals, such as pesticides, can be transported directly from the point of application to large water bodies via overland flow.
Soil Persistence
Authors: Bromilow Richard
Published: November 2003

The major loss process for most agricultural pesticides is degradation in soil. The need to safeguard against any damaging effects of undue persistence of pesticides in the environment has led to many studies to satisfy the registration requirements. This article considers the experimental methods to determine pesticide degradation in soil, including the mechanisms and pathways of degradation, which eventually lead to residues bound into the soil organic matter, together with mineralization to carbon dioxide. Rates of breakdown are determined not only by the intrinsic nature of the pesticide molecule, but also by other factors such as the route of application, the nature of the soil, climate, and the role of microorganisms. Laboratory studies of these factors aid in understanding and predicting the likely behavior in the field. Finally, the role of persistence has to be assessed, including an appraisal of whether a persistent pesticide will have any deleterious effects on following crops or on soil processes.
Standard Evaluation Procedures
Authors: Brooks Matthew W.
Published: November 2003

The most critical aspect of registering a new pesticide is the presentation of laboratory and field data. What data are required and how they are determined is described by several U.S. Environmental Protection Agency publications. This large article contains a great detail and presents the titles of the required tests, when they are required, and one what type of pesticide. The tests are further defined as those required on the pure active ingredient or on the end‐use product.
Storage Stability
Authors: Khetan Sushil K.
Published: November 2003

Modern agricultural formulations are usually complex mixtures of different organic and inorganic compounds. Over a period of time, these may undergo chemical or physical changes. The stability of an agrochemical product depends on the intrinsic stability of the active ingredient(s), the formulations, the packaging, and, in particular, the storage conditions. The storage stability or shelf life is defined as the length of time the product can be stored under normal local conditions, with changes in its properties and characteristics varying within predetermined, acceptable limits and remaining in a satisfactory and safe package and still giving the claimed biological activity.
Volatility Of Pesticides
Authors: Taylor Alan W.
Published: November 2003

Volatilization and chemical degradation are the principal causes of the loss of pesticide residues from target areas after application. Except in very special circumstances, the total seasonal losses in surface runoff and movement in eroding soil rarely exceed 5 or 10% of the total applied and the fraction removed by leaching is much less. Volatilization rates depend upon complex interactions between the chemical properties of the individual compounds, the properties of the soil or plant tissue on which they are adsorbed, and the weather, and—not least—they way in which they are applied and how the crop receiving them is managed.