Biological Control Of Weeds With Plant Pathogens

It is appropriate at this time to reflect on two decades of research in biological control of weeds with fungal plant pathogens. Some remarkable events have occurred in the last 20 years that represent a flurry of activity far beyond what could reasonably have been predicted. In 1969 a special topics review article by C. L. Wilson was published in Annual Reviews of Phytopathology that examined the literature and the potential for biological control of weeds with plant pathogens. In that same year, experiments were conducted in Arkansas that determined whether a fungal plant pathogen could reduce the infestation of a single weed species in rice fields. In Florida a project was under way to determine the potential use of a soil-borne plant pathogen as a means for controlling a single weed species in citrus groves. Work in Australia was published that described experiments that sought to determine whether a pathogen could safely and deliberately be imported and released into a country to control a weed of agricultural importance. All three projects were successful in the sense that Puccinia chondrillina was released into Australia to control rush skeleton weed and was released later into the United States as well, and that Colletotrichum gloeosporioides f.sp. aeschynomene and Phytophthora palmivora were later both marketed for the specific purpose of controlling specific weed species.

Biological balance. The biological world. Attributes of a successful parasite. Types of biological interactions. Man, the disrupter of balance. The changing scene. Factors involved in biological control. A plant pathologist's definition of biological control. Comparative approaches to biological control of plant pathogens and insects. Applying biological control. Biological control in plant pathology. The stature of biological control of plant pathogens. Resident antagonists. Managing the biological balance. Biological control by resident organisms and introduced organisms. Host resistance. Ecological manipulation to control weed molds and pathogens of mushrooms. Approaches to biological control with antagonistic microorganisms. Selecting soil as a source of antagonists. Antagonistic populations of whole soils. Presumptive tests of antagonists in agar culture. Tests in soil. Testing mixtures of antagonists. Plant of action. Role of the pathogen in biological control. Ways the pathogen can overcome antagonism. Vulnerability during dormancy and saprophytic growth. Populations of soilborne pathogenic fungi that produce disease. Stimulation of antagonists by the pathogen. Control of nematodes by altering the sex ratio. Role of the antagonist in biological control. Biological efficiency of saprophytic organisms. Kinds of antagonists. Forms of antagonism. The ideal antagonist. Inoculation with avirulent organisms related to the pathogen. Recontamination of soil. Biological buffering by resident antagonists. Role of the host in biological control. Root dynamics. Physical and chemical features of the rhizosphere. Root exudation and the rhizosphere effect. Cropping history and the microbiological balance of soil. Plant residues. The host as a reservoir of inoculum. Decoy, trap, and inhibitory plants. Role of the physical environment in biological control. environment operative through the host and during dormancy of the pathogen. Environment operative during growth of the pathogen. Using environment for prediction. Using environment to nudge the biological balance. Integration between biological and chemical control. Biological control of pathogens of aerial parts. Microorganisms on aerial parts. Pathogens on aerial parts. Exudation to external surfaces. Natural dissemination of epiphytes. Whither biological control?. Stage in pathogen cycle to apply biological control. Agroecosystems in relation to biological control. Applying, activating, or assisting antagonists. Large-scale production of antagonists. Integrated control. Why biological control?. The role of biological control in plant pathology.

Publisher Description

Microbiology may be described as one of the younger sciences with its history, as a precise subject, only dating as far back as Pasteur in the mid 1800s and his revelation both of the role of microorganisms in nature and their importance to human welfare. Medical scientists rapidly took up the challenge, with their area of microbiology flourishing and expanding almost in complete isolation from the rest of biology. We now know, of course, that microorganisms have always played an important, if not essential role, in the biosphere with fermented foods and beverages, plant and animal diseases and nutrient cycling foremost in their sphere of activities. Within the last twenty years, microbiology has received two enormous boosts with the developments in microbial genetics and genetic engineering probably being the most influential, and the greater awareness of pollution and environmental sustainability following a close second. In 1990, your editor had the privilege and pleasure of being elected as President of The Association of Applied Biologists in the United King dom and, as the topic for his three-day Presidential Conference, chose 'The exploitation of microorganisms in applied biology'. This meeting stimu lated great interest in a wide range of subject areas, from weed control to nematology, from plant breeding to plant pathology, from mushrooms to mycorrhiza. The proceedings of this meeting were published in Aspects of Applied Biology, No. 24, 1990.

Biological Control in Agricultural IPM Systems covers the proceedings of the 1984 symposium on Biological Control in Agricultural IPM Systems, held in the Citrus Research and Education Center of the University of Florida at Lake Alfred. The symposium summarizes the status and practical use of biological control in agricultural integrated pest management (IPM) systems in the United States. The book is organized into seven parts encompassing 31 chapters that cover the biological control of arthropods, weeds, plant pathogens, and nematodes. After briefly discussing the status and issues of biological control in IPM, the book deals with the basic principles of IPM programs and their related costs, risks, and benefits in biological control. The text also describes the compatibility of plant resistance with biological control of arthropods and the chemical mediated host or prey selection behaviors of entomophagous insects attacking herbivorous insect pests. It explains the development of microbial insecticides; the genetic improvement of insect pathogens; the use of entomogenous nematodes in cryptic and soil habitats; and the techniques for integrating the influences of natural enemies into models of crop/pest systems. The fourth part of the book focuses on the biological control of weeds. The following part considers the general concepts relating to the unique characteristics of plant diseases affecting aerial plant parts. This part also examines the biological control of soil plant pathogens in IPM systems and the use of soilborne viruses, bacteriocins, and hypovirulent strains of fungi as biological control agents. The concluding parts describe the biological control of nematodes and the status and limits to biological control in selected commodity IPM systems, such as citrus, grapes, alfalfa, cotton, and soybean. Entomologists, plant pathologists, weed scientists, nematologists, toxicologists, and economists will find this book invaluable.

This book enhances our understanding of biological control, integrating historical analysis, theoretical models and case studies in an ecological framework.