Plant Nematodes of Agricultural Importance: A Colour Handbook PDF

Preface

Soil and plant nematodes are one of the most numerous groups of organisms occurring in the soil. They are microscopic animals and, with a few exceptions, are not visible to the naked eye. The majority of the soil-borne nematodes are not pests of crops and feed on other organisms, particularly bacteria and fungi. Those that are parasitic on crop plants can be very damaging and, because of their microscopic size, associating them with crop damage is therefore mainly dependent on determining the symptoms of their effects on plants or plant growth. Some of the parasitic nematodes do produce characteristic and recognizable symptoms of damage but many of them only produce nonspecific symptoms. The damage and the symptoms caused can be visible above-ground; however, apart from poor growth and yield of the plants, the specific nematode-induced damage symptoms can often only be seen in the below-ground plant organs, mainly the roots, rhizomes, bulbs, corms, and tubers.

When the above-ground symptoms are the result of nematodes feeding on roots below ground, these symptoms are often similar to those seen when there are water or nutrient deficiencies in the soil. These socalled poor soils or ‘tired soils' are often a result of a build-up of large populations of parasitic nematodes in the soil. The main above-ground symptoms of nematode root damage are poor or stunted growth, reduced foliage, twig/branch dieback, chlorosis or yellowing of leaves, poor fruit or seed production and, in extreme cases, wilting and early senescence or death of plants. The below-ground symptoms are related to the health of the root systems and other structures which can be reduced in number, suffer from necrosis and rot, or have abnormal growths such as swellings or galling. Generally, it is necessary to examine roots and other plant tissues to establish a connection between damage symptoms and nematodes. To be certain of the association between particular nematodes, the organisms have to be extracted from the soil, roots, or other plant material and identified microscopically.

This book is written to help people working with plants to have an improved understanding of plant nematode pests and enable them to give better informed diagnoses, where possible, of the damage caused by the very wide range of nematodes that are known to parasitize and injure plants. The colour photographs provide an extensive range both of symptoms of nematode injury and of nematodes themselves, observed in the field or microscopically in plant tissues, throughout the world. There is an introductory chapter on biology and parasitism. Parasitic nematodes are discussed under the crops that they are known to attack. Crop chapters are divided into grain legumes, vegetables, flowers, cereals, root and tuber crops, and tree, plantation, and cash crops. Concise information is provided for the nematodes in these crop sections on their distribution, symptoms and diagnosis, management, and identification. A final chapter outlines the common methods used in nematology.

A glossary of nematological terms and a bibliography of the most important nematology texts and papers have also been produced to help the reader.

In the compilation of this book, we are grateful to our nematological colleagues for their advice, support, and encouragement. We also wish to thank those who have generously allowed us to use their photographs; these persons are acknowledged specifically in the legends of the photographs. Lastly we thank Monica and Marylou, our long-suffering wives, for their patience and support of our efforts.