eChapters

Introduction

Cereal crops are of global importance and the lifeline of the humane civilization. Nutritionally, they are important sources of dietary protein, carbohydrates, Vitamin B complex, Vitamin E, iron, trace minerals and fiber. Major cereal crops produced worldwide include wheat, rice, maize and millets. Among them, wheat, maize and rice together comprise at least 75% of the world’s grain production. More than 70 per cent of the cereal crop produced in developed countries is fed to livestock whereas, in developing countries, 68-98 per cent of the cereal crop is used for human consumption (Chaven and Kadam, 1989). Rice is the most important and widely cultivated crop in the world and is the staple food for about 60% of the world’s human population. It is basically a crop of humid tropics, but it varies widely in physiological adaptability, hence grown successfully both in tropical and temperate conditions. Wheat (Triticum aestivum L.) is the another important and widely cultivated food crop in the world and important rabi crop of our country. In India, wheat is the second stable food crop after rice which contains more protein than any other cereals. Maize is an important kharif cereal in hilly, sub-mountained and even in plain regions of our country where it forms staple diet of the people.

In practical agriculture, resistance represents the ability of a certain variety to produce larger crop of good quality than an ordinary variety at the same level of insect population. During the 19^th Century, the French wine industry survived a major set-back largely due to the use of resistant root stocks imported from America and which still maintain their resistance levels against the beetle pest (Painter, 1951). Another important example of resistant variety is the U-4 variety of cotton possessing high level of resistance to the jassid, Emposasca spp. (Parnell, 1925). The excessive use of pesticide on oilseed crops needs to be minimized owing to several reasons: (i) most of the pesticides are lipophilic and are likely to be carried in the oil (ii) in a few cases like Brassica, leaves and inflorescence are consumed as saag (pot herb), (iii) the oilseed crops provide the raw material for the vanaspati industry, cosmetics, etc., (iv) many of the oilseeds and oils are directly consumed without further processing, and (v) the oil cakes are used as cattle feed. Thus there is an urgent need to exploit the non-pesticidal methods of pest control, among which the use of resistant varieties assumes a great significance. The details of each oilseed crops are given below:

Introduction

Within the very small portion of the plant kingdom that includes the world’s crop plants, the legumes are a large group second to the cereals as sources of human food. Legumes belong to the family leguminosae with a group of bacteria, Rhizobium, which is able to utilize atmospheric nitrogen. This symbiosis which occurs in the root hairs may be the key to the success of legumes worldwide distribution. The family leguminosae includes about 18,000 species, characterized by their fruits, which are pods, by their (usually) alternate, pinnate or trifoliate leaves (Cobley and Steele, 1976). The diversity in the family ranges from hardwood trees of the tropical rain forests to the herbs of temperate pastures.

Introduction

Vegetables are preferable host to many insects because of their succulence and suitable nutritional status. All vegetables are attacked but degree of damage and number of pests varies depending upon the crop, variety and climate. Pest infestation in vegetables has been the main bottleneck in their economical production. The problem has more socio-economic dimensions because of rapid expansion of area under vegetables, intensive cultivation, round the year cultivation, export enhancement and health consciousness among the people.

The diamondback moth (DBM), Plutella xylostella (L.), is a major pest of brassica crops worldwide. DBM has been estimated globally to cost US$ 1 billion in direct losses and control costs. (Grzywacz et al., 2010)

Introduction

Biotechnology, in the recent years, has created unprecedented opportunities not only for the manipulation of biological systems for the benefit of mankind, but also to understand studies for better understanding of the fundamental life processes. Consequently, it has become the fastest and most rapidly growing technology in the world. As per US National Science Foundation, “Biotechnology is defined as any technique that uses living organisms or parts of organisms to make or modify products, to improve plants, amend animals or to develop microorganisms for specific uses”. Biotechnology offers new strategies that can be used to develop transgenic crop plants with improved growth, yield and quality and tolerance to biotic and abiotic stresses. By transgenic crop, we mean any plant containing a gene(s) which have been artificially inserted instead of the plant acquiring them through pollination. A plant in which a foreign gene has been transferred through genetic engineering is called transgenic plant and the gene so transferred is called transgenic. The inserted gene sequence known as transgene may come from another unrelated plant or from completely different species. Plants containing transgene are often called genetically modified or GM crops. Transgenic technologies have opened up many exciting possibilities to improve products with added value having application in food, agriculture, animal husbandry, environment, medicine and industry. It also offers uncommon opportunities for improvement in genetic potential of plants and animals by introduction or removal of gene(s) that regulate a specific trait.

Introduction

Worldwide damage due to insect pest attack accounts for 15 per cent crop losses, despite the use of insecticides which represents over US $100 billion (Krattiger, 1997). The annual cost of insect control itself amounts to US $8 billion, thus warranting immediate and economical control measures. The crop varieties developed in the past 30 years were high yielders, but unfortunately had poor storage characteristics and were highly susceptible to pest damage. Insect-pests are capable of evolving to biotypes that can adapt to new situations, for instance they overcome the effect of toxic materials or bypass natural or artificial plant resistance, which further confounds the problem (Roush and McKenzie, 1987). Under these circumstances, provision of food to the rapidly expanding population has always been a challenge facing mankind. This problem is more acute in the tropics and sub-tropics, where the climate provides a highly conducive environment for a wide range of insects and necessitates massive efforts to suppress the population densities of different pests in order to achieve an adequate supply of food. In developing countries, the problem of competition from insect-pests is further complicated with a rapid annual increase in human population (2.5-3.0 percentage) against a meager 1.0 per cent increase in food production. In order to feed the ever expanding population, crop protection plays a vital and integral role in the present day agricultural production to minimize yield losses. Currently, the crop protection practice in agricultural systems relies exclusively on the use of agrochemicals, although a few specific cases do exist, where inherent varietal resistance and biological control have been successfully employed. The exclusive use of chemical pesticides not only results in rapid build-up of resistance to such compounds, but their non-selectivity affects the balance between pests and natural predators, and is generally in favour of pests (Metcalf, 1986).

Fungi include a large group of organisms and there are about 72,000 described species and the total number of species in the world may be as high as 1.5 million (Hawksworth et al., 1995). The infections that these fungi cause on a group of organisms viz. plants, animals, insects etc. may or may not be beneficial depending upon the type of host infected. With reference to insects, fungal infections in pest insects are beneficial which can be used effectively in biocontrol programmes. On the other hand, fungal infections in beneficial insects are harmful.

The entomopathogenic or entomogenous fungi mainly include those genera of fungi that associate with insects and some arthropods in a variety of ways. The association with the insects may be saprophytic, commensalistic, parasitic or pathogenic with the insect host. Some entomopathogenic fungi like Coelomomyces are obligate pathogens which can’t be cultured outside a living host, but most of them are however, facultative pathogens capable of growing without host insect. More than 750 spp of fungi, mostly deuteromyctes and entomophthorales from about 100 genera are pathogenic on insects and many of them offer great potential for pest management. The entomopathogenic fungi which have been most intensively investigated include Beauveria, Metarrhizum, Paecilomyces, Entomophthora, Verticillium, Hirsutella, Eryina, Mefarrhizium etc. Out of them Beauveria and Mefarrhizium have been extensively used in large scale for the control of several crop pests.

Introduction

Horticulture is an intensive but profitable venture with higher output in terms of yield and income per unit area and time. In order to maximize the output, there has been liberal use of inorganic products like fertilizers, pesticides (insectides, fungicides, nematicides, weedicides) and other chemicals. With the continuous application of these chemicals since the last green revolution, the soil and its fertility is showing the sign of fatigue and plants developing resistance to insects, pests and diseases is breaking down and causing overall pollution to soil and water. There is growing evidence of sterility in humans and various other animals, particularly in males, related to the presence of various chemicals and pesticides in the environment. Hence the demand of the hour is looking for some alternative arrangements which are eco-friendly and moreover safe guarding the quality of the produce, which is essential so far as ornamentals are concerned. This is especially true for cut flowers and potted plants. Visible symptoms of insects, pests and diseases, have a major impact on quality. Direct and indirect effects of infections include reduction in growth, reduction in vigor, costs of attempting to maintain crop health, reduction in quality and/or market value (Hadidi et al., 1998). This may cause serious economic losses. In addition, infected plant material may not be acceptable for export.

Plant viruses are ultramicroscopic particles that multiply only within living cells and are potentially pathogenic while composed of nucleic acids surrounded by protein coat.

More than half of the known viruses cause diseases of plants. All plant species are probably susceptible to one or more plant viruses. Symptoms of virus infection may include stunting, yellowing, necrosis, mosaic, mottling, ring spots, or abnormal structures. Economic damage consists of reduced yield and quality.

Viruses neither divide nor produce any kind of specialized reproductive structures such as spores. Instead, they multiply by inducing host cells to form more viruses. Viruses causes disease not by consuming cells or killing them with toxins, but by utilizing cellular substances during multiplication, taking up spaces in cells, and disrupting cellular processes. These in turn upset the cellular metabolism and lead to the development of abnormal substances and conditions injurious to the functions and life of the cells or the organism. The property of transmissibility is an essential criterion for viruses. Plant viruses are transmitted from plant to plant in a number of ways. Mode of transmission includes vegetative propagation, mechanically through sap, seeds, pollen, dodder and by insects.

In the national and International scenario weeds continue to cause major problems in agriculture thereby, reducing yield and quality of crops by competing for the water, nutrients and sunlight essential for vigorous crop growth. Holm et al. (1997) listed about 200 weed species that cause 95% of weed problems for humans. As international travel and global trade increased, more plant species with potentially weedy traits are being moved around the world, giving rise to new, invasive weed problems, particularly in non-agricultural or natural ecosystems (Mack et al., 2000). The importance of weeds is reflected by the rapid growth of the use of chemical herbicides in agriculture throughout the world. The effectiveness of herbicides has dramatically increased yields in many cases and, in turn, stimulated development of new chemical herbicides. However, despite massive efforts, weeds continue to cause significant losses. These losses result from the selection and emergence of species that are not controlled by currently available herbicides, the inability of an herbicide to selectively control certain weedy species without injury to crop species, or the development of resistant strains. Among different management practices plant pathogens have also been suggested as one of several possible means of controlling the weeds that remain problematic or even as an alternative to chemical herbicides. Plant pathogens can be used to control weeds in a similar way to chemical herbicides. The term bio herbicide is coined to refer to herbicides based on any living organism (e.g. fungi, bacteria, viruses, protozoans). When the active ingredient used is a fungus, the product is called a mycoherbicide. Mycoherbicides can be applied in many ways, e.g. as aerial sprays, through ‘cut and paste’ application or in a powder form to be applied to the soil.

Proteinase inhibitors (PIs) are small proteins that are quite common in nature. They are natural, defense-related proteins often present in seeds and induced in certain plant tissues by herbivory or wounding (Koiwa et al., 1997). PIs are present in multiple forms in numerous tissues of animals and plants as well as in microorganisms. In plants they can be counted among the defensive mechanisms displayed against phytophagous insects and microorganisms. The defensive capacities of plant PIs rely on inhibition of proteases present in insect guts or secreted by microorganisms, causing a reduction in the availability of amino acids necessary for their growth and development. PIs are of common occurrence in the plant kingdom. Plant PIs (PPIs) are generally small proteins that have mainly been described as occurring in storage tissues, such as tubers and seeds, but they have also been found in the aerial parts of plants (De Leo et al., 2002). One of the important defense strategies that are found in plants to combat predators involve PIs which are in particular effective against phytophagous insects and microorganisms. The defensive capabilities of PPIs rely on inhibition of proteases present in insect guts or secreted by microorganisms, causing a reduction in the availability of amino acids necessary for their growth and development (Lawrence and Koundal, 2002).

Introduction

Indian agriculture accounts for nearly 65% of the country’s employment, 23% of the total GDP and nearly 20% of total export earning and supplier of raw material to major industries. Agriculture is not only the backbone of Indian economy and food security but also a way of life, a tradition and anchor of overall livelihood opportunity for about 700 million of our one billion populations. Agriculture, therefore, is and will continue to be central to all strategies for planned socio-economic development of the country.

Losses due to insect pests represent one of the single largest constraints to crop productivity estimated at 14% of the total agricultural production. Besides, insects also serve as vectors of plant pathogens. The annual global cost of pest management through insecticides is more than US$10 billion per annum. However, over-reliance of insecticides creates agricultural, environmental and pest management problems, such as frequent evolution of insect resistance, destabilization of multitrophic interactions and environmental contamination. Broad spectrum insecticides often compound these problems. Insecticides often interfere with biological control, causing secondary pest outbreaks or catastrophic resurgence of insecticide resistant herbivores. The vicious cycle of pesticide treadmill effect is observed when more pesticides lead to insects developing resistance, which in turn necessitates use of more and newer pesticides. Therefore, now it is imperative to develop a holistic system of tackling pests to make it more eco-friendly, economically viable and socially acceptable for the farmers.

Introduction

Globally, India takes pride of being one of the world’s largest producers of horticultural and agricultural commodities. The rapid increase in the area under intensive cultivation of crops, introduction of high yielding varieties, lack of natural enemy load of the pests and changing climatic conditions is largely responsible for the severe pest depredations. Pest management in agriculture is a challenging task in the context of increasing agricultural productivity without upsetting the ecological balance and deteriorating the environment. Use of agrochemicals in agriculture though played a significant role to boost the agricultural production is posing enormous problems like environmental pollution, pest resistance, pest resurgence, toxicity hazards, secondary pest outbreaks, residues in feeds, foods, soil and water, destruction of biodiversity of useful natural enemies and some social economic and political problems. In response, there has been increased demand for alternative and selective pest control agents. Biopesticides are advantageous due to their target specificity, eco-safety, no development of resistance, reduced number of applications, yield and quality improvement, higher acceptability and value of produce for exports and suitability for rural areas.

Introduction

The development of insecticide resistant populations of insect-pests, evidence of resistance, resurgence and environmental concerns have led to increased research for the alternative strategies to pesticides for control of damaging pest populations. Classical biological control and the success in that area are important and provide background and encouragement for increased efforts in the manipulation of natural enemies. Methods for manipulation of natural enemies for the purpose of reducing herbivore populations and alleviating plant stress include conservation and augmentation, habitat management and genetic manipulation.

Virtually all pest populations are affected by natural enemies to some extent. In many cases, natural enemies are the primary regulating force of the pest populations. Natural controls include effects of natural enemies (predators, parasites, pathogens), other biotic (living) factors such as food availability and competition, and abiotic (non-living) factors such as weather and soil. In pest management, biological control usually refers to the action of parasites, predators or pathogens on a pest population which reduces its numbers below a level causing economic injury. Herbivorous insects and pathogens that attack pest weeds are also considered biocontrol agents. Biological control is a part of natural control and can apply to any type of organism, pest or not, and regardless of whether the biocontrol agent occurs naturally, is introduced by humans, or manipulated in any way. Biological control differs from chemical, cultural, and mechanical controls in that it requires maintenance of some level of food supply (e.g., pest) in order for the bio-control agent to survive and flourish. Therefore, biological control alone is not a means by which to obtain pest eradication.

Introduction

Pheromones are chemicals emitted by living organisms to send messages to individuals of the same species. The class most widely explored are the sex pheromones produced by female moths which are used to attract conspecific males for mating. Bombykol, the sex pheromone of the silk moth, was first synthesized in 1959.

During the past 40 years, pheromones of hundreds of insect species have been chemically elucidated, including the sex pheromone of the codling moth. Its main component is (E, E) 8, 10-dodecadien-1-o1, a primary alcohol containing a straight chain of 12 carbons and two conjugated double bonds. Other moth pheromones are hydrocarbons, epoxides, acetates or aldehydes. These molecules all vaguely resemble fatty acids, from which they are indeed biogenetically derived.

Most pheromones consist of blends of two or more chemicals which need to be emitted at exactly the right proportions to be biologically active. The female effluvia or sex gland can contain additional compounds which are related to the pheromone components and whose biological function is often unclear. On the other hand, many attractants of male moths have been discovered simply by field screening. In several cases it could later be shown that the attractant found with this technique was identical to the natural pheromone produced by the female. In most others, the composition of the true pheromone is still unknown.

Introduction

The concept and impetus for IPM grew out of the discontent with using a purely insecticidal approach to insect control in many areas in the mid of twentieth century. Excessive use of pesticide and growing needs of people has triggered several consequences such as resistance and resurgence of pests, destruction and elimination of natural enemies, effect on non target organisms, environmental pollution, disruption in food cycle and food web and residues in food commodities and pesticide poisoning. Less knowledge about biocontrolagents/natural enemies and their non-availability at right time is the key hurdles for farming communities to adopt the IPM practices on their farm. However, pesticides are still a significant component of many control programs and their negative environmental and health impacts have stimulated the research to develop alternate pest management strategies, such as biological control (BC) and other compatible, safe and sound control practices. Some remarkable early successes for both the control of insect pests and weeds (e.g. the cottony cushion scale Icerya purchase (Maskell) by the vedalia beetle Rodolia cardinalis (Mulsant) in California; the prickly pear cactus Opuntia stricta (Haw.) by the moth Catoblastis cactorum (Berg) in Australia certainly were an impetus for further research in BC field. Although the levels of success have been variable, biological control is still considered as an important means of pest control, either alone or as component of integrated management programs (Jervis, 2005; Wajnberg et al., 2007).

Introduction

The integrated nature and high diversity of the soil health system may contribute a significant degree of resilience under conditions of disturbance, particularly at lower (largely microbial) trophic levels. Nonetheless, the conversion of natural vegetation to agricultural land results in major changes in both physical organization and community structure in the soil, including species loss and changes in dominance among the surviving biota. This then becomes the resource with which agriculture must work and any targets should realistically be set in relation to the potential equilibria in agricultural systems rather than the natural systems from which they are derived, as has sometimes been advocated. More importantly, it is clear that subsequent agricultural practices may also impair soil health through significant impacts on the composition and structure of the soil biological community and consequently on soil-based ecosystem functions and services. Damage to ecosystem functions can arise both owing to an inadequate supply of resources (carbon, energy, nutrients or water) and through the impact of intensive substitutive practices such as continuous mechanical tillage, the use of pesticides and excessive amounts of fertilizers. These interventions may also impact on soil functions by destroying or changing the habitat of the soil organisms and their capacity to repair it.

Introduction

The main reliance is on the use of insecticides to reduce the losses. The insecticides are the major component of “Integrated Pest Management” (IPM) in almost all the agro-ecosystem. Cotton, paddy, vegetables and fruits are grown in 32% of the cultivated area and account for over 80% of the pesticide consumption in the country. From a modest beginning in 1947, when DDT was first used for malaria control, pesticide consumption in India has grown to a total market size of over Rs. 45000 million in 2003. The total installed capacity of technical grade pesticides is approximately 140,000 tpa. Out of the 204 pesticides registered in the country, 66 technical grade pesticides are manufactured in India.

Weeds pose serious problems to agriculture and environment. Weeds are plants that are undesirable to human activity at a particular time and place, and therefore, weeds will always be associated with human endeavours. In agriculture these not only cause huge reductions in crop yields but also increase cost of cultivation, reduce input efficiency, interfere with agricultural operations, impair quality, act as alternate hosts for several insect pests, diseases and nematodes. In non-crop areas, they affect aesthetic look of the ecosystem as well as native biodiversity and health and quality of life. Weeds are a big constraint in crop production and are responsible for heavy yield losses in almost all the crops. “Being fore-warned is fore-armed” is the principle behind preparation of perspective plans. Weeds are big constraints in crop production and are responsible for heavy yield losses in all crops. Out of the losses due to various biotic stresses, weeds are known to account for nearly one third. Proper management of weeds is essential to meet the growing demand of foodgrains, pulses, oilseeds and other crops by the ever increasing population. As per the projections of IFPRI, Washington there is a likelihood of shortfall of 41 per cent in the food grain production in the country by 2020.

Introduction

The increasingly precarious situation facing the world’s hill regions has been the focus of a growing level of awareness over the past two decades. The high altitude regions offer a challenge to agricultural development agencies which is shared by many hill areas of the world characterized by marginality, extreme diversity, environmental fragility and complex smallholder farming systems. There is justifiable concern relating to the conservation of hill and mountain ecosystems, to the extent that the concept of sustainability has been adopted as a broad slogan by the environmental movement (Lele, 1991).

Conditions specific to mountain regions, such as inaccessibility and diversity have placed a high premium on large families, encouraging population growth. Children are essential to family subsistence strategies offering free labour, and they are consequently considered to be a source of wealth. Population control measures in these regions have ignored this scenario (Sharma and Banskota 1990; Jodha, 1991).