Agricultural biotechnology has been a significant step forward inpest management in the United States. The range of its applications has been extensive and is expanding rapidly. The principal commercialised applications thus far include herbicide tolerance, insect resistance and virus resistance.Biotechnology-derived crops were first introduced for commercial production in the United States in the mid 1990s. In spite of the dichotomy of opinion regarding biotechnology-derived crops, adoption has been dramatically rapid in the United States since their introduction. The United States is the principal country that planted most of the biotechnology-derived crop acreage (68% of the global) followed by Argentina (22%), Canada (6%) and China (3%) in 2001 (James, 2001). In 2001, biotechnology-derived crops were planted on 88 million acres of US crop acreage, up by 18% compared to 2000 (James, 2001). James (2001) noted that adoption of biotechnology-derived crops has been the highest ever for new agricultural technologies and attributed this to grower satisfaction and significant benefits. Current trends suggest that in the next few years almost all acreage of the major crops grown in North America will be biotechnology-derived.
A conflicting aspect of agricultural biotechnology is the amount of public debate and furore it has generated. Opposing opinions regarding biotechnology-derived crops centre on different perceptions regarding their benefits, environmental and ecological safety, implications on human health and ethics. An understanding of the benefits of agricultural biotechnology for pest management is pivotal to judge the merit of the technology and to resolve the public discussion.
This chapter examines the importance of pest management in crop production and details the commercially available biotechnology-derived traits and their need in the context of available pest management options in conventional crops. The discussion is mainly focused on the actual and potential benefits of this innovation for crops commercialised so far in the United States. Economic advantage to growers is the ultimate key factor, which determines the adoption and success of biotechnology-derived crops. Economic benefits normally result from reduced input costs or increased yields or both.
Importance of Pests in Agriculture
Pest populations have been and will continue to be the major constraints to crop production in the United States. Based on a 1988–1990 estimate, the impact of weeds, insects and pathogens on the production value of eight major crops grown in North America was 11.4, 10.2 and 9.6%, respectively, amounting to a total of $23 billion (Oerke et al., 1994). A recent estimate suggests that impact of weeds alone on US economy exceeds $20 billion annually (Bridges, 1994).
Pest management in crops is a dynamic activity that evolves as new technologies are developed. Growers have relied on a variety of tactics such as manual methods, cultural practices, biological control, quarantine and pest-resistant cultivars to combat pests thus far. Use of chemicals replaced manual and cultural methods in the 1940s, after which crop productivity increased dramatically in the United States.
Weeds are a constant and major challenge to farmers worldwide. About 72% of the pesticides used in the United States are herbicides, 21% are insecticides and 7% are fungicides (Duke, 1998), which emphasises the importance of weeds as crop pests. Control of weeds is critical as they compete with crops for nutrients, water, sunlight and space resulting in significant yield and quality losses. Season-long weed infestations can result in severe yield losses depending on the competing weed species and their density. For example, corn yields were reduced 10% by giant foxtail, 11% by common lambsquarters, 18% by velvetleaf and 22% by common cocklebur at a density of two per foot of row (Beckett et al., 1988). Additionally, weeds increase the cost of agricultural production, reduce land use and human efficiency, and act as hosts for insects and pathogens thereby increasing their control costs. As a result, almost all of the acreage of major crops in the United States is treated with herbicides to avoid yield loss.
Insects infest crop plants for the most basic reasons: to obtain food or protection for overwintering and oviposition or to complete their life cycle. The direct impact of insects result from their feeding on plant parts, which leads to reduction in crop productivity and quality. Losses due to insects each year in the United States were estimated to be 13% or $33 billion (USBC, 1998). The concentrated large acreages of a single crop in successive years (monoculture) have led to a general increase in insect pest populations in the United States. Monocultures lead to unstable agroecosystems due to increased abundance of food supply, decreased competition, low diversity of insect pests and increased ease of locating food supply.
Pathogens that infect plants fall under diverse groups such as viruses, bacteria, fungi, algae, protozoans and nematodes. These pathogens cause harmful physiological and metabolic effects in crop plants thereby resulting in significant yield losses. For example, estimated crop losses due to diseases in the United States are over 10% (El-Zik and Frisbie, 1991). Annual crop losses to all plant pathogens total an approximate $33 billion in the United States (USBC, 1998).
Crop loss estimates due to various pests are often misleading as they represent average loss over a wide area of production. In reality, losses are usually much higher on individual farms. Thus, crop losses definitely justify research to explore new methods such as modern biotechnology to manage pest populations.
The following discussion centres on why growers have adopted biotechnology-derived crops. It outlines the shortcomings in conventional pest management and suggests how biotechnology-derived crops offer solutions to these problems. Finally, the benefits derived from the technology for specific crops are highlighted.
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