Encyclopedia of Global Resources part 64 provides a wide variety of perspectives on both traditional and more recent views of Earth's resources. It serves as a bridge connecting the domains of resource exploitation, environmentalism, geology, and biology, and it explains their interrelationships in terms that students and other nonspecialists can understand. The articles in this set are extremely diverse, with articles covering soil, fisheries, forests, aluminum, the Industrial Revolution, the . Department of the Interior, the hydrologic cycle, glass, and placer mineral deposits. . | 578 Horticulture Global Resources Pest Control Since plants are besieged by a panoply of biological agents that utilize plant tissues as a food source plant protection from pests is a major concern in the horticulture industry. Microbial organisms nematodes insects and weeds are the major plant pests. Weeds are defined as unwanted plants and are considered to be pests because they compete with crop plants for water sunlight and nutrients. If left unchecked weeds will drastically reduce crop yields because they tend to produce a large amount of seed and grow rapidly. Weed control is generally accomplished either by removing the weed physically or by use of a variety of herbicides that have been developed to chemically control weeds. Herbicides are selected on the basis of their ability to control weeds and at the same time cause little or no damage to the desired plant. Plant protection from microbes nematodes and insects generally involves either preventing or restricting pest invasion of the plant developing plant varieties that will resist or at least tolerate the invasion or a combination of both methods. The application of chemicals utilization of biological agents isolation of an infected crop by quarantine and cultural practices that routinely remove infected plants or plant tissues are examples of the different types of control methods. A large number of different bactericides fungicides nematocides and insecticides have been developed in recent years and the use of these pesticides has been particularly useful in plant protection. Since many of these chemicals are harmful to other animals including humans the use of pesticides and insecticides in particular requires extreme caution. There is an increasing interest in the use of biological control methods because many of the chemical pesticides pose a threat to the environment. The development and use of pest-resistant crop varieties and the introduction of natural enemies that will not only reduce the pest
