Table of Contents:
Insecticide and Miticide Pest Controls
In general, insecticide and miticide control of insects and mites return ~$4 for every $1 invested in chemical control.111 This is an excellent return, but not as high as some of the nonchemical controls. For example, biological pest control has reported earnings of $100-$800 per $1 invested in pest control. It must be recognized that the development of biological controls, although highly desirable, are not easy to develop and implement.
Both in crops and nature, host plant resistance and natural enemies (parasites and predators) play an important role in pest control. In nature, seldom do insect pests and plant pathogens remove >10% of the resources from the host plant. Host plant resistance, consisting of toxic chemicals, hairiness, hardness, and combinations of these, prevents insects from feeding intensely on host plants.151 Some of the chemicals involved in plants resisting insect attack include cyanide, alkaloids, tannins, and others. Predators and parasites that attack insects play an equally important role in controlling insect attackers on plants in nature and in agro ecosystems.
Insect Transmission of Plant Pathogens
Insects with sucking mouth parts, such as aphids and plant bugs, play a major role in the transmission of plant pathogens from plant to plant. It is estimated that ~25% of the plant pathogens are transmitted by insects. The most common pathogens transmitted are viruses. These pathogens include lettuce yellows and pea mosaic virus. Fungal pathogens are also transmitted by insects. For example, Dutch elm disease is transmitted by two bark beetle species that live under the bark of elm trees. In infected trees, the bark beetles become covered with fungal spores. When the beetles disperse and feed on uninfected elm trees, they leave behind fungal spores that in turn infect the healthy elm trees.
Environmental and Public Health Impacts of Insects
Some insect species have become environmental and public health pests. For example, the imported red fire ant kills poultry chicks, lizards, snakes, and ground-nesting birds. Investigations suggest that the fire ant has caused a 34% decline in swallow nesting success as well as a decline in the northern bob white quail populations in the United States. The ant has been reported to kill infirm people and people who are highly sensitive to ant sting. The estimated damages to wildlife, livestock, and public health in the United States is >$1 billion per year, with these losses occurring primarily in southern United States.131
In another example, the Formosan termite that was introduced into the United States has been reported to cause >$1 billion per year in property damage, repairs, and controls. As it spreads further in the nation, the damages will increase.131
Insect and mite pests in the United States and throughout the world are causing significant crop, public health, and environmental damages. Just for crop losses in the United States, it is estimated that insect and mite species are causing $37 billion per year, if control costs are included. Worldwide crop losses to insects and mites are estimated to be $400 billion per year. The public health and environmental damages in the United States and throughout the world are estimated to be valued at several hundred billion dollars per year.