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22
Pests and Pesticides:
Growing Crops Sustainably
Chapter Outline
Chemical Pesticides
Modern Chemical Pesticides
Growth in the Use of Chemical Pesticides
Overuse
Biological Impacts of Pesticides
The Economic Costs of Pesticide Use
Herbicides in Peace and War
Peacetime Uses: Pros and Cons
The Alar Controversy: Apples, Alar, and Alarmists?
Controlling Pesticide Use
Bans on Pesticide Production and Use
Registering Pesticides
Establishing Tolerance Levels and Monitoring Produce
Integrated Pest Management: Protecting Crops Sustainably
Environmental Controls
Genetic Controls
Chemical Controls
Cultural Controls
Educating the World About Alternative Strategies
Governmental Actions to Encourage Sustainable Agriculture
Key Terms
chemical pesticides first-generation pesticides second-generation pesticides
broad-spectrum pesticides narrow-spectrum pesticides chlorinated hydrocarbons
organic phosphates carbamates genetically resistant insects
biomagnification herbicides insecticides
integrated weed management agent orange registration
licensed applicators tolerance levels integrated pest management
heteroculture crop rotation biological control
sterile male technique third-generation pesticides pheromones
confusion technique juvenile hormone molting hormone
cultural controls
Objectives
1. Discuss the historical development of pesticides including all three “generations” of pesticides.
2. Discuss the three types of synthetic organic pesticides and give examples of each type.
3. Summarize the biological impact of chemical pesticide use.
4. Discuss the advantages and disadvantages of herbicide use.
5. Define the following terms: “integrated weed management” and “integrated pest management.”
6. Discuss the effectiveness of the Federal Insecticide, Fungicide, and Rodenticide Act in regulating pesticide use.
7. Discuss the techniques used in integrated pest management.
Lecture Outline
Chemical Pesticides - Pest control measures have been used throughout the centuries. They have consisted of chemicals and cultural controls.
Modern Chemical Pesticides
Pesticides are pest-killing chemicals.
First-generation pesticides were simple but mostly either toxic or ineffective.
Second-generation pesticides began with DDT; these are synthetic organic compounds, of which thousands have been developed.
Synthetic pesticides may be either broad- or narrow-spectrum, depending on their specificity.
Pesticides fall into three chemical families: chlorinated hydrocarbons, organic phosphates, and carbamates.
Growth in the Use of Chemical Pesticides
Several million tons of pesticides are used each year, mostly in the developed nations. The bulk of the pesticides used are herbicide.
Overuse
Pesticides are often applied in excess, which increases the danger of their use.
Biological Impacts of Pesticides
Harmful biological impacts of pesticides include: destruction of beneficial insects, development of genetically resistant pests, and health effects in nontarget organisms and humans, especially chemical and farm workers, rural residents, and consumers.
The Economic Costs of Pesticide Use
Pesticides have caused considerable economic damage especially from poisonings, death, and loss of wildlife.
Herbicides in Peace and War
Sixty percent of all pesticides used are herbicides.
Peacetime Uses: Pros and Cons
The benefits of herbicides are listed below.
They decrease the amount of cultivation needed to control weeds and thereby reduce operating costs.
They reduce weed damage when soils are too wet to cultivate because crops can be sprayed by plane.
They reduce water usage because water evaporates more quickly from ground that has been cultivated to control weed growth.
The disadvantages of herbicides are summarized below.
Resistant weeds may proliferate and necessitate further application of herbicide.
Resistance to the herbicide is developed and creates a more severe problem.
Herbicides encourage accumulation of material on the ground that is good for growth of pest populations (dead plant material). Herbicide use may actually increase insect pest problems necessitating the use of insecticides.
Herbicides can reduce the farmer’s incentive to rotate crops, which can allow pests to increase.
Herbicides can decrease some plants’ resistance to insects and disease by damaging the plants’ tissues, changing their metabolic rates, and affecting rate of growth. All of these factors could make plants more susceptible to insects and disease.
Some herbicides are toxic and may cause birth defects, cancer, and other illnesses in animals including humans.
Extensive use of chemical defoliants (Agent Orange) during the Vietnam War resulted in substantial environmental and health impacts. The human health effects are attributed to dioxins that contaminate the herbicide.
The Alar controversy: Apples, Alar, and Alarmists?
Children may be at higher risk to pesticides than adults.
Controlling Pesticide Use
Bans on Pesticide Production and Use
Bans on harmful pesticides in the United States have been effective. The ban on DDT has allowed the recovery of a number of endangered bird species.
Bans on pesticides in the United States are only part of the answer. Many imported vegetables and fruits have been found with pesticide contamination.
Global bans of harmful pesticides will be necessary to have significant impacts here and abroad.
Registering Pesticides
The United States EPA registers newly developed and previously introduced pesticides for general or restricted use. They can stipulate what crops they can be used on in the registration process. Improvements are needed in the registration process. For instance, the process does not require testing for neurotoxicity or toxicity to the immune system.
Establishing Tolerance Levels and Monitoring Produce
Tolerance levels are concentrations of pesticides in or on foods that are believed to be a tolerable health risk. The EPA sets these levels in the United States.
The United States Food and Drug Administration and state agricultural agencies are charged with enforcement of the EPA standards.
The programs for monitoring/enforcement are under-funded and understaffed.
The EPA ranks pesticides in food as one of the nation’s most serious health concerns.
Integrated Pest Management: Protecting Crops Sustainably - This system calls for the integrated use of environmental, genetic, chemical, and cultural pest control; with properly educated farmers and increased pest monitoring, results can be impressive.
Environmental Controls - These alter the environment to disfavor the pests.
Increasing Crop Diversity
Heteroculture and crop rotation help prevent rapid growth of pest populations.
Altering the Time of Planting
This technique can thwart pests by removing their food supply.
Altering Plant and Soil Nutrients
By manipulating nutrient levels in soils and thus plants, some pests can be suppressed.
Controlling Adjacent Crops and Weeds
This can help control pests by either eliminating food or habitat for them or by luring them off more valuable crops.
Introducing Predators, Parasites, and Disease Organisms
Use of these techniques mimics or supplements natural biotic environmental resistance factors that regulate pest populations.
Genetic Controls
Sterile Male Technique
This involves releasing sterilized males of the pest species, which mate with wild females who thus do not produce offspring.
Developing Resistant Crops and Animals
Genetic engineering and artificial selection can lead to the development of pest resistant crops and livestock.
Chemical Controls
Second-Generation Pesticides
With judicious, timely, and appropriate application of low-toxicity, specific, and non-persistent pesticides, many of the benefits of these chemicals can be retained without accompanying ecological and human health damage.
Third-Generation Pesticides
Pheromones, insect hormones, and natural insecticides can, in some cases, effectively control pests without unintended environmental or human damage.
Cultural Controls - These various techniques offer alternatives to harsh chemical pesticides and are often quite effective.
Monitoring
Frequent pest monitoring is a necessary prerequisite to successful IPM.
Educating the World About Alternative Strategies
Both governments and nongovernmental organizations have an important role to play in educating growers and government officials about the alternatives to traditional pest management strategies.
Governmental Actions to Encourage Sustainable Agriculture
Governments can help promote sustainable agriculture by providing low-cost crop insurance for farmers who are making the transition to integrated pest management.
Governments can also help by developing organic certification programs. States like Colorado and California already have these programs working.
Suggestions for Presenting the Chapter
Ÿ Instructors should emphasize that there are alternatives to our use of conventional agricultural techniques. Integrated pest management as a part of an organic agricultural system is the wave of the sustainable future.
Ÿ Public and governmental support of sustainable agricultural practices is necessary to make the transition from our current unsustainable system to a sustainable agricultural system. Students need to be encouraged to support organic production.
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