A. A pest is any organism that is noxious, destructive, or troublesome.
Fig. 17.2 Non-agricultural and agricultural use is shown for the time period of 1964-1995. (Data from Environmental Protection Agency.)
II. How Do We Respond to Pests?
B. Classes of Pesticides
1. First Generation - Inorganics
a. Metals (arsenic trioxide), Bordeaux mixture (copper sulfate, lime, and water),
sulfuric acid, Paris Green (copper arsenite), calcium arsenite
2. Second Generation - Organochlorines (DDT, toxaphene, dieldren)
a. Broad spectrum and persistent
b. Eliminated due to environmental consequences bioaccumulation
c. Don't know the mechanisms of action for many
3. Third Generation - Organophosphates and carbamates
a. Typically less persistent but more acutely toxic than the organochlorines
b. Primarily nerve toxins
4. Fourth Generation Life-cycle disrupters
a. Target a portion of the insect life-cycle to reduce pesticide population
b. May be endocrine disrupters for nontarget organisms
Fig. 17.4 Using pesticides causes selection (survival of the fittest) for those individuals that are resistant. As we continue to use pesticides, we breed insects and other pests that are increasingly resistant to the pesticides used against them.
Fig. 17.5 Food chains exist among insects just as they do among higher animals.
Fig. 17.6 The continued use of these products demands ever-increasing dosages of pesticides, which further aggravate pest problems and produce more contamination of foodstuffs and ecosystems.
III. What Results from Using Pesticides for Pest Control?
A. Quantity Used and Monetary Impact
B. Resource Impact - Pesticides are typically made from petroleum.
C. Crop Loss with and without Pesticide Use
1. In 1950: crop loss = 31%; in 1995 crop loss = 37%
2. Why is so much lost?
a. Monoculture cropping
b. Use of genetically identical plants
D. Problems Resulting from Pesticide Use
1. Pesticide Resistance
2. Pest Resurgence
3. Secondary Pest Outbreaks
4. Human Health Effects
a. Acute: high dose, short term exposure, rapid onset (headache, nausea,
vomiting, respiratory failure, death)
b. Chronic: low dose, long term exposure, outcome not seen for many years
(cancer, reproductive damage, immune dysfunction)
5. Environmental Health Effects
a. Bioconcentration - movement of a chemical against a concentration gradient
b. Biomagnification - movement of a chemical through a food chain
c. Bioaccumulation - bioconcentration plus biomagnification. This is a rare
combination but few exogenous chemicals bioconcentrate. Not only is the ability
to bioconcentrate found in chemicals that can bioaccumulate but the chemical is
typically fat soluble and persistent. Examples: DDT, PCBs, dioxin
Fig. 17.8 Each successive consumer in the food chain accumulates contaminants to a higher level. The concentration of the pesticide is magnified manyfold throughout the food chain. Organisms at the top of the food chain are likely to accumulate toxic levels.
Fig. 17.9 Like the moth shown here, most insects have a complex life cycle that includes a larval stage and an adult stage. Biological control methods recognize the different stages and attack the insect, using knowledge of its needs and life cycle.
IV. Alternative Pest Control Methods
A. Cultural Controls
1. Cultural Control of Pests Affecting Humans
2. Cultural Control of Pests Affecting Lawns Gardens and Crops
B. Control by Natural Enemies
1. The enhancement of natural enemies for the reduction of pest population size
1. Chemical Barriers - genetically controlled production of a toxic repellant chemical
by a desirable species
2. Physical Barriers - genetically controlled production of a physical trait that reduces
or eliminates the ability of a pest to damage the desirable organism
3. Sterile Males - release sterile males to compete with wild-type males in the mating
of wild-type females
4. Biotechnology - genetically engineering traits into species
D. Natural Chemical Control
1. Hormones: control of development
a. Juvenile hormones
b. Ecdysone hormones
c. Possible endocrine disrupters
a. Sexual attractants
Fig. 17.10 Part of the life cycle of wheat rust, a parasitic fungus that is a serious pest on wheat, requires that the rust infest barberry, an alternative host plant. The elimination of barberry in wheat-growing regions has been an important cultural control.
Fig. 17.11 This figure shows the life cycle of the parasitic wasp that uses the gypsy moth as its host.
V. Socioeconomic Issues in Pest Management
A. Pressure to Use Pesticides
1. Pesticide Treadmill
B. Integrated Pest Management (IPM)
1. Integral to sustainable agriculture
2. Includes everything from culture control, to balanced soil ecosystems
C. Organic Farming
1. It is more than not using pesticides food is grown in a sustainable manner
2. Identical with IPM, except IPM allows for the rare use of synthetic pesticides
VI. Public Policy
A. Changes in U.S. Policy
1. FQPA: "The following are the major requirements of the act:
a. The new safety standard is "a reasonable certainty of no harm" for substances
applied to food.
b. Special consideration must be given to exposure of young children to pesticide
c. Pesticides or other chemicals are prohibited if they can be shown to carry a risk
of more than one case of cancer per million people when consumed at average
levels over the course of a lifetime.
d. All possible sources of exposure to a given pesticide must be evaluated, not just
e. A special attempt must be made to assess the potential harmful effects of the
so-called hormone disrupters.
2. Pesticides in Developing Countries.
Fig. 17.5 The objective of pest control should not be its total eradication, but keeping population below the economic threshold.
Fig. 17.16 IPM helped Indonesian rice farmers bring the brown planthopper under control, after years on the pesticide treadmill.