Cunningham - Cunningham - Saigo: Environmental Science 7 th Ed. Pest Control Chapter 12.

Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

Pest Control

Chapter 12


Outline:

• Pests• Pesticides

Use and Types Benefits Problems Alternatives Reducing Exposure Regulating Use


PESTS AND PESTICIDES

• Biological Pests - Organisms that reduce the availability, quality, or value of resources useful to humans. Only about 100 species of organisms

cause 90% of crop damage worldwide.- Insects are most frequent pests.

Make up three-fourths of all species. Generalists

Compete effectively against specialized endemic species.


Pesticides

• Pesticide - Chemical that kills (repels) pests. Biocide - Kills wide range of organisms. Herbicide - Kills plants. Insecticide - Kills insects. Fungicide - Kills fungi. Acaricide - Kills mites, ticks, and spiders. Nematicide - Kills nematodes Rodenticide - Kills rodents. Avicide - Kills birds.


PEST CONTROL HISTORY

• Sumerians controlled insects with sulfur 5,000 years ago.

• Chinese describe mercury and arsenic to control pests 2,500 years ago.

• People have used organic compounds and biological controls for a long time. Romans burned fields and rotated crops to

reduce crop disease.


Synthetic Chemical Pesticides

• Modern era of pest control began in 1934 with DDT. Cheap, stable, soluble in oil, and easily

spread over a large area.- Highly toxic to insects, but relatively

nontoxic to mammals. Paul Mueller received Nobel prize in

1948 for the discovery.


PESTICIDE USES AND TYPES

• Pesticide use has increased dramatically since WWII. Almost nothing in 1950 to $33 billion for

2.6 metric tons in 1999.- 90% of pesticides are used in agriculture

or food storage and shipping. In US, household applications represent

12% of all pesticide use, but almost 23% of insecticide use.


Pesticide Types

• Inorganic Pesticides - Broad-spectrum, generally highly toxic, and essentially indestructible. (arsenic - copper) Generally neurotoxins

• Natural Organic Pesticides (Botanicals) - Generally plant extracts. (nicotene - phenols)

• Fumigants - Small molecules that gasify easily and penetrate materials rapidly. (carbon tetrachloride - ethylene dibromide)


Pesticide Types

• Chlorinated Hydrocarbons - Fast acting and highly toxic to sensitive organisms. (DDT - mothballs) Inhibit nerve membrane ion transport and

block nerve signal transmission. Persistent - Tend to biomagnify.

• Organophosphates - Extremely toxic to mammals, birds and fish. (Malathion) Outgrowth of nerve-gas research. Inhibit neurotransmitter enzyme.


Pesticide Types

• Carbamates - Similar to organophosphates. (Sevin). - Extremely toxic to bees.

• Biological Controls Microbial agents Bacteria Parasitic Wasps


PESTICIDE BENEFITS

• Disease Control Many insects serve as disease vectors.

- Malaria, Yellow Fever• Crop Protection

Using pesticides, pre-harvest losses to diseases and pests are at 30%, with post-harvest losses at an additional 20-30%.

In general, farmers save an average of $3-$5 for every $1 spent on pesticides.


PESTICIDE PROBLEMS

• Non-Target Species Up to 90% of pesticides never reach

intended target.• Pesticide Resistance

Resistant members of a population survive pesticide treatment and produce more resistant offspring.

- Pest Resurgence


Pesticide Resistance

• UN reports at least 500 insect pest species and 250 weeds and plant pathogens have developed chemical resistance. Farmers must continually change dosages

or chemicals to fight resistant pests.- Increasingly, pests are being found to be

resistant to chemicals they have not been exposed to.

Genetically-engineered crops likely to exacerbate the problem.


Pesticide Resistance


Creation of New Pests

• Broadcast spraying is also likely to kill beneficial predators. Under normal conditions many herbivorous

pests are controlled by natural predators.• With advent of chemical pest controls,

farmers have tended to abandon traditional methods of pest/pathogen control. Mixed crops and rotation regimes.


Environmental Persistence and Mobility

• Because chlorinated hydrocarbons (DDT) are so persistent, they tend to show up far from the point of dispersal. Stored in fat bodies, and thus tend to

bioaccumulate.- High levels detected in upper levels of

food chain. DDT banned from US for over twenty

years, but high levels still detected in some areas.


Environmental Persistence and Mobility

• Many persistent organic pollutants were banned globally in 2001. Use was banned or restricted in

developing countries for years, but between 1994 and 1996, the US shipped more than 100,000 tons of DDT and POP’s annually.

- Many returned to US in agricultural products and migrating wildlife.


Human Health Problems

• WHO estimates between 3.5 and 5.0 million people suffer acute pesticide poisoning, and 20,000 die, each year. At least two-thirds resulting from

occupational hazards in developing countries.

Long-term health effects difficult to conclusively document.

- PCB’s have been linked to learning deficiencies in children.

Intake during mother’s pregnancy.


ALTERNATIVES TO PESTICIDE USE

• Behavioral Changes Crop Rotation Mechanical Cultivation Flooding Fields Habitat Diversification Growing in Pest-Free Zones Adjusting Planting Times Plant Mixed Polycultures


Alternatives to Pesticides

• Biological Controls Predatory / Herbivorous Insects Genetics and Bioengineering Hormones Sex Attractants


Integrated Pest Management

• Flexible, ecologically-based strategy that uses a combination of techniques applied at specific times aimed at specific pests. Tries to minimize use of chemical controls

and avoids broad spectrum controls. Employs economic thresholds to

determine the point at which potential economic damage justifies pest control expenditures.


REDUCING PESTICIDE EXPOSURE

• Less than 10% of active pesticide ingredients have been subjected to a full battery of chronic health-effect tests. Of the 321 pesticides screened, EPA

reports 146 are probable human carcinogens.

- Since 1972, only 40 pesticides have been banned.


Regulating Pesticides

• Environmental Protection Agency (EPA), Food and Drug Administration (FDA) and Department of Agriculture (USDA) all share federal responsibility for regulating pesticides used in food production in the US. EPA regulates sale and use, and sets

tolerance levels. FDA and USDA enforce pesticide use and

tolerance levels set by EPA.


Regulating Pesticides

• 1999, EPA banned use of methyl parathion on all fruit and many vegetables, and limited the quantity of azinphos methyl that can be used on foods common in children’s diets. Studies show children are more

susceptible than adults to toxic pesticides because they are still developing and have less natural protection.


Summary:

• Pests• Pesticides

Use and Types Benefits Problems Alternatives Reducing Exposure Regulating Use


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Cunningham - Cunningham - Saigo: Environmental Science 7 th Ed. Pest Control Chapter 12.

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