Protecting Food Resources:

Pesticides and Pest Control

Pesticides: Types and Uses

What is a Pest?– A pest is any species that competes with us

for food, invades lawns and gardens, destroys wood in houses, spreads disease, or is simply a nuisance

• Most of the time nature takes care of the pests through natural enemies (predators, parasites, and disease organisms)

So what’s a Pesticide?

• Pesticides (also known as biocides) are chemicals that are to kill organisms we consider undesirableex. – insecticides, herbicides, fungicides,

nematocides, and rodenticides

Above: Worker prepares his vehicle for a day of pesticide spraying

Coevolution

For almost 225 million years, plants have been producing chemicals to ward off or poison herbivores that feed on them…

But, through what is known as coevolution, the predators overcome various plant defenses by natural selection and the plants must develop new defenses

First Attempts at Pesticides

• Sulfur (early 500 BC)

• Toxic compounds of arsenic, lead, and mercury (1400’s)– Abandoned in late 1920’s when the increasing

number of human poisonings increased

• Nicotine Sulfate (1600’s)

• Pyrethrum and Rotenone (mid-1800’s)

Paul Mueller and the Second Generation

In 1939 Paul Mueller discovered that DDT, a chemical known since 1874, was in fact a potent insecticide. DDT became the first pesticide of the so-called Second Generation Pesticides. Mueller went on to win the Nobel Prize in 1948 for his discovery.

Pesticides Today

• Chemists have been developing hundreds of synthetic organic chemicals for use as pesticides

• Worldwide about 2.3 million metric tons of pesticides are used yearly– 1 lb for each person on earth– 75% in developed countries (Latin America,

Asia and Africa on the rise)– 1996 world sales = $30 billion($11 billion: US)

Spray those fields

Here in the US

• About 630 different biologically active (pest killing) ingredients and about 1,820 inert (inactive) ingredients are mixed to make some 25,000 different pesticide products in the United States

Pesticide Distribution in US

• Cultivation of two crops – Cotton (55%)– Corn (35%)

• Used about 90% of the insecticides and 80% of the herbicides applied to crops in the United States in 1995

Example of Solid Pesticides

More Distribution

• 25% of the pesticide use in the United States is for ridding houses, gardens, lawns, parks, playing fields, swimming pools, and golf courses of unwanted pests

• Average lawn in US = 10x’s more pesticides per hectare than US cropland

• Each year = 250,000 residents become ill

Some Quick Facts

• Broad-Spectrum agents : toxic to many species

• Selective or Narrow spectrum agents : effective against a narrowly defined group of organisms

• Pesticides vary in persistence (length of time they remain deadly in environment)

The Pros

• Pesticides save human lives: has prevented premature births due to malaria, bubonic plague, typhus, sleeping sickness (all carried by pests)

• Pesticides increase food supplies and lower food costs: 55% of crop lost before harvest due to pests

• Pesticides increase profits for farmers: every $1 spent on pesticides yields worth approximately $4 (although dropped to $2 if harmful effects)

Farmers in all countries have tried pesticides to save there crops

More Pros

• Pesticides work faster and better than alternatives: Pesticides can control pests quickly and at a reasonable cost. Long shelf life and easily shipped and applied

• Health risks insignificant when compared to their benefits– Safer more effective pesticides are being developed

• New pesticides are being used in less rates per unit when compared to older products

Ultimate Goal of Pesticides

• Kill only the target pest

• Harm no other species

• Disappear or break down into something harmless after doing its job

• Not cause genetic resistance in target

• Be cheaper than doing nothing

The Cons

• Genetic Resistance: pest organisms develop resistance to the pesticide after a short period of being exposed to it

• Broad-Spectrum insecticides kill natural predators and parasites that may have been maintaining the population of a pest species at a reasonable level– Ex. Wolf spiders, wasps, predatory beetles…

Cons continued…

• Because natural predators can be wiped out; this may unleash new pests whose populations the predators had previously held in check

In Our Water

• Testing in rivers and water reveal that pesticides have strayed away from there targets and found there way into the waters

Pesticide Treadmill

• As pests become resistant to the pesticides, sales reps for the pesticide recommend larger doses or more frequent application– As a result farmers end up on a pesticide

treadmill where they end up paying more and more for a pest control program that often becomes less and less effective

Example of Pesticide Treadmill

In Central America, cotton growers increased the frequency of insecticide applications from 10 to 40 times per growing season. Still, declining yields and falling profits forced many of the farmers into bankruptcy

Where does it all go?

• Only about 2% of the sprayed insecticide by air reaches target pests

• Less than 5% of herbicides applied reach target weed

• Pesticides that don’t reach there target end up in the air, surface water, groundwater, bottom sediments, food and other nontarget organisms

Continued

• Still, pesticide waste can be reduced by using recirculating sprayers, covering spray booms, and using rope-wick applicators

DDT

• Banned in 1972 by US

• 1980 high levels in peregrine falcon and the osprey

• EPA found DDT in 99% of the freshwater fish it tested

• DDT drifts from other countries still using it

Checking for pesticide residue in food

Regulation in the US

• All commercial pesticides must be approved by EPA

• EPA reviews each pesticide• EPA sets tolerance levels : amount of toxic

pesticide residue that can legally remain on crop

• No longer has to test on birds and fish • 55 active pesticides banned in US, but

may be used and shipped elsewhere

More Regulations

• National Academy of Sciences says that the federal laws are not adequate

• 98% of potential risk of cancer would be eliminated if pesticide residue on food eliminated by government

• Approximately $1 Billion spent on regulating pesticides each year

1996 Food Quality Protection Act

• Requires food to have only reasonable levels of pesticide tolerance

• It requires manufacturers to demonstrate that the active ingredients in there products are safe for infants and children

• Requires EPA to consider exposure to more than one pesticide when setting pesticide tolerance levels

• EPA develops program to screen ingredients

From Above

• Just one of the many ways that pesticides are being applied are through aerial drops of the chemicals

Other Solutions

• Crop rotations

• Planting times can be adjusted

• Plowing at night (reduces weeds)

• Plant where major pests do not exist

• Switch away from monoculture to intercropping, agroforestry, and polyculture

More Solutions

• Plants and animals that are genetically resistant to certain pest insects, fungi and diseases can be developed

- downside: costly• Biological control: predators and pathogens • 300 biological pest control successful in China

and Cuba• Biological Control: non-toxic to humans

– Downside: timely

Pesticides are plentiful as seen here and it comes in many different forms

Even more Solutions…

• Plant toxins– Bt toxin used to kill thousands of strain of

common soil bacterium

• Insect Birth Control (sterile male approach)

• Aqua heat: spray boiling water on crops

Yes… more solutions

• Some crops can be exposed to gamma rays after harvest– Extends shelf life– Critics say irradiating food destroys vitamins

and other nutrients– Increases death from botulism poisoning– Picowaved stickers on food that has been

IPM

• Integrated Pest Management

• Goal is reduction of crop damage t an economically tolerable level– Carefully monitor damage levels of pests

• When reached, farmers first use biological methods

• Small amounts of insecticides are used as a last resort

Pesticides in Politics

• Pesticides have been a big issue with environmentally safe activists. It is a big topic the EPA has to deal with