PesticidesChapter 15Section 2

AIM Explain the benefits and environmental

impacts of pesticide use

DO NOW

In your EcoLog, discuss at least 2 negative impacts of pesticides

Pest Control-In North America, insects eat about 13%

of all crops-Crops in tropical climates suffer even

greater insect damage because the insects grow and reproduce faster in these climates.

-Worldwide, pests destroy about 33% of the world’s potential food harvest

Pest ControlWhat is a pest?-A pest is any organism that occurs where

it is not wanted or that occurs in large enough numbers to cause economic damage

-Pests can include plants, fungi, and microorganisms

Pest ControlWild plants often have more protection

from pests than crop plants. Why?

Wild Plants Crop Plants

Grow throughout a landscape, so pests have a harder time finding and feeding on a specific plant

Usually grown together in large fields, which provides pests with a one-stop source of food

A variety of pest predators live on or near the plantsEvolved defenses

Pesticides-Pesticides are chemicals used to kill

insects, weeds, and other crop pests-During the last 50 years, scientists

have invented many new pesticides.

Why? Pesticides were extremely effective – some pests have developed a resistance to pesticides therefore new pesticides needed to be developed

Pesticides-Pesticides can harm beneficial plants

and insects, wildlife, and even people

Impacts of PesticidesPesticide resistanceHuman health impactsLoss of biodiversity in the fields:

pesticides kill both target and non-target species

Loss of biodiversity higher up the food chain due to bio-magnification

Pesticide Resistance

-resistance = the ability to survive exposure to a particular pesticide

-more than 500 species of insects have

developed resistance to pesticides since the 1940s

Pesticide Resistance leads to Pesticide Treadmill

Increase tolerance, increase in resistance

What does this mean?

Need this amount of pesticideto Kill 50% x to Kill 90% 10xto Kill 99% 100xto Kill 99.9% 1000x

- hardiest ones live- next generations – very resistant- increase dosage or find new pesticide - time-consuming- costly

Heavy Reliance on Chemical Pesticides to Control Pests and WeedsWhy is this not sustainable?

Pesticide resistance results in a pesticide treadmill

Initial applications of a pesticide may kill 99.9% of the target insect, but the 0.1% left behind will be resistant to the pesticide and their genes will be passed on to each new generation of pest

Very short life spans for crop pests mean that in a short time pesticides will begin to lose their effectiveness (treadmill)

Health Effects of Pesticides

Reported US poisonings: 20,000/yr (est 1% world total)Reported US fatalities: 50/yrThere are > 25,000 brands pesticides registered in US

alone

Acute impacts Wheezing, respiratory distress Diarrhea, nausea, vomiting Blurred vision, salivation, seizures, coma, death

Chronic impacts Neurological effects Cancer (esp childhood cancers) Reproductive and developmental toxicity Endocrine disruption

Human Impacts from Chronic Exposure

95% of reported pesticide exposure cases occur in developing

countries, only acute cases

Reported cases in US typically only include acute poisonings, so

numbers relatively low

Human Health Concerns Pesticides are designed to kill organisms, so

they may also be dangerous to humans High cancer rates and nervous system

disorders Accidental chemical leaks

Endosulfan Cotton, potatoes,

apples, and tomatoes

CA = extinction of mountain yellow-legged frog

FL = contamination of Everglades

Stockholm Convention

Pesticides in ProduceHighest LowestApples Asparagus

Bell peppers AvocadosCelery BananasCherries BroccoliImported grapes CauliflowerNectarines Corn (sweet corn)Peaches KiwiPeas MangosPotatoes OnionsRed Raspberries PapayasSpinach PineappleStrawberries Peas (sweet)

Released 10/21/2003 by EWG

Pesticides and Human Impact

CLOSURE How would you suggest preventing

contamination from pesticides on food?

Michael Pollan Food Fight MOVIE - Ingredients

What have we done to reduce our dependence on pesticides? Biological Pest Controls Genetic Engineering

Pesticides and Biodiversity