Pesticides Chapter 15 Section 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 Control What 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 Control  Wild plants often have more protection from pests than crop plants. Why? Wild PlantsCrop 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 plants Evolved 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 Pesticides  Pesticide resistance  Human health impacts  Loss 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 pesticide to Kill 50% x to Kill 90% 10x to Kill 99% 100x to 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 Weeds  Why 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/yr There 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 Produce Highest Lowest Apples Asparagus Bell peppers Avocados Celery Bananas Cherries Broccoli Imported grapes Cauliflower Nectarines Corn (sweet corn) Peaches Kiwi Peas Mangos Potatoes Onions Red Raspberries Papayas Spinach Pineapple Strawberries 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