Pesticides Science 10

Pest – is an organism that people consider harmful or inconvenient Pest – is an organism that people consider harmful or inconvenient –Examples: Weeds, insects, fungi, and rodents Weeds, insects, fungi, and rodents Pesticides are chemicals designed to kill pests. Pesticides are chemicals designed to kill pests. –Examples: Raid, DDT Raid, DDT Initially pesticides were created and used because of a huge loss in farmers crops.

Advantages of Using Pesticides 1. Kills bugs that eat crops or that hurt our pets 2. Keeps weeds out of crops 3. Kills bacteria or mildew that could make us sick

Disadvantages of Using Pesticides 1. Toxic effects on the body (carcinogenic) 2. Air and water pollution 3. Too much can be damaging to crops 4. Bugs can become resistant

What is the main difference between first generation and second generation pesticides? 1 st Generation – natural chemicals 1 st Generation – natural chemicals 2 nd Generation – made in Laboratory; fat soluble 2 nd Generation – made in Laboratory; fat soluble

TYPES OF PESTICIDES Type of Pesticide TargetPersistence InsecticideInsects 2-15 years HerbicideWeeds Days to Weeks FungicideFungi/Moulds Few Days BactericideBacteria RodenticideRodent Few days

1. The First Generation Pesticides – (Metallic based, ex. Lead, mercury and arsenic) Not only did they kill insects, they were highly poisonous for people.

DDT 2. The Second Generation Pesticides (Chemicals made in a lab ex. DDT) DDT is a potent insecticide made in At the time it was made people did not know it’s harmful effects At the time it was made people did not know it’s harmful effects (Effects: carcinogenic, thinning of egg shells, birth defects, etc. Debate is that it has a low toxicity towards animals and it will save millions in the wat against malaria) (Effects: carcinogenic, thinning of egg shells, birth defects, etc. Debate is that it has a low toxicity towards animals and it will save millions in the wat against malaria)

DDT con’t 2.3 million tonnes of DDT was used/year (peak usage was in 1962) 2.3 million tonnes of DDT was used/year (peak usage was in 1962) Today, there are 500 registered insecticides used in Canada Today, there are 500 registered insecticides used in Canada 75% of the banned insecticides are still used in 3 rd World Countries 75% of the banned insecticides are still used in 3 rd World Countries

Where do you get your bananas? See Table 1 Page 53 for various types of pesticides. Bioamplification Is the increasing concentration of a toxin, in the fatty tissue, as organisms consume each other. Is the increasing concentration of a toxin, in the fatty tissue, as organisms consume each other. Early pesticides were fat-soluble which means they would stay in the body. For example: If a grassland ecosystem was sprayed with DDT, the fat-soluble pesticides would stay in the herbivores body, and the carnivores body, etc… As the chemical accumulates so does the toxic effect. Early pesticides were fat-soluble which means they would stay in the body. For example: If a grassland ecosystem was sprayed with DDT, the fat-soluble pesticides would stay in the herbivores body, and the carnivores body, etc… As the chemical accumulates so does the toxic effect.

The concentration of fat-soluble pesticide increases as you move up the food chain.

BIOAMPLIFICATION: PREVENTION Make pesticides that do not stay in the fat tissue Make pesticides that do not stay in the fat tissue Make pesticides that can be extracted from your body thru urination. Make pesticides that can be extracted from your body thru urination.

3. Modern Day Pesticides – Water Soluble Because they are water soluble they will not stay in the body Because they are water soluble they will not stay in the body They can be excreted through sweat and urine and are easily broken down in the soil. They can be excreted through sweat and urine and are easily broken down in the soil. Problems: need to be reapplied frequently because they break down so quickly, they are only effective for short periods of time, cost for reapplication. Problems: need to be reapplied frequently because they break down so quickly, they are only effective for short periods of time, cost for reapplication.

Where Do Pesticides Come From? 1. Plants Nicotine comes from tobacco plants.Nicotine comes from tobacco plants. It is used to kill insects. It is used to kill insects. 2. Shells of diatoms (tiny organisms that live in water) They are crushed into a powder and used to kill fleasThey are crushed into a powder and used to kill fleas 3. Chemicals made in a lab or factory They are made into liquids to be sprayed onto the pest.They are made into liquids to be sprayed onto the pest.