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Pests & Bioamplification

Foodwebs in Grassland vs. Potato Field


Pests & Bioamplification

Foodwebs in Grassland vs. Potato Field


Pests & Bioamplification

Foodwebs in Grassland vs. Potato Field


Pests & Bioamplification

Pesticide: a substance used to kill a pest

herbicides kill plants

insecticides kill insects

fungicides kill mouldsetc


Pests & Bioamplification

Pesticide: a substance used to kill a pest

herbicides kill plants

insecticides kill insects

fungicides kill mouldsetc

Broad-spectrum pesticide: effective against many types of pests

e.g. DDT is toxic to most insect species

Narrow-spectrum pesticide: effective against only a few types of pests

e.g. Bt, a modern pesticide from bacteria is toxic only to caterpillars


Pests & Bioamplification

How pesticides work:

1. Physical harm: diatomaceous earth scratches the waxy outer coating of insects so they dehydrate


Pests & Bioamplification

How pesticides work:

1. Physical harm: diatomaceous earth scratches the waxy outer coating of insects so they dehydrate

2. Biological harm: some herbicides interfere with photosynthesis


Pests & Bioamplification

Issues with pesticides:

1. Non-target species: pesticides often kill species they were not intended to kill

e.g. a broad-spectrum insecticide may kill predatory insects that normally feed on pests


Pests & Bioamplification

Issues with pesticides:

1. Non-target species: pesticides often kill species they were not intended to kill

e.g. a broad-spectrum insecticide may kill predatory insects that normally feed on pests

2. Bioaccumulation: the increasing concentration of a pesticide as it moves up the food chain

e.g. DDT is a long-lasting insecticide that wiped out song bird populations in the 1960s


Pests & Bioamplification

Bioaccumulation:

e.g. DDT leached into a lake from fields

herring gull egg (6.3 ppm)

smelt (0.43 ppm)

(fish)

freshwater shrimp (0.03 ppm)

ppm = parts per million


Pests & Bioamplification

Persistent chemicals: the bioaccumulation occurred because these pesticides lasted a long time in the environment and could be passed up the food chain

-today pesticides are developed to break down quickly to avoid this buildup


Pests & Bioamplification

Pesticide Resistance: when a species targeted by a pesticide are no longer affected by it.

-happens by chance mutations of DNA

-once it occurs, these individuals with resistance produce the most offspring and the resistance quickly spreads to the entire species

-the more frequently the pest reproduces, the faster resistance will develop


Pests & Bioamplification

Organic Farming:the system of agriculture that relies on non-synthetic pesticides and fertilizers

Integrated Pest Management: a system that uses a combination of physical, chemical, and biological controls


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