Academic journal article The Science Teacher

The Green Room

Academic journal article The Science Teacher

The Green Room

Article excerpt

Pests and Pesticides

As prime gardening season arrives, many of us go to combat with garden pests. Aphids, slugs, tomato hornworms--all have attacked my garden. So, what is a pest? Agricultural pests are any undesirable organisms that compete with us for the food plants we grow or harm those plants in some way. Insects enjoying our newly planted vegetable gardens come to mind, but weeds also compete with the plants we try to grow. Weeds cause some $15 billion in losses to farms in the United States each year (Bridges 1994).

In complex, diverse, natural ecosystems, most pest species are controlled by their natural enemies--predators and parasites. Unfortunately, this natural pest control is less effective in the more simplified ecosystems of farms. For example, numerous species of lady beetles prey upon aphids (Charlet, Olson, and Glogoza 2002), but most farms do not provide the variety of resources these predators need to thrive. Lacking natural pest control, U.S. farmers often turn to pesticides to control pests and minimize their crop losses.

The first pesticides were broad-spectrum inorganic toxins, such as compounds of arsenic. These widely toxic poisons, such as lead arsenate (used against the potato beetle), were eventually replaced by botanical (plant-based) pesticides, such as nicotine sulfate, a compound produced by tobacco plants. These pesticides were natural, biodegradable substances. Pesticides made from synthetic organic compounds came in the late 1930s with the introduction of dichlorodiphenyltrichloroethane. DDT was developed to combat insect-borne human diseases such as malaria and control insect pests in agriculture but came under regulation in the United States when its negative environmental effects became clear in the 1960s (see "On the web"). In general, these pesticides are effective pest killers and many, such as atrazine (a herbicide), are still heavily used in U.S. agriculture.

According to the U.S. Environmental Protection Agency (EPA), over one billion pounds of pesticides are used annually in the United States, with 80% of that used in agriculture. Get a complete history of pesticide use on the EPA's general pesticide information pages (see "On the web").

Classroom activities

Start with an activity provided by the Prince Edward Island department of education. Students read a brief article to get an overview of the environmental, economic, and societal impacts of pesticides and the role of synthetic chemicals in agriculture. …

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