Silent Spring Chapters 7 & 8 Christopher Siess, Jaclynn Chen, Catherine Flynn

Pests  According to Charles Eton, the key to a healthy community lies in keeping “the conservation of variety.”  This variety keeps any one species from dominating over the others and becoming a pest.  We learned in the textbook that an organism’s success in a new environment is dependent on : predation, disease, competition, and absence of certain species.  The Japanese beetle thrived in the United States because the U.S. lacked any species that would prey or compete with it.  Once organisms such as the parasitic wasp Tiphia vernalis were introduced into the U.S., they controlled the Japanese beetle.

Pests  Birds such as the woodpecker are natural controllers of potential pests such as the Engelman spruce beetle. Once these birds die as a result of insecticide poisoning, there is no natural protection left to keep the pests in check.  The Ten’s Rule- an average of one out of ten introduced species become established, and one out of ten established become common enough to become pests.

Pesticides  Detrimental insect poisons, pesticides, have wreaked needless havoc in the environment harming numerous species throughout the community.  Although a single spray will temporary reduce numbers of pests, they will return, and a new spraying campaign must take place.

Pesticides  Pesticides used unwisely can cause immense collateral damage.  In the fall of 1959, 27,000 acres of land in southern Michigan was sprayed, its purpose to control the Japanese beetle population.  What happened was a sharp increase in respiratory and nervous conditions, and scourging of the bird and house pet populations.

Pesticides  One of the reasons birds and other species were eradicated was because of direct contact. The birds came into contact with the poison when it was dispersed.  Another reason was because of the food chain. When infected beetles came to the surface for their last hours, the birds ate these easy pickings and became infected.

Pesticides  A DDT spreading affected a flock of sheep. In a short time, the sheep experienced “symptoms of intoxications almost at once…lost interest in food, great desire for water, displaying extreme restlessness, following pasture fence apparently searching for way out…” (Carson 94)

Abiotic Factors to Distribution Restriction Abiotic Factors TemperatureWaterSunlightRocks & SoilWind

Chain of Infection Dutch Elm Disease Introduced in the 1930’s Is a fungus that spreads spores that kills Elm trees Spread by elm bark beetles Attempted eradication by pesticides Collects on tree leaves Decomposes in soilEaten by earthworms Eaten by Robins 90% Robin Population Decrease Eaten by Possums, Squirrels, etc

Governmental Interference  Government officials on many levels insist that the plainly dangerous poisons were completely safe to all untargeted species.  Budget concerns demanded the use of less-safe poisons for less expense.

Since Then  Public attention to pesticide spraying has increased, as had the demand of the introduction of natural predators instead of poisons.  If a natural predator is determined to not cause as much havoc as the pest that was introduced, it shall be attempted to be established.