Safe food handling refrigeration freezing and canning prevent spread of disease

Safe food handling refrigeration freezing and canning

This preview shows page 7 - 10 out of 14 pages.

Safe food handling, refrigeration, freezing, and canning prevent spread of disease and rotting Catastrophes increase diseases, sickness, death
Control by natural enemies There are four types of natural enemies: Predators, parasitoids, pathogens, herbivores Predator beetles prevent the non-native wooly adelgid from killing hemlock trees Mealy bugs and caterpillars in Africa are controlled by parasitic wasps “Green muscle” (a fungus) controls desert locusts Brazilian weevils control water hyacinth in lakes Over 30 weed species are limited by insects - Parasitic wasps use moth caterpillars as their hosts Protect the natives Natural enemies must control the target species without attacking desirable species 1% of 50,000 plant-eating insect species are pests The other 99% are controlled by natural enemies Conservation : protect natural enemies already here The first step in using natural enemies for control Avoid or restrict broad-spectrum chemical insecticides These natural enemies control secondary pests (which become pests only after using pesticides) Import aliens as a last resort Effective natural enemies are not always available We import pests, but not their enemies Natural enemies are found in the pest’s native land They must be carefully tested before being released Introduced species can be a success or failure Cane toads, imported to control beetles, overran Australia’s natives instead But a parasitoid wasp has successfully controlled the cassava mealybug in Africa Better science and controls help releases succeed Cane toads and Hessian flies Cane toads, introduced to Australia to control beetles in sugar cane fields, became pests themselves Plant breeding Most insects and plant pathogens attack only one or a few closely related species Incompatible plants are not attacked Genetic control strategies: develop genetic traits in the host species that provide incompatibility The hosts are resistant to attack by the pest But scientists and disease continue to battle Scientists developed wheat resistant to wheat stem rust, a parasitic fungus A new fungus is now spreading to Asia, devastating wheat Control with chemical and physical barriers Plants can produce substances that are lethal or repulsive to the pest A wheat variety produces a chemical that kills the larvae of the Hessian fly Losses to this pest are less than 1% of the non-resistant wheat varieties
Plants can have physical traits that trap pests Leaves with hooked hairs trap and hold immature leafhoppers until they die Glandular hairs that secrete a sticky substance trap other pests Chemical and physical control of plants A wheat plant produces a chemical toxic to Hessian flies, while sticky hairs on this alfalfa plant trap an immature leafhopper Biotechnology and Bacillus thuringiensis Incorporating the protein coat of a virus into the plant The plant becomes resistant to the viral infection

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture