Nematodes are a large group of unsegmented worms that can be plant parasites. Snails and slugs are mollusks that prefer cool, moist surroundings. They include fish, amphibians, reptiles, birds and mammals. Most of our concern is with birds and mammals. Rodents are mammals that interfere with people, or cause harm to crops and livestock.
Disease agents cause diseases in plants and animals.
Many of these organisms are submicroscopic, making identification difficult. If you can't see the pest, then it may be identified by the type of symptoms caused or damage done to their host animals or plants. Each of these will be studied in more detail in the Plant and Soil Science Advanced Occupational Cluster. C. Growers throughout the world must compete with weeds, insects, plant parasites, birds and rodents. The energy, time and expense used to combat these problems stagger the imagination.