Antibiosis: A natural association between organisms that is detrimental to at least one of them. This often refers to the production of chemicals by one microorganism that is harmful to another.Biological Control Agents: Organisms, biological agents, or biologically-derived agents used strategically for their positive or adverse effect on the physiology and/or reproductive health of other organisms.Pantoea: A genus of gram-negative, facultatively anaerobic, straight rods which are motile by peritrichous flagella. Most strains produce a yellow pigment. This organism is isolated from plant surfaces, seeds, soil, and water, as well as from animals and human wounds, blood, and urine. (From Bergey's Manual of Determinative Bacteriology, 9th ed)Plasmodiophorida: A group of EUKARYOTES that are parasites of plants. Life cycle stages include zoospores and plasmodia.Aphids: A family (Aphididae) of small insects, in the suborder Sternorrhyncha, that suck the juices of plants. Important genera include Schizaphis and Myzus. The latter is known to carry more than 100 virus diseases between plants.Erwinia amylovora: A species of gram-negative bacteria, in the genus ERWINIA, causing a necrotic disease of plants.Plant Diseases: Diseases of plants.Pythium: A genus of destructive root-parasitic OOMYCETES in the family Pythiaceae, order Peronosporales, commonly found in cultivated soils all over the world. Differentiation of zoospores takes place in a vesicle.Pest Control, Biological: Use of naturally-occuring or genetically-engineered organisms to reduce or eliminate populations of pests.