Abstract:
Most weeds or insect pests that appear suddenly originate from other countries. These being their native home, they normally have natural enemies that evolve with them and help to keep those plants or insects to a very low population level. Once such a plant or insect, free from competition with its native neighbors and without its native natural enemies, appears in virgin land, the population density increases very rapidly. Such an insect or weed is referred to as EXOTIC. Examples of exotic weeds are Lantana camara and water hyacinth while exotic insect pests in Uganda include the cassava mealybug and cassava green mite.