Green scale: a pest of coffee

Abstract

Green scales are insects which feed on coffee and other plants in many parts of Papua New Guinea. They feed by sucking the sap of the plants through special mouthparts and they excrete a sweet sticky substance called honeydew. Ants look after the green scales because they like to feed on the honeydew. Also a fungus called sooty mould grows on the honeydew. Both the green scales and the sooty mould
cause the growth of the plant to slow down. Because of this, green scales are considered to be a very serious pest of coffee in Papua New Guinea.