Studies on the Damage and Control of Psylla chinesis

The damage and control of Psylla chinesis were studied from 1987 to 1991.The results were as follows:The pear psyllid is one of the main pests of pear trees.They feed on the leaves in concealment.Under serious condition,they can make the leaves fall earlier.The tolerable pest density is 3 on a leaf base and 10 on a leaf blade.This is regared as the threshold,under which the pests don't cause serious damage.The control threshold for the numph is 0.4 on a leaf blade in the whole pear orchard.The field of the orchard should be irrigated at severe winter.The first-generation nymphs must be controlled.The time for control is determined by control threshold.These methods are effective and have achieved better economic benefit.