are caused by the piercing and sucking action of hemipterans and mites. Usually these animals inject saliva for the external digestion of the plant juices prior to their ingestion. The toxic effect of the saliva results in small, circular ‘dead’ spots on the leaf.

are the abnormal, tumour-like growth of plant tissue. Depending on the affected plant tissue we talk about leaf, flower, fruit, stem, shoot, petiole galls, etc. Galls are either induced by the saliva injected during the piercing-sucking action of Hemiptera and mites or galls are caused by gall-forming insects that lay their eggs into particular plant tissue. The immature stages of these gall-forming insects develop and feed inside their gall.