Galls or plant galls are abnormal outgrowths of plant tissues and can be caused by various parasites, from fungi and bacteria, to insects and mites. Galls are often very organised structures and because of this, the cause of the gall can often be determined without the actual agent being identified. This applies particularly to some insect and mite galls. Causes of plant galls Insects Insect galls develop under the influence of gall-inducing insects. Insect galls are usually induced by the chem… (More on Gall)