HOW ARE GALLS FORMED?
Galls are natural plant products. Either mechanical damage or salivary secretions (introduced by immature insects and mites) initiate production of normal plant growth hormones. These plant hormones cause localized plant growth that can result in increases in cell size (hypertrophy) and/or number (hyperplasia). The outcome is an abnormal plant structure called a gall. Gall formation usually occurs during times of fast growth (late spring) of new leaves, shoots, flowers, etc. The gall making organism develops inside the gall and the gall continues to grow as the insect/ mite feeds and matures. Mature plant tissues are usually unaffected by gall inducing organisms. A variety of organisms are capable of initiating galls. The most common are: eriophyid mites; gall midges (cecidomyiid flies); gall wasps (cynipid wasps); aphids (plant ice); and psyllids (jumping plant ice). Although many species of plants are attacked, oak (Quercus spp.) is by far the most commonly affected (over 800 known g
