Galls interfere with the natural formation of twigs and cause curling, stunting and the eventual death of new growth. Heavy infestations give the trees a ragged, unsightly appearance. Thus galls prevent twig growth and, if they are abundant, may affect entire trees. Individual trees vary in susceptibility to attack; some appear immune, others suffer growth reduction, and some are eventually killed. By itself, gall growth rarely causes lasting damage, but tends to leave affected trees susceptible to other health problems, including infestation of disease causing organisms and other harmful insects. Trees growing on good sites are generally less susceptible to attack than those on poor sites.
