a disease of Pinus ponderosa and related species —note 1. limb rust is caused by a group of fungi with poorly understood taxonomy including Peridermium filamentosum, Cronartium arizonicum, C. coleosporioides, and probably other taxa —note 2. known alternate hosts of limb rusts are in the figwort family (Scrophulariaceae), which kill branches in the crown without girdling the tree; tree mortality occurs when the crown can no longer sustain the tree or when the weakened tree is attacked by bark beetlesThis definition last updated 07/12/2008