Conidia, produced in sporodochia are wind disseminated primarily in the summer during wet periods. Occasionally deodar weevils, Pissoides nemorensis, which breed in dying trees and feed on phloem of healthy trees, transmit the pitch canker fungus. The pitch canker fungus grows readily in susceptible tissues causing the host to produce a number of characteristic symptoms. Initial yellowing of needles is quickly followed by bright reddish-brown discoloration. Dead needles may persist for more than a year, fading to a dull grayish-brown.
New growth developing from previous years infection rapidly wilts, turns brown, and dies.
Dieback of shoots of the current years growth is one of the first symptoms produced by infected trees. Terminals and upper laterals are most often affected. Wood beneath cankers becomes discolored and resin soaked. Characteristic signs include the presence of cushion-shaped, salmon to pink colored sporodochia in needle depressions on pine shoots and branches and bark surfaces. Microconidia and sickle-shaped macroconidia can be observed with the aid of a microscope.