Pine-pine gall rust

Habitat

Damp surfaces on these pine trees provide an environment conducive to spore germination; these surfaces are usually found on very young tissue of the current season's growth. The proper conditions must persist for at least 24 hours after the spore lands on its host in order to allow enough time for germination, penetration of host defenses, and establishment of the fungus. Environmental conditions conducive to infection typically occur during spring and early summer when weather is consistently cool and moist. Because of the very specific conditions required for spore germination and infection, pine-pine gall rust may not be observed in consecutive years as it is unlikely that optimal weather conditions and susceptible host tissue are both present at the time of spore release. Furthermore, infection severity is not uniform year after year. Only minor infections occur in an ordinary year, however infection may be prolific in certain years if the proper conditions occur. These years of abundant infection are termed "wave years" and are characterized by consistent cool, wet conditions and the increased local sporulation E. harknessii. Favorable conditions for large outbreaks of pine-pine gall rust do not occur often, but when they do they can affect areas as large as an entire state. Localized outbreaks are much more common, occurring in dense even-aged stands.