Although occasional outbreaks appear quite dramatic, long-term
damage from conifer needle diseases in the Southwestern Region is
usually minor. Sporulation, spread, and infection by these fungi
are frequently restricted to a specific season, depending on the
pathogen, and successful infection depends on favorable weather
conditions. Needle diseases are often more pronounced on younger
trees and the lower crowns of large trees, due to more humid conditions
favorable to disease fungi.
Figure 183. Conifer needle diseases are most noticeable in the spring before bud break.