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.