Diseases of Conifers

Coniferous forests carry their own unique threats, including both native and nonnative diseases. Many of these diseases have been present in the United States for decades and have played a vital role in shaping forest structure. They generally attack individual weakened or severely stressed trees, often following insect invasions. Overall, their action served to thin forests, reducing competition, leaving the stronger trees, and decreasing the risk of severe outbreaks.

It is important to understand the physiology and history of these conifer and hardwood diseases to inact proper management when infestations occur. For example, annosus root disease enters freshly cut pine stumps, thus being problematic on pine plantations. However, littleleaf disease is often not a problem on plantations with short rotations since intensively managed stands are regenerated before losses become serious. The development of genetic resistance in planting stock has been, or has potential to be, a major disease management strategy for fusiform rust, brown spot needle, and pitch cankers. Knowledge of these and other differences are both interesting and imperative in understanding severity and urgency when dealing with insect infestations.

In this section, more detail is provided about 5 diseases, including fusiform rust, annosus root disease, brown spot needle, littleleaf disease, and pitch cankers.