Diplodia Tip (Shoot) Blight

Diplodia Tip blight (Diplodia spp.) is a common fungal disease in Wisconsin, that predominately affects 2-3 needle pine trees.  Austrian and Scots pine may be the most susceptible, but Mugo and Red pines are also affected.  In some cases, Diplodia is also found on spruce, fir, and other coniferous species.  It is an opportunistic disease that often infects trees under drought or construction stress, insect attack (Zimmerman pine moth, etc.) or with some other predisposing factor.  This is especially true with Austrian pine, a tree that is not well suited for planting in our area.

Signs & Symptoms of Diplodia Blight

As the name suggests, this disease causes a tip blight, causing dieback of new growth and branch tips.  When severe this dieback can be quite noticeable and, as the disease progresses, fungal cankers may form and spread into the twigs, limbs, and can eventually reach the main trunk. 

Diplodia Blight Life Cycle

Diplodia forms fungal fruiting bodies, which release spores, on diseased twigs and on pine cones (2nd year) and new infections primarily occur during times of wet weather (spring, and other wet periods through fall).  Rain, wind, and other vectors (such as insects, wildlife) can all spread the fungus.  New growth in spring is highly susceptible and a way the fungus can cause new infections, but the disease can also enter the tree via new wounds caused by hail, mechanical, or other methods.

Managing Diplodia Blight

The best management is to be proactive and avoid tree stress!  Irrigation during times of drought, mulching, and prescription fertilization all go a long way (note:  avoid high nitrogen fertilizers, as these can actually promote susceptibility).    When planting, avoid Austrian Pine and select sites that will allow for proper establishment.  Once infected, fungicide sprays and other means to promote tree health may be recommended.  3 fungicide sprays during spring, beginning at “bud break” and continuing through shoot elongation, will help prevent infections of new growth.  Application of growth regulators can also be of value, as these can increase overall tree health, promote drought resistance, and increase defense compound production.  If compaction or insect infestation are also present, Air-spade soil de-compaction and insect control may also be recommended for your tree.