Browning and death of branch tips is quite common in older, well-established pine plantings. Austrian pine is the most severely affected, but this type of damage can also be found in Ponderosa, Scotch and Mugo pine.
The culprit is a fungal disease called Diplodia tip blight, (syn. Sphaeropsis tip blight). Infection kills current-year shoots and eventually may kill whole branches. This disease becomes increasingly common and destructive as trees age, although young trees can be affected.
Symptoms
The most conspicuous symptom of Diplodia tip blight is stunted new shoots with short, brown needles still partially encased in their sheath. Infected shoots are quickly killed and may be located anywhere in the tree's canopy, although damage is generally first evident and most severe in the lower branches. After two or three successive years of infection, tree tops may also be extensively damaged. Repeated infections reduce growth and deform trees. Branches that have been infected several years in a row often die back completely.
Small, black, pimple-like structures develop at the base of infected needles and on the backside of pinecone scales. These structures produce additional fungal spores that can re-infect the tree.
Pests Causing Similar Symptoms
Diplodia tip blight can be confused with pine tip moth damage, however, the larvae or tunnels will be found within shoots when they are slit open if these insects are causing the damage.
Damage should also not be confused with pine wilt, a diseased caused by trunk-dwelling nematodes, which is killing many pines across Nebraska. Pine wilt primarily affects Scotch pine trees, and kills the entire tree very quickly. Usually within a matter of 2 or 3 months.
Control
New shoots are most susceptible during a two-week period starting when the buds begin to open and continue to be susceptible through mid-June. Infections are worse during years with very wet spring conditions, which promotes disease infection. High humidity also promotes the germination of spores. Fungus spores are dispersed primarily on rain splash from March to October.
Two fungicide applications are recommended for control. For eastern Nebraska, the first application is usually made during the third week in April, and the second application in the first week of May. Watch your pine trees closely for the opening of buds at the tips of the branches, and time your first fungicide application accordingly.
Fungicides that are effective in treating this disease include propiconazol (Ferti-lome Systemic Fungicide), thiophanate-methyl (Cleary's 3336), and copper formulations such as liquid copper (Tenn-Cop 5E) or fixed copper (Basic copper sulfate, Tribasic copper sulfate).
The fungicide brand names listed above are examples of available products. Other formulations of these chemicals will also be effective in controlling this disease, and can be used as long as they are labeled for use on evergreen trees.
Always read and follow all label directions carefully before making any pesticide application.
Images and More information:
- Diseases of Evergreen Trees, Nebraska Forest Service
- Sphaeropsis Tip Blight of Pine, Nebraska Extension