Diplodia Tip Blight
What is Diplodia Tip Blight?
Diplodia tip blight (formally known as Spheropsis) is caused by a fungal pathogen, Diplodia sapinea. Its characteristic black dots (the fungus’ fruiting bodies) are very easy to spot, peppering the cones on the ground as well as the needles and stems at the infection sites. The fungus spreads very rapidly under favorable conditions such as frequent rains and high humidity, which are perfect for disease development. It overwinters on last-year’s cones, on the bark, and on the tips of previously infected shoots. Spring rains and storms are responsible for releasing the spores and carrying them over long distances.
What does it look like?
If your landscape has Austrian pine and/or Scotch pine, chances are you have seen diplodia tip blight. It is characterized by unsightly brown, dead pine shoot tips that seem to appear overnight. Needles on the shoot tips start wilting, turn yellow and die. Those brown, dead needles are found mainly on the tips but can expand well below the tips down the branches. Eventually the entire branch dies. These dead patches are scattered throughout the tree. The wood appears to be dark brown or black.
Figure 1. New shoot die-back
Figure 2. Black fruiting bodies on last-year’s cones
What can be done about it?
The best way to avoid diplodia tip blight is to not plant Austrian and Scotch pines, as these species are very susceptible to the fungus. However, if these trees are already part of the landscape, you have several options for disease management. Sanitation is the first step in the war against this fungus. Prune out all the infected branches (during winter or dry periods), collect all the infected cones and dispose of them (do not compost them). To prevent infections, start an early spray program as the buds start to open. Apply fungicide sprays before rain events in order to protect the newly developing shoots. Product options include Daconil® (chlorothalonil), mancozeb, copper hydroxide, or thiophanate-methyl (Thiomyl, Cleary’s 3336™, Topsin® M). Before application, read and follow all label instructions.
Mirjana Bulatovic-Danilovich, WVU Extension Specialist, Consumer Horticulture – Agriculture & Natural Resources