Yesterday I spoke with members of the IAA at their summer conference. I was invited to host a short workshop involving diagnostics for trees, and I choose to focus on diplodia tip blight in pines. I specifically talked about characteristic symptoms and signs you can use in the field to feel confident in a diagnosis of diplodia on pine. It was a lot of fun and I really enjoyed meeting people who are passionate about their trees and talking with them about tree health.
Diplodia is one of the more common causes of pine needle diseases in Illinois, but it can affect other hosts as well. Earlier this week I was working with a holly sample with brown leaves that were dying, and it looked like a generalized dieback. Generalized decline is usually due to something wrong with the roots or the vascular system; for whatever reason, the flow of water and nutrients within the plant is being interrupted.
Holly get a number of cankers, so I examined the branches and found small fungal fruiting structures. I made a slide and took a look under the compound scope and found an old familiar friend: diplodia! Apparently diplodia cankers on holly are not uncommon, but we tend to see other canker-causing fungi on holly in Illinois more frequently. This was my first time seeing diplodia on holly, and any time I see a new disease I get a little excited (and apparently the fungal gods approved of my topic for the IAA workshop).