James A. Chatfield, Ohio State University Extension, Northeast District/Horticulture and Crop Science; Nancy A. Taylor, Plant Pathology, C. Wayne Ellett Plant and Pest Diagnostic Clinic, Ohio State University; Erik A. Draper, Ohio State University Extension, Geauga County; and Joseph F. Boggs, Ohio State University Extension, Hamilton County/Southwest District.
Nancy Taylor, director of the Ohio State University C. Wayne Ellett Plant and Pest Diagnostic Clinic, reminds sample senders that when you send pine and spruce samples to the clinic to check for needle diseases, please keep a couple of sample pointers in mind.
You should include not only branches with the discolored needles attached, but also a bag of fallen needles collected from branch crotches (rather than from the ground). This is because many needle diseases involve fungal infections of last season's needles. Examples include Rhizosphaera on spruce, Dothistroma on Austrian pine, and Lophodermium and Cycloneusma on Scots pine. Needles just starting to show symptoms are often quite difficult or impossible to diagnose properly.
Why does all this matter isn't a needle disease by any other name just a needle disease? No! Control recommendations may differ significantly. For example, on Scots pine, protectant fungicides for Cycloneusma needlecast should be applied to prevent infections in spring, but for Lophodermium needlecast, fungicides should be applied to prevent infections in late summer.
So, the correct diagnosis of which disease is on your pines is critical and to do this properly, collect older, fallen needles that have not yet dropped to the ground.