Is needle cast a general term for several kinds of different fungus issues?If it was important to diagnose accurately, one would like to know the pattern of distribution of the browning in the crown (top to bottom? bottom to top? outside to inside?) and on the individual branch (older needles first?). A close look with a magnifying glass: are there itty-bitty black dots? Are they in single or double file? Are they on the upper or lower needle surface? On needles that are part green and part brown, any color gradations between the live and the dead parts? Yellow, purple, orange?
I realize that odds are, calling it "needle cast" and leaving it at that would be fine. Some readers here want to know more than a label for a condition and want to know "what should I look for ?" using available tools.
I could send you some PPTs on pests and diseases if you would like.Slight derail, but related: Besides the obvious silk on the needles, how can you tell if it’s mite damage or a needlecast/similar disease? Diseases and fungi are one big area where my knowledge is very limited.
We have a lot of declining and just plain dead Spruce around here, and we have had Spruce Spider Mite problems the last couple Springs, but I am sure that’s not the only cause of the demise of all these trees.
I believe it does hold true but differences of symptoms between spruce species is for sure a reality. Rhizo on a blue spruce is pretty different in appearance than how it looks on say a Norway spruce.Ah, much better with respect to DeeGore images. Yes, needlecast fungi are present!
First thing: those white dots are the stomates (or stomata for those who prefer). Those are the breathing pores that allow for gas exchange in photosynthesis (and I think for respiration as well). The needlecast fungi generally fruit on or through the stomata, so that is why the black dots are pretty orderly.
I don't think I saw which spruce species was sampled and where it's located, and that could affect diagnosis of causal agent. At least for blue spruce, Rhizosphaeria will fruit on dead parts of needles. As the provided sample images show black dots on green needles, that shifts the call to Stigmina. JD, does that hold true for other spruce species?
I'd check the extension education materials for your state or nearby state on needlecasts for available control methods.