The landscape of Michigan's Lower Peninsula has been changing over the decades. Some of the changes are intentional... some accidental...and some are simply a mystery.
In the 1960's and 70's, Dutch elm disease left tree-lined streets naked.
These last few years saw the Emerald Ash borer leave its trail of destruction across the state. And now Michigan's spruce and pine trees are in decline.
Bert Cregg is an associate professor of horticulture and forestry at Michigan State University.
He says one culprit is called Phomopsis. It's a fungus that has been around for a long time. It used to affect just seedlings and smaller trees. But now it's killing larger trees, too. And scientists don't know why.
"Is this an environmental set of conditions? Is there something going on with the pathogen itself? So there's really lots more questions than answers at this point, other than we're seeing a lot of trees starting to decline."
Cregg says the Phomopsis fungus is primarily affecting blue, white and Norway spruce used for landscaping. Those trees are not native to Michigan.
He says it progressively kills branches... and eventually the whole tree.
Cregg says a couple of things can be done. He says if you spot dead branches, you should prune them ... and get rid of lower limbs to help with air circulation.
He also says if you're planting spruce trees... don't group them closely together, because that makes them more vulnerable to fungus.
And if you're not sure what's going on with your tree: call an expert.
"So if you can get a sample into our diagnostics lab, or another tree care provider that knows what they're looking at. If it can be identified as Phomopsis, then there is a possibility of treating with a fungicide."
You might also be noticing branch dieback on pine trees along roadways and in state forests. Cregg says any number of things could be causing that... including a type of blight or insects... or maybe just normal variations in weather affecting tree growth. They just don't know yet.