Oct 15, 2010 2:02 PM by Bea Karnes
We're used to seeing golden aspen leaves in autumn, but yellow or brown needles on pine trees in unnerving. Thoughts of pine beetle deforestation come to mind.
But the Colorado State Forest Service Cañon City District office is telling us not to worry, that most of the evergreen trees along the southern Front Range with are going through a natural shedding process, and are not infested by bark beetles or tree disease.
"It's fall now, which means we're in peak needle-drop season," said District Forester John Grieve. "The yellow, dying needles people are seeing on their pine and fir trees are simply part of a natural cycle."
According to Grieve, every autumn, many Colorado evergreen tree species shed some of their older, interior needles as part of an annual growth cycle. Needles on the lower portion of the crowns or closest to the trunk are most commonly shed, but trees stressed due to drought or root damage may shed more needles to keep the tree in balance with its root system. Soon-to-be shed needles typically turn yellow first, then a reddish-brown color before dropping off; very small branches with few needles on them also may die.
Needle dropping is especially prevalent in ponderosa pine and white fir.