The loss of the interior needles on a coniferous tree in the fall is a natural process. Conifers retain their needles for several years but as new needles are produced every year there are always some that will be shed in the fall.
What’s The Problem?
This usually takes place gradually however it is alarming when many needles turn colour at the same time and the tree appears to be dying. There are many stress factors that can increase the severity of the needle drop; drought, standing water, herbicide injury, insect and disease infestations, and root injuries.
What Can I Do?
There are no control measures necessary for this other than doing your best to keep your trees healthy.