You may have noticed some sadder than usual looking evergreens this past year and wonder what just happened? Well, it didn’t exactly just happen. What you’re seeing is drought stress from spring 2021. Trees work on a slower timeline than the rest of us so while it may appear to you that a perfectly healthy tree took a turn for the worse overnight, it’s most likely a delayed symptom from a much earlier cause.
A browning spruce or pine isn’t very aesthetically pleasing, especially this time of year when it’s their time to shine. Not only that, this decline is actually a siren call for a lot of damaging pests like Ips beetle, or “engraver beetles.” These are tiny bark beetles that can ultimately kill a tree by tunneling just underneath the bark, girdling the tree with its galleries. They rarely go after healthy trees, but prefer drought stressed targets. While only ⅛-⅜” long, these tiny beetles can be quite damaging pretty quickly, with 2-4 generations a year beginning to emerge in the spring and continuing into late summer. The most common species spotted in the Denver area lately have been Ips ipini and Ips hunteri, ponderosa pine ips beetle and spruce ips beetle. Symptoms of an infestation can look like many things, but most commonly is dieback from the top down, a rust orange fading of the tree needles and presence of boring saw dust in the crevices of the bark. So, while drought stress is a slow death, ips beetles operate much quicker in taking down your beloved tree.
The first line of defense here in our urban forest is to maintain proper watering techniques for your evergreens. Remember, our trees continue to need water throughout the winter. Using a hose on a trickle, or a sprinkler, try to water the base of your tree for at least 30 minutes between the months of October and April. Pick a day that is over 40 degrees and aim for the first part of the day to prevent any overnight freezing.
Preventative insecticide treatments are also an option in the early spring. This is something to consider if you notice fading and declining spruce or pines in your neighborhood. Once the male ips beetle makes a home under the bark, he signals to females to come join him to reproduce, so one infested tree invites more unwanted visitors to the neighborhood.
