Evergreens: Scale And Fall/Winter Care

By Marilyn Loser

The Colorado Blue  Spruce trees south of the library have a pretty serious infection of Pine Needle Scale according to State Forester Vince Urbina.  Forester Jeff Burns took a look at the trees in early August and made the same diagnosis. The scale looks like a white powder on the inner branches of the trees.
Burns noted that scale attacks spruce and fir in addition to pine. He said cold temperatures and natural predators, such as ladybird beetle larvae, usually control these insects. Urbina said the abundant new growth on these trees is encouraging. 

Scale infestations flair up in hot, dry conditions. Spraying with an appropriate pesticide (make sure the label refers to scale insects) when the creatures are crawling around can also help, said Urbina. The scale produces 2 generations per year – usually the first emergence is in late May or early June and the second in late July.  While some nurseries suggest using oil, Urbina’s experience is that trees drop their needles after oil is applied. I haven’t seen this scale before in Alamosa; if you have infested trees, please let me know.  According to my research, scale rarely kills mature trees, but it has been known to kill saplings.

If you have young spruce trees and deer graze in your yard, you should consider surrounding the trees with wire fencing that doesn’t bind lower branches.  Make sure deer can’t stick their heads through the fence openings. I’ve seen some evergreens that were bound too tightly, causing severe damage to lower branches.

A 3-4 inch layer of bark mulch out to the drip line helps protect tree roots during dry winters and frequent wide daily temperature swings.  Make sure the bark doesn’t touch the trunk since insects and rot can thrive in the area.

While evergreens don’t shed their needles in the winter, they do enter dormancy—their internal processes slow way down.  However, desiccation (freeze drying) can damage evergreens.  Young evergreens are especially susceptible to drying out from low humidity and high winds during the winter. To help prevent desiccation, keep the ground damp until frost sets in.

Fall is also a good time to plant evergreens. The trees experience less stress during the digging and shipping process because they’re going dormant.  They don't need as much water and sunlight during dormancy as during the spring and summer growth months. Fall planting also gives the trees plenty of time to become acclimated to their new environment and for the soil to settle around the roots.

When deciding where to plant an evergreen in your yard, consider its location in relationship to your home. It’s not a good idea to plant a large evergreen species, such as a Blue Spruce, just south of your house since the tree will prevent the winter sun from warming your home. On the other hand, you might consider planting one on the southwest, a comfortable distance from your house, to block prevailing winds.

When cared for, including proper planting and adequate water, evergreen trees that do well in Alamosa are Ponderosa Pine, Colorado Blue Spruce, Bristle Cone Pine (very slow growing), and Austrian Pine. Some foresters report success planting Ponderosa and Austrian Pines in protected locations. Alamosa has many fine examples of both of these trees: two beautiful Ponderosas grace the north side of Main Street in front of Safeway, and Austrian pines are happy on the west side of Safeway on La Veta Street. See more evergreen choices at AlamosaTrees.net.

Valley floors are often colder than the surrounding mountains, so mountain trees, such as the Engelmann Spruce, are susceptible to having their new growth freeze during spring on the San Luis Valley floor.

Advice from a tree. Stand tall and proud. Sink your roots into the Earth. Be content with your natural beauty. Go out on a limb. Drink plenty of water. Remember your roots. Enjoy the view!” Ilan Shamir