Preventive Tree Spraying

Aspen Scale

Aspen Scale, also known as Willow Scale and Poplar Scale is an armored scale which is adversely affecting Aspens, Willows and Cottonwoods in our mountain communities. Aspen Scale attach themselves in clusters on the trunk, twigs and limbs of the trees in Grand County, Eagle County and Summit County. These insects suck sap and feed through the bark of the tree. This process of sap sucking causes the tree to lose vigor causing branch dieback and girdling of the tree and if left untreated, the possible death of the tree. The scale insect appears in large clusters giving the affected areas a gray mottled appearance.

In Colorado the scale insect overwinters in the egg stage. These eggs are protected by the shell of the dead mother scale which is attached to the bark as well as a waxy shell. The overwintered eggs will hatch in late May through the second week of June. The hatching will vary depending plant location, weather and elevation. Higher elevations will see hatchings in mid to late June. Current thought is that there is only one hatching per year but recent evidence has shown that there is two hatchings a year. The second hatching is evident in late July into August.

Aspen Scale Control Requires Ascent Professionals

The newly hatched insects are called crawlers. Not all crawlers hatch at the same time and are active for a few hours to a few days. This is the only time the scale insects are mobile and vulnerable. Once they find a spot and settle, they begin feeding. At this time they will molt their skins and produce a waxy protective covering making them almost impervious to insecticides.

Armored scales are difficult to control and timing is critical. As mentioned earlier, the scales are mobile for a short time and this time, called the crawler stage, is the optimal time for control. There are several options to consider in devising a management plan. The use of horticultural oils in the spring, before bud break is effective in controlling a portion of the pre hatched eggs. During the crawler stage a horticultural oil combined with an insecticide is the most effective control measure. A second application of insecticide and oil may be required for the second hatching if the infestation levels are high enough to warrant it. An application of a dormant oil in the fall will help control the recently laid eggs. There are systemic soil and trunk applications now available that work well within the tree to control the scale insects as well as alleviating the need for foliar sprays.

Whatever the application required Ascent Tree and Turf Services will properly diagnose your tree issues and offer the best possible solution to maintain your trees health.

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