-Keeping Your Aspen Healthy

  • Maintain a proper watering schedule – aspen will suffer if over- or under-watered.

  • Prevent direct sprinkling of leaves by lawn watering systems.

  • Unwanted aspen sprouts that appear in the lawn may be mowed. DO NOT spray the sprouts, as they are connected to the mother tree.

  • Avoid wounding the main trunk with movers or weed wackers.

  • Trim out cankers that are less than half the circumference of the aspen.

  • Clean up heavy scale-insect infestations.


Adult Emerald ash borer

Adult Emerald ash borer

 -Emerald ash borer (Agrilus planipennis; EAB) is an insect native to Asia and introduced into North America sometime during the 1990’s. Since its initial discovery in Michigan in 2002, this insect has killed millions of ash (Fraxinus spp.) trees throughout the central and northeastern United States and Canada. It is now considered the most destructive tree insect pest ever to be introduced into North America. An Infestation was detected in the city of Boulder in September 2013.


MOuntain pine beetle

MOuntain pine beetle

-Mountain pine beetles (Dendroctonus ponderosae; MPB) are native Colorado bark beetles that predominately infest ponderosa pine (Pinus ponderosa), lodgepole pine (P. contorta), and limber pine (P. flexilis). However, numerous species of pines, and all pines found in Colorado are susceptible when beetle populations explode, including ornamental pines.


Adult spruce beetle

Adult spruce beetle

-Spruce beetles (Dendroctonus rufipennis) are native bark beetles that infest Engelmann spruce (Picea engelmannii) and occasionally Colorado blue spruce (P. pungens) in high elevation forests in Colorado. The spruce beetle typically completes a generation in one to three years, with a two-year life cycle being the most common in spruce trees growing above 9,000 feet. Adults fly to seek new hosts in late May through July, preferring large diameter trees until they are depleted from the forest.


IPS beetle

IPS beetle

-IPS beetles, sometimes known as “engraver beetles,” are bark beetles that develop under the bark and tunnel through the tree, damaging and killing pine and spruce trees. Two factors that contribute to ips beetle problems in Colorado include prolonged drought stress and the creation of freshly cut wood (preferred breeding site). Ips beetles are 1/8 to 3/8-inch long and are reddish brown to black. They are similar in appearance to the mountain pine beetle, and it is important to correctly identify the species in order to prescribe an effective management strategy.


Yellow douglas fir beetle

Yellow douglas fir beetle

-Douglas-fir beetle (Dendroctonus pseudotsugae), another close relative of the spruce beetle and mountain pine beetle, is an important native bark beetle of mature Douglas-fir (Pseudotsuga menziesii) forests across most of the West. Outbreaks tend to be associated with mature Douglas-fir forests (average stand diameters greater than 14 inches at 4.5 feet from the forest floor) coupled with periods of below-normal precipitation. Adults typically seek new trees to attack from late spring through early fall. Unlike other bark beetles in Colorado, Douglas fir beetles can use trees that have fallen or been cut and left for removal at a later date.


Dwarf Mistletoe

Dwarf Mistletoe

-Dwarf mistletoes are parasites of native conifer forests that can cause severe damage. Dwarf Mistletoe: Parasitic Plants

Forty-two species of dwarf mistletoe are known worldwide; five species are found in Colorado’s forests. Most dwarf mistletoes are native to western North America, from Alaska south through the western United States, Mexico and Central America.

Dwarf mistletoe, a common problem in Colorado forests, predominantly affects ponderosa and lodgepole pines, although they can attack Douglas-fir, piñon, limber and bristlecone pines.