Colorado blue spruce, our state tree, is one of the most popular ornamental trees in Fort Collins and other communities along the Front Range. This beautiful tree, which grows naturally along creek bottoms throughout the Colorado Rockies, is long lived, fairly fast growing and has attractive foliage in hues of blue, blue green and blue-gray.

Unfortunately, during the past several years, many of these tall, elegant trees have died. They have fallen victim to a combination of drought and a damaging bark beetle.

Five successive years of below normal precipitation have put our forests and urban trees under moisture stress. It's a well-known fact that when pines, spruces and other conifers are stressed by rainfall deficit, they become susceptible to bark beetle attack. In the case of blue spruce, the culprit is a native bark beetle known as the blue spruce engraver beetle known to entomologists as Ips hunteri.

Bark beetles are tiny insects. The adult beetles range in size from a grain of rice to about one-quarter inch long, are cylindrical in shape and usually brown to black in color. They breed under the bark of the trees. Attacking beetles bore through the bark into the cambium, a single layer of cells between the bark and the wood, and construct a network of galleries in which they lay eggs. In order for these attacks to be successful, thousands of beetles must attack the tree almost simultaneously. The attacking beetles are attracted to stressed trees because of odors the trees produce and attractant chemicals produced by the attacking beetles. The eggs hatch into legless, white, c-shaped larvae. The larvae feed in galleries that they construct in a more or less perpendicular direction to the egg galleries. When the larvae have finished feeding, they pupate in cells at the end of the larval galleries. The pupa then become adults that emerge from the inner bark, fly to other susceptible trees, attack and repeat the process. Trees attacked by bark beetles are killed by the girdling action of the adults and larvae. Wood staining fungi, which the attacking beetles introduce into the tree, hasten tree death.

The blue spruce engraver beetle is a member of a group of bark beetles known as engraver beetles. About 60 species are known throughout the conifer forests of the northern hemisphere and 25 species are found in forests across North America. The North American engraver beetles attack either pines or spruces. Several species of engraver beetles are native to Colorado. A related species, the piñon engraver beetle (Ips confusus), is presently killing large numbers of drought stressed piñon pines in southern Colorado and other southwestern states. The blue spruce engraver is found throughout the natural range of Colorado blue spruce. In recent years, this beetle has expanded its range to include the urban forests along the Front Range where its host tree, Colorado blue spruce has been widely planted.

In the case of engraver beetles, the male beetles initiate the attack process. They bore through the bark and construct a nuptial chamber in the cambium layer. The males are then joined by between two and five females. After the male mates with each female, she constructs an egg gallery and lays eggs, individually, along each side of the gallery. The end result is an elaborate network of galleries radiating from the nuptial chambers in an "I, Y or H" shaped pattern.

The most conspicuous evidence of bark beetle attack is when the foliage of infested trees suddenly turns a reddish brown color. In the case of spruce engraver beetle, attacks typically begin in the upper crown and only the upper third or half of the crown changes color. Usually, the emerging brood beetles will re-attack the same tree lower in the crown and eventually kill the entire tree. Other evidence of bark beetle attack includes the presence of reddish-brown boring dust and small reddish pitch tubes on the bark surface. Peel back the bark and you will see the galleries as well as the bark beetle life stages. If the brood adults have completed their life cycle and emerged, the bark will contain hundreds of tiny, round exit holes.

The blue spruce engraver is a difficult insect to control. Because it makes its first attacks in the upper crown, infestations are almost impossible to detect in the early stages. By the time conspicuous symptoms appear, the tree is dying. All that can be done is to remove the tree and destroy the infested portions by chipping or burning the bark. Infestations can be prevented through regular watering of ornamental blue spruce during dry periods. Preventative sprays, such as those used against the mountain pine beetle, can be effective, provided that the spray is applied to the upper bole of the tree where the first attacks typically occur.

If you have trees that you believe may be attacked by bark beetles, you can call the Larimer Country Office of the CSU Cooperative Extension Service at (970) 498-6000 for verification and advice on how to treat infested trees.

Q: Are pansies easy to grow?

A: On chilly nights and in chilly weather, the pansy keeps right on blooming when temperatures dip to the 20's. They are the perfect plant to liven up the garden during times when little else is in flower. Pansies have few disease and insect problems and are quite versatile. Their vibrant rainbow of available colors can be massed in beds, potted as an accent, worked in as a border and they can stand-alone. Pansy petals are edible and add color to salads. There are around 150 varieties and many are perennials. Most pansies are treated as annuals and they do need a few hours of sun each day in order to flower well. Pansies will not tolerate the heat of full summer sun.

Q: I am aching to caress the good earth and smell things growing. My garden is soggy and many of my plants are emerging tender shoots. Is it too early to work the soil?

A: The urge to get out and dig, rake and cultivate is fearsome for us gardeners, but walking on the soggy spring soil compacts the earth and destroys the structure of the soil. To be sure the soil is workable, grab a handful of soil and squeeze. If water runs out or the soil stays compacted in one sticky lump, it is too wet to work.

Q: Can I put my new tomato plants in the garden the day I buy them?

A: It is best to "harden off" most tomato plants before planting them outside. This will allow the plants time to adjust to the colder temperatures. Start by leaving them outside for a few hours each day lengthening the time outdoors gradually until planting day.

Q: How do I know which lawn care product is best for my yard and why is there such a variation in price?

A: Lawn care products can vary in the amount and type of fertilizer they contain. In addition, some have coatings so the active ingredients are released over time or with moisture. Often bags have the same exact ingredients but you pay less for simpler packaging. Educating yourself about the type of grass you have and identifying the weeds that are a problem will help you make educated choices. You can also get information from Fact Sheets #3.100 - Broadleaf Weed Control in Lawns, #3.101 - Grassy Weed Control in Lawns, and #7.202 - Lawn Care.

In addition to sharpening the edges of your gardening tools, it is a good idea to sharpen the blades on your rotary lawn mower. An initial sharpening, followed by maintenance sharpening once a month, will provide a cleaner cut with less scalping of your turf. Scalping promotes shallow root development which reduces the overall drought tolerance of the turf; a deep root system can more effectively tap into available water.

When buying seeds, it is important to check the lot identification number. This is often stamped along the margin of the seed packet. The label should read "packed for 2004 lot 1", for example.

Arbor Day is just past but it's not too late to help save our shade! If you're looking to plant a tree, why not try a Colorado native. The benefit of gardening with native plants is that they are naturally adapted to Colorado climates, soil types, and environmental conditions when planted into a similar type landscape. Two deciduous natives to try are the Gambel oak (Quercus gambelii) (the acorns provide an excellent source of wildlife food) or the smaller American plum (Prunus americana) (another wild life attractant).

The authors have received training through Colorado State University Cooperative Extension's Master Gardener program and is a Master Gardener volunteer for Larimer County.

Gardening and Insect Fact Sheets are available on-line by clicking HERE.

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This page updated:  May 4, 2004