One would think that with Dutch elm disease, the smaller European elm bark beetle and several other introduced pests, our elm trees have suffered enough. But now we have yet another new beetle attacking elms in Fort Collins and other Colorado cities.

The new beetle, which entomologists are calling the "banded elm bark beetle," goes by the scientific name, Scolytus schevyrewi. It's a close relative of the smaller European elm bark beetle, Scolytus multistriatus, which is the insect that spreads the tree killing Dutch elm disease. The banded elm bark beetle is native to the Far East and Central Asia including China, Mongolia, Korea, Turkmenistan, Uzbekistan, Tajikistan, Kazakhstan, southern Kyrgyzstan and Asian Russia where it attacks a wide range of broadleaf trees including: elms, weeping willow, Russian olive, pea shrub, apple, cherry and plum. One of its favorite hosts is the Siberian elm, a tree that has been widely planted in the Great Plains as a shelterbelt and windbreak species.

While most bark beetles tend to be a uniform brown color, this new arrival is unusual because it has two distinctive dark brown to black bands on its elytra or wing covers, which makes it fairly easy to recognize. This unusual characteristic has inspired one local entomologist to refer to this beetle the "two-toned schevy."

The banded elm bark beetle was first discovered in the United States during the spring of 2003. The discovery was made as part of a special survey for exotic bark beetles conducted by USDA Animal Plant Health Inspection Service (APHIS) and the Forest Service when beetles were collected in traps near a wood recycling plant in Denver and also in several locations in Utah. Later that summer, infestations were found in New Mexico and Kansas and by the end of 2003, the insect had been found in about 10 western and Mid-western states. Its widespread distribution suggests it has been present for several years. This was confirmed when specimens of banded elm bark beetle were found in an insect collection labeled "Clovis, New Mexico, 1998." How it came to the U.S. is not specifically known but most experts believe it arrived via wooden crates containing small strips of bark carrying imported goods from China and other countries in the Far East.

Banded elm bark beetles bore through the bark of host trees and the females construct a vertical egg gallery where the bark joins the wood. The females deposit eggs individually along the gallery. When the eggs hatch, the larvae feed in galleries roughly perpendicular to the egg galleries. The gallery construction, coupled with wood staining fungi introduced by the attacking beetles kills the tree. This insect is believed to have about three generations a year in Colorado.

Like its cousin, the smaller European elm bark beetle, when the new crop of adult beetles emerges from infested trees, they feed in the branch crotches of elm trees. However, it's not known if this insect can carry and spread the spores of Dutch elm disease during this feeding process. This new beetle has established itself as a tree killer in our area, however. In addition to attacking Siberian elms, it has also attacked and killed American and rock elms in Fort Collins. It prefers to attack trees that are weakened by drought.

The most conspicuous symptom of attack by this beetle is the sudden loss of foliage of elm trees. Closer inspection will show a white boring dust on the bark surface of infested trees. Removing the bark will reveal egg and larval galleries and the presence of white colored larvae and pupae. Unfortunately, by the time these symptoms appear, the tree is already dead and the only treatment is to remove the tree as quickly as possible and destroy the bark and wood by chipping.

People residing in Larimer County who suspect that their elms are infested by the banded elm bark beetle, smaller European elm bark beetle or other pests, can contact either the Larimer County Cooperative Extension Service, or the Colorado State Forest Service, to help identify the problem and the most suitable treatment.

Q: This year the leaves on my hollyhocks look awful. What can I do?

A: If the leaves are covered with powdery orange spots, your hollyhocks probably have rust, a type of fungus that often afflicts hollyhocks. If you discover the problem early in the season, you can try to remedy the situation. Remove effected leaves, apply a fungicide and avoid overhead watering. Next year, try planting your hollyhocks in a different spot, away from soil that may contain the rust spores, and always water your hollyhocks at the base of the plant. Also, you might want to try planting the rust-resistant variety of hollyhock, the pale yellow Alcea rugosa.

Q: Can you recommend a vine that will cover a chain link fence fast?

A: If the fence is in a shady area, you might try Dutchman's pipe. It is a vine with large, heart-shaped leaves that will lay completely flat against a fence, and it has an inconspicuous pipe-shaped flower. If the fence is in sun, you could try silver lace vine, grapes, Virginia creeper, or sweet autumn clematis. Silver lace vine is a drought-tolerant vine that features lovely sprays of small white flowers in summer. Virginia creeper also tolerates drought. It has large green leaves that turn a vibrant scarlet in the fall. Sweet autumn clematis is a fall-blooming clematis. Its hundreds of white flowers smell like almonds.

Q: My bee balm is covered with white flecks. What are they, and how do I get rid of them?

A: Your bee balm (Monarda didyma) probably has powdery mildew. Powdery mildew is a fungus that produces spots that look like talcum powder on the newer foliage of plants. A variety of plants get powdery mildew (roses, asters, bee balm, and cucumbers) but many different species of the fungus are responsible for the disease on different plants. Generally, powdery mildew affects plants that are in a bit of shade during the day and in areas of poor air circulation. Fortunately, powdery mildew is usually most in evidence after bee balm has bloomed. Once powdery mildew has developed on bee balm, it is best to cut the diseased foliage back to the leaves at the base of the plant. Dispose of the leaves, and do not compost them. Next spring, you might want to consider moving your plant to an airier, sunnier location and thinning out some stalks of the plant. You might also investigate varieties of bee balm that are more mildew resistant like Jacob Cline (red), Marshall's Delight (pink), or Violet Queen.

Q: This year my perennial geranium had a nice mounded form at the beginning of the summer but now is messy looking and falling open. Is it okay if I cut it back?

A: Many of the larger perennial geraniums (geraniums that do not need to be replanted every year) tend to flop around once they have flowered. It is safe to cut these plants back. If possible leave some of the leaves, but for some geraniums, like Johnson's Blue, it is all right to cut the plant right down to the ground. It will rebound and start producing new shoots very quickly.

The Larimer County Farmers' Market starts today from 8 a.m. to 12 noon at Remington and Oak in Old Town Fort Collins. Come down and shop for fresh local produce, plants, cheese, bakery items and more.

Do something kind for your plants and yourself. A good layer of organic mulch helps conserve moisture, prevents weeds and improves the appearance of your landscape and flower beds. Keep mulch away from plant stems and tree trunks to allow adequate air circulation at the base of the plants.

Avoid over-watering by using a rain gauge or published rainfall data to determine how much additional water to apply to your lawn and garden. Water use reports are available on the Northern Colorado Water Conservancy District web site at www.ncwcd.org/ims/ims_Weather_form.asp.

Encourage healthier, water-conserving turf by setting your mowing height at 2-1/2 to 3 inches. For best results, mow frequently enough to remove only one-third of the turf's total height at any one mowing, especially if you are using a mulching mower. Sharpen your mower blade every 4 to 6 mowings.

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:  June 29, 2004