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Mountain pine beetle is considered the most destructive insect pest of Colorado’s forests. This small, dark brown to black beetle, native to the western United States and Canada is a member of a large family of beetles known as bark beetles. Bark beetles attack trees in large numbers and construct breeding galleries in the tree’s cambium layer, the region between the bark and wood. Gallery construction girdles and kills trees. Wood staining fungi, introduced by the attacking beetles hasten the tree’s death. Trees are typically attacked in groups of anywhere from 5 to several hundred trees. In Colorado, mountain pine beetle attacks ponderosa, lodgepole and sometimes limber pines. Other Colorado bark beetle species attack and kill spruce and Douglas-fir. The smaller European elm bark beetle, the insect that spreads Dutch elm disease in our urban areas, is also a member of the bark beetle family
Mountain pine beetle infestations are easily recognized by the presence of groups of dead and dying pines in the forest. The bark crevasses of attacked trees have pitch tubes and a reddish brown boring dust. Pitch tubes are small pockets of crystalized resin caused by the attacking beetles and resemble popcorn. Peel back the bark and you will see the characteristic galleries and white grub-like larvae
Mountain pine beetle outbreaks are a fairly common occurrence in western pine forests. During the late 1970s and early 1980s, there was a major outbreak of mountain pine beetle along the entire Front Range. The key factor that favors outbreaks is the health of the forest. Ponderosa pine grows naturally in open, park-like forests. Before European settlement, frequent natural fires helped to maintain this condition. Fires have been largely eliminated from these forests and today they often have trees than the site is able to support. These forests are under stress and vulnerable to beetle attack. Other factors that make ponderosa pines more susceptible to beetle attack are root disease fungi and dwarf mistletoe, a parasitic plant that attacks and weakens trees.
Woodland owners can help prevent mountain pine beetle attacks by keeping their ponderosa pine forests in a healthy, vigorous condition. Dense patches of pines should be thinned to create a natural, more open stand. During thinning, trees with sparse, open or partially dead crowns and trees infested with dwarf mistletoe should be removed. If other trees, such as aspen, spruce or Douglas-fir are present, thinning should be designed to create a mixed species forest.
Once a tree is attacked, there is nothing that can be done to keep it from dying. Trees with mountain pine beetle broods should be cut and steps taken to destroy the brood. This can be done by cutting trees and peeling or burning the bark, or exposing infested logs to high solar radiation (more then 110 degrees F) by covering them with sheets of clear plastic. Beetle attacks in individual, high value trees can be prevented by an application of carbaryl (Sevin) or permethrin (Astro) insecticide to the bark in spring or early summer prior to beetle flight. Follow label directions when applying insecticides. One application should protect ponderosa pines for a growing season.
Q: How can I encourage my irises to produce lots of flowers?
A: Irises should be thinned to avoid overcrowding. Overcrowding results in reduced flowering will also cause some of the more aggressive, older cultivars to crowd out less aggressive cultivars, causing them to eventually disappear from an iris bed.
Q: When should I thin my iris bed?
A: Iris beds should be thinned after flowering has ended. In this area, July and August is a good time for thinning irises because new plants have begun to form on the rhizomes.
Q: How often should I thin my iris bed?
A: Once every three years is a good interval. Label each clump of irises in your bed by color or cultivar name when they are in flower. Dig up each rhizome and separate it into clusters of 3 to 4 shoots. Discard the old portion of the rhizome containing the plants that have bloomed and replant some of the newly separated clumps. Surplus rhizomes can be given to friends and neighbors, especially fellow iris lovers. This is a great time to swap rhizomes and introduce new cultivars into your collection.
Q: Are there any vegetables that come back year after year?
A: The three most common perennial vegetables in Colorado are asparagus, horseradish and rhubarb. Asparagus and rhubarb are early garden vegetables while horseradish is harvested in autumn. Since horseradish is most often prepared as a condiment two or three plants should suffice for the average garden. These vegetables are hardy, relatively pest-free and easy to maintain once established. All are suited to gardens up to 10,000 feet in elevation. They will produce for many years in the same location.
For more information on growing perennial vegetables in your garden, see Fact Sheet 7.615 - Perennial vegetables.
Lawns with compacted soil provide perfect areas for weed growth such as broad-leaved plantain, knot weed, prostrate spurge and goose grass. One of the best ways to reduce soil compaction is by aeration.
Get an early start on weeds in the vegetable garden. Pull weeds in the rows and also 1-inch to 2-inches around each plant to eliminate competition for water and nutrients.
Plant dill, parsley, and fennel to attract larva of the beautiful Black Swallowtail Butterfly. The caterpillars or larval stage are light green with black stripes and yellow or orange spots.
Buy bedding plants without blooms or pinch off the flowers and any buds when transplanting. This will encourage better initial root growth after transplanting and will give you a bushier plant with more blooms.
If you staked newly planted trees, remember to remove them after the first growing season. This is also the time to remove any tree wrap that you might have used last winter to prevent sun scald. Tree wrap left on during the summer months will harbor insects and promote disease growth.
The author has received training through Colorado State University Cooperative Extension's Master Gardener program and is a Master Gardener volunteer for Larimer County.
Fact Sheets are available at the Larimer County Extension Office, 1525 Blue Spruce Drive, Fort Collins, Colorado, telephone (970) 498-6000, or contact us by e-mail at larimer@coop.ext.colostate.edu
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