Colorado is home to many different insect which require unique and safe methods to maintain them. At TropicGreen we pay special attention to detail and craft a program which will effectively maintain any problem insects while saving you money.

 

Ips Beetles

by W. Cranshaw and D.A. Leatherman¹

Quick Facts...

• Ips is a common group of bark beetles that infests pine and spruce trees.
• Ips beetles rarely attack healthy trees. Most problems with ips occur to newly transplanted pines or when plants are under stress.
• Several generations of ips can occur in a season.
• There are 11 species of ips beetles found in Colorado.

Ips beetles, sometimes known as “engraver beetles,” are bark beetles that damage pine and spruce trees. They develop under the bark and produce girdling tunnels that can cause dieback and kill trees. Eleven species of ips beetles occur in Colorado (see Table 1 below).

Table 1. Common ips beetles (Ips species) affecting pines and spruce in Colorado.
Species	Hosts	Comments
Ips hunteri	Spruce	This is a common species affecting Colorado blue spruce in landscape settings. Upper portions of the tree are typically infested first.
Ips pilifrons	Spruce	A forest species often called the “spruce ips”; tends to infest the upper part of fallen trunks.
Ips pini	Ponderosa, lodgepole	The most common species associated with other pines pines in Colorado.
Ips knausi	Ponderosa pine	Common at base of trunk and in fresh stumps.
Ips calligraphus	Ponderosa pine	Largest ips species in Colorado; often in main trunk.
Ips confusus	Piñon, rarely other pines	Periodically kills piñons over large areas.
Ips latidens	3- and 5-needled pines
Ips borealis	Engelmann spruce
Ips integer	primarily Ponderosa pine
Ips woodi	Limber pine
Ips mexicanus	Lodgepole and limber pines

 

Ips beetles are generally not considered as destructive or aggressive as bark beetles in the genus Dendroctonus (mountain pine beetle, spruce beetle, Douglas-fir beetle). Normally ips beetles limit their attacks to trees that are in decline due to root injuries, wounding, or other stresses. However, under widespread conditions which allow improved survival and large population build-ups, ips beetles are a considerable threat to living trees. Two factors that recently contributed to ips beetle problems in Colorado include: prolonged drought stress; and the creation of freshly-cut wood (which is a prefered breeding site) from forest homeowner efforts to reduce wildfire hazards.

Figure 1: Adult Dendroctonus (left) versus Ips (right). Note gradually curved wing of Dendroctonus. Actual size of Dendroctonus from 1/8 to 1/3 inch, Ips 1/8 to 3/8 inch.

Ips beetles are small (1/8 to 3/8 inch long), reddish-brown to black beetles. They have a pronounced cavity at the rear end, which is lined with three to six pairs of tooth-like spines, depending on the species. The latter feature distinguishes them from other bark beetles (see Figure 1).

Symptoms of Ips Beetle Injury

Top dieback of spruce from drought stress and ips attack.

Storing cut firewood near susceptible trees greatly increases the risk of ips beetle attack.

As adult ips beetles enter trees and tunnel, a yellowish- or reddish-brown boring dust is produced and accumulates in bark crevices or around the base of the tree. When the larval tunnel, affected parts of the tree discolor (“fade”) and die.

These symptoms may be limited to parts of the tree, such as a single branch or the top. However unlike mountain pine beetle, infestation by ips beetles does not necessarily mean the whole tree will die, but over time, attacks may progress as later generations “fill” the tree and then ultimately the host can die.

Small round holes in the bark of infested trees indicate the beetles have completed development in that part of the tree and the adults have exited. The presence of these holes peppering the bark show the beetles have moved to another part of the same tree or to neighboring trees.
Woodpeckers are common predators of ips beetles. Their presence may also indicate bark beetle activity. Woodpeckers often remove the tree bark in an effort to obtain this food source. This habit results in ragged holes or patches of missing bark on the tree.

Generalized Life History

Adults overwinter under the bark or in surrounding litter at the tree base. They begin to attack weakened trees in the spring. Initially the male enters the tree, constructs a cavity under the bark known as the “nuptial chamber.” Females are attracted to the tree by chemicals (pheromones) produced by the male.

After mating, females (usually three) excavate egg galleries off the central chamber. The tunnels produced by the adults appear as a “Y”- or “H”- shaped pattern. These galleries are mostly free of boring dust, which is pushed out of the entrance hole as the adult beetles work. These “cleared out” galleries have a different appearance than the debris-filled galleries of Dendroctonus. Eggs are laid along the gallery and young larvae soon hatch and begin tunneling smaller lateral galleries that lightly etch the sapwood. They are small grubs, about 1/4 inch long when mature, white to dirty gray, legless, with dark heads. In Colorado, two to four generations of these beetles usually develop per year.

Boring dust at the base of a pine tree. Reddish boring dust is caused by ips beetles. The whitish dust is from ambrosia bark beetles.

Tunneling by Ips hunteri in blue spruce.

Management

To prevent ips beetle attacks, use practices that promote vigorous tree growth. Properly siting trees in landscape plantings is important to allow optimal growing conditions as the tree matures. Adequate – but not excessive – water may be needed. Root injuries caused by mechanical damage, compaction, or disease should be avoided.

Freshly-cut material that results from pruning or thinning practices (called “slash”) should be removed from the vicinity of valuable trees. Never stack green or infested coniferous wood next to living coniferous trees. Such green woody material should be chipped or treated so that the inner bark area is destroyed. Ips larvae will not survive standard chipping or debarking treatments. Other treatments could include scattering (as opposed to piling) slash to promote rapid drying.

Trees at risk of ips attack include newly transplanted trees, trees suffering root injuries from construction, and trees surrounded by large breeding populations of ips beetles. These types of trees can benefit from preventive insecticide applications.

Insecticides are used as drenching preventive sprays on the trunks and larger branches. These insecticides need to be applied prior to adult beetle infestation. (Remember that overwintering beetles begin emerging in spring as soon as daytime temperatures consistently reach 50 F to 60 F.) However, timing can be difficult to determine since ips beetles can have multiple, overlapping generations and life cycles. Adults have been observed entering trees during warm days as early as late-February on through November. Because of this extended activity, two treatments (early spring and summer) may be needed to protect trees during high-risk conditions.

Insecticides used to prevent ips include either permethrin, bifenthrin, or carbaryl (Sevin) as the active ingredient. There are many products currently on the market containing these active ingredients. Follow the manufacturer’s recommendation for the proper rate for bark beetle treatment. Bark beetle applications at the labeled rate should provide at least three months control of ips beetles.
When a preventively-sprayed tree later dies of beetle attack, it is usually for one of the following reasons: 1) the tree was sprayed after it was attacked; 2) the spray was applied at too dilute a rate; 3) the entire bark surface of the susceptible part of the tree was not sprayed; or 4) the material wore off and was no longer effective.

Note: Concentrations of insecticides used to control bark beetles are often considerably greater than those used for insects on foliage. To avoid needle burning, try to limit the application to the bark, particularly when using liquid (emulsifiable concentrate) formulations that have increased risk of causing plant injuries.

Insecticide applications are not needed when ips beetles do not pose a serious risk to healthy trees. Ips problems are often an issue for a few years, then lessen naturally to non-threatening levels. This is the normal condition in Colorado. A rule of thumb when deciding if preventive treatments are needed is to survey for infested groups of bark beetle-killed trees (as determined by dead foliage) within sight of the live trees in question. Also, transplants or recently disturbed trees in natural forest areas or near other known sources of ips may warrant protection. Tree value, of course, is always a consideration. There is often more interest in protecting high-value trees such as those around residences, golf courses, or in other highly visible settings.

No chemical treatment exists for trees or wood already infested by ips beetles. In rare cases where it is feasible to reduce the threat to live trees by killing beetles within infested trees before they exit, treatments involve bark removal, chipping the wood into small pieces, covering piles with a double-layer of 6-mil thick clear plastic sealed around the edges with soil to heat (solarize) the wood, or physical removal of infested material from the site to an area a mile or more from susceptible trees.

Ips confusus pitch tubes on infested pinyon pine trunk.	Ips pini egg galleries under bark of ponderosa pine trunk..

¹ W. Cranshaw, Colorado State University Extension entomologist and professor, bioagricultural sciences and pest management; and D.A. Leatherman, Colorado State Forest Service entomologist (Retired). This fact sheet was produced in cooperation with the Colorado State Forest Service. 12/02. Revised 11/06.

Colorado State University, U.S. Department of Agriculture, and Colorado counties cooperating. Extension programs are available to all without discrimination. No endorsement of products mentioned is intended nor is criticism implied of products not mentioned.

Aphids

Aphids can be serious pests in Colorado. The small, pear-shaped insects vary in color from green to orange, red, brown or gray. These insects damage plants by sucking the plant juices. When abundant, aphids remove large quantities of sap, reducing the growth and vigor of the plant.

One can look for certain signs on a plant to verify the presence of aphids. Leaf curling, the presence of ants or the excretion of a sweet, honeydew-like substance may all be an indication of an aphid problem.

Ladybugs, green lacewings, syrphid flies and parasitic wasps are some of the aphids' natural enemies and will help control them. Most plants will tolerate the use of insecticidal soaps. Test spray a small portion of the plant. Wait a few days and see if there is sensitivity to the foliage. If no symptoms appear then spray the entire foliage. High water pressure may also wash away aphids and remove sticky honeydew.

When aphids can't be controlled by these natural methods, insecticides like acephate, bifenthrin, and imidacloprid are effective. Be sure to follow all label directions when using insecticides.

 

 

 

Bark beetles

Among evergreen forest insects, bark beetles are a very prominent problem. The most notorious of the bark beetles is the mountain pine beetle. Various forested areas throughout Colorado have sustained extensive damage from mountain pine beetle attacks.

In urban areas, however, the primary culprits are typically one of the various Ips species. Ips can frequently be found in ponderosa, lodgepole, piñon, limber, Austrian and bristlecone pines as well as spruce.

There are no insecticides that will kill beetles after they have successfully infested a tree. Permethrin and carbaryl are effective preventatives against both mountain pine beetle and Ips beetle.

When Ips beetle infested trees are cut down, the resulting piles of slash can still harbor the insect. It takes about six weeks for Ips beetle to go through their life cycle in the piles. Ips will attack freshly cut bark that is intact and fairly moist. After they have emerged from the cut logs or the bark pulls off easily, it is no longer a source for Ips to go through their life cycle.

There are several species of secondary bark beetles that can be found in evergreens. One example is the red turpentine beetle but other genera of bark beetles include Polygraphus, Scierus and Pityokteines. Preventive sprays are typically not necessary for these beetles as tree mortality is low.

 

 

 

Mountain Pine Beetle

by D.A. Leatherman, I. Aguayo, and T.M. Mehall¹

Quick Facts...

• Mountain pine beetles (MPB) are the most important insect pest of Colorado's pine forests. MPB often kill large numbers of trees annually during outbreaks.
• Trees that are not growing vigorously due to old age, crowding, poor growing conditions, drought, fire or mechanical damage, root disease and other causes are most likely to be attacked.
• For a long-term remedy, thin susceptible stands. Leave well-spaced, healthy trees.
• For short-term controls, spray, cover, burn or peel attacked trees to kill the beetles. Preventive sprays can protect green, unattacked trees.

Figure 1: Adult Dendroctonus (left) versus Ips (right). Note gradually curved wing of Dendroctonus. Actual size of Dendroctonus from 1/8 to 1/3 inch, Ips 1/3 to 1/4 inch.

Mountain pine beetle (MPB), Dendroctonus ponderosae, is native to the forests of western North America. Periodic outbreaks of the insect, previously called the Black Hills beetle or Rocky Mountain pine beetle, can result in losses of millions of trees. Outbreaks develop irrespective of property lines, being equally evident in wilderness areas, mountain subdivisions and back yards. Even windbreak or landscape pines many miles from the mountains can succumb to beetles imported in infested firewood.

Mountain pine beetles develop in pines, particularly ponderosa, lodgepole, Scotch and limber pine. Bristlecone and pinyon pine are less commonly attacked. During early stages of an outbreak, attacks are limited largely to trees under stress from injury, poor site conditions, fire damage, overcrowding, root disease or old age. However, as beetle populations increase, MPB attacks may involve most large trees in the outbreak area.

A related insect, the Douglas-fir beetle (D. pseudotsugae), occasionally damages Douglas-fir. Most often, outbreaks are associated with previous injury by fire or western spruce budworm. (See fact sheet 5.543, Western Spruce Budworms). Spruce beetle (D. rufipennis) is a pest of Engelmann and Colorado blue spruce in Colorado. Injured pines also can be attacked by the red turpentine beetle (D. valens).

Mountain pine beetles and related bark beetles in the genus Dendroctonus can be distinguished from other large bark beetles in pines by the shape of the hind wing cover (Figure 1, top). In side view, it is gradually curved. The wing cover of Ips or engraver beetles, another common group of bark beetles attacking conifers, is sharply spined (Figure 1, bottom).

Signs and Symptoms of MPB Attack

• Popcorn-shaped masses of resin, called "pitch tubes," on the trunk where beetle tunneling begins. Pitch tubes may be brown, pink or white (Figures 2 and 6).
• Boring dust in bark crevices and on the ground immediately adjacent to the tree base.
• Evidence of woodpecker feeding on trunk. Patches of bark are removed and bark flakes lie on the ground or snow below tree.
• Foliage turning yellowish to reddish throughout the entire tree crown. This usually occurs eight to 10 months after a successful MPB attack.
• Presence of live MPB (eggs, larvae, pupae and/or adults) as well as galleries under bark. This is the most certain indicator of infestation. A hatchet for removal of bark is needed to check trees correctly (Figures 3, 5 and 8).
• Bluestained sapwood (Figure 9). Check at more than one point around the tree's circumference.

		Figure 3: Top view of adult MPB (actual size, 1/8 to 1/3 inch).
Figure 2: "Pitch tubes" indicating trunk attacks by MPB. Success of the attacks is confirmed by looking under the bark with a hatchet for beetles, their tunnels and/or bluestaining.
Figure 4: Mountain area infested by MPB, showing three years of mortality. Old, dead trees are gray; newly killed trees are straw yellow or orange. Some trees may also be infested but do not turn color until nine months or so under attack.		Figure 5: Larva of MPB (actual size, 1/8 to 1/4 inch). These are found under the bark in tunnels.

Life History and Habits

Mountain pine beetle has a one-year life cycle in Colorado. In late summer, adults leave the dead, yellow- to red-needled trees in which they developed. In general, females seek out large diameter, living, green trees that they attack by tunneling under the bark. However, under epidemic or outbreak conditions, small diameter trees may also be infested. Coordinated mass attacks by many beetles are common. If successful, each beetle pair mates, forms a vertical tunnel (egg gallery) under the bark and produces about 75 eggs. Following egg hatch, larvae (grubs) tunnel away from the egg gallery, producing a characteristic feeding pattern.

Figure 6: Not all pitch tubes indicate successful attacks. Note the beetle trapped in this large pitch tube. If the majority of tubes look like this, the tree may have survived the current year's attack.		Figure 7: Checking beneath the bark for MPB. This attack was successful (note tunnels and stain).
Figure 8: Characteristic tunnels (galleries) of mountain pine beetle made by the adults and larvae. The underbark area looks like this in late spring. Bluestained wood is caused by fungi the beetles introduce.		Figure 9: Cut tree killed by MPB, showing the characteristic bluestaining pattern.

MPB larvae spend the winter under the bark. Larvae are able to survive the winter by metabolizing an alcohol called glycerol that acts as an antifreeze. They continue to feed in the spring and trans­form into pupae in June and July. Emer­gence of new adults can begin in mid-June and continue through Septem­ber. However, the great major­ity of beetles exit trees during late July (lodge­pole pine) and mid-August (ponderosa pine).

A key part of this cycle is the ability of MPB (and other bark beetles) to transmit bluestain fungi. Spores of these fungi contaminate the bodies of adult beetles and are introduced into the tree during attack. Fungi grow within the tree and assist the beetle in killing the tree. The fungi give a blue-gray appearance to the sapwood.

Infested Trees

• Once MPB infests a tree, nothing practical can be done to save that tree.
• Under epidemic or outbreak conditions, enough beetles can emerge from an infested tree to kill at least two, and possibly more, trees the following year.
• Ips and related beetles that emerge early in summer often are mistaken for mountain pine beetle, leading to early reports that "MPB is flying." Be sure to properly identify the beetles you find associated with your trees.
• Trees from which MPB have already emerged (look for numerous round, pitch-free exit holes in bark) do not need to be treated.
• The direction and spread rate of a beetle infestation is impossible to predict. However, attacked trees usually are adjacent to or near previously killed trees.

Tree borers

Borers, insects that develop underneath the bark of woody plants, attack many shade and ornamental trees. Most borers attack trees weakened by drought, mechanical injury, recent transplants, poor soils or root systems. The most important prevention of borers is keeping trees healthy through proper management.

Proper management includes watering trees long enough for moisture to reach the root system of the plant, wrapping young trees from November to April to prevent sun scald, and pruning dead or dying branches to discourage insects.

Some common tree borers include lilac and ash borers, peach tree borer, mountain pine beetle and ips beetle, pinyon pitch mass borers and Zimmerman pine moth. The most common way to control borers, in addition to proper tree maintenance, is chemical control. But borers live inside trees, and treating them with insecticides is difficult. The best time to control borers is when adult are laying eggs on or under bark. Pheromone traps, available for some borer species, help determine if adults are present. Trunk sprays can be effective when borers are in the early larvae stage before they enter the tree.

The most common borer insecticides are Permethrin and Sevin.