Category Archives: Tree Problems

Emerald Ash Borer- Exotic ash pest

Emerald Ash Borer (EAB)

Since its detection in Detroit in 2002, EAB has wreaked havoc on millions of ash trees across 23 states and 2 provinces. EAB has been very destructive to native ash trees due to host naivety and lack of natural enemies. However, individual trees can be saved with insecticides.

Until recently, EAB has only been known to feed on true ash species (Fraxinus spp.). However, it has now been confirmed that white fringe tree can serve as a host as well.

Identification

Trees infested by EAB tend to show many symptoms. These can include thinning of the canopy, branch dieback, “D” shaped exit holes in the trunk and branches, excessive shoots in the crown and/or base of the tree, excessive wood pecker activity, bark splits and tunneling underneath bark. The adult beetles are smaller than the diameter of a penny, metallic green, and can be seen flying in early summer.

Life Cycle

Adults emerge when black locust are in bloom, which usually occurs at the beginning of June. Adult beetles then feed on ash foliage for approximately two weeks before mating and laying eggs on the bark. Larvae hatch and burrow into the tree where they feed and form galleries just behind the bark. Once ready for pupation, larvae will burrow approximately another ½ inch or so into the wood. They overwinter either as larvae or pupae until spring.

Damage

Damage occurs during the larval stage. EAB feed and create their galleries in the living tissue just beneath the bark. Without this tissue, trees cannot actively move nutrients effectively and trees essentially starve to death. This process typically takes anywhere from 1-3 years, but varies depending on the condition of the tree.

Management

Once EAB gets into an area, it is likely that nearly 100% of ash trees will be killed unless treated with insecticides. That’s not to say that all trees SHOULD be treated. The site location and health of the tree should be taken into consideration before the decision of investment in treatments. Another important factor to consider is the distance you are from the areas where EAB has been detected. In the Midwest, it is recommended that if you are within 10-15 miles of a detection zone that you begin to plan for treatment. Some experts claim that you should not be treating unless you are 5 miles within a detection zone. Either way, a management strategy should be in place if EAB is nearby.

There are four systemic insecticides that are recommended to treat EAB: imidacloprid, dinotefuran, emamectin benzoate, and azadirachtin. Though emamectin benzoate seems to be the most effective treatment against EAB (especially on larger trees), all four insecticides have been shown to be good tools.

For more information on EAB and insecticide options, please follow the links below:

Emerald Ash Borer in Colorado: https://www.colorado.gov/agplants/emerald-ash-borer

Insecticide Options for Protecting Ash Trees from Emerald Ash Borer:  http://extension.entm.purdue.edu/EAB/PDF/NC-IPM.pdf

FAQs Regarding Potential Side Effects of Systemic Insecticides Used to Control EAB:  http://www.emeraldashborer.info/files/Potential_Side_Effects_of_EAB_Insecticides_FAQ.pdf

Issues Stemming from Poor Planting/Aftercare

Issues Stemming from Poor Planting/Aftercare

Unfortunately, often too many times trees are miscared for after they are planted. Ties that are used to attach the newly planted tree to the tree stake to stabilize them are left on and girdle trees. Trees are planted too high or shallow. Burlap sacks and wire cages are left around the root ball while planted. Layers upon layers of mulch are mounded up around tree trunks. These types of practices will always lead to further problems down the road.

Stabilizing small trees after planting to withstand wind or correct growing habits is a common practice. However, the bands or wires used to attach tree trunks to stakes need to be removed once the tree’s roots have taken hold. Otherwise, trees will grow into the band and girdle themselves.

Burlap sacks and root ball cages need to either be completely removed when planting, or pulled away from the top 2/3 of the root ball so that roots can grow laterally, unrestricted. When these are left intact, roots will grow in a circular pattern around the trunk and cause root girdling. Also, sometimes trees are planted too deep in nurseries and the top layer of soil around the base of the trunk needs to be removed to expose the root flare of the tree.

Everyone likes to use mulch around the base of their trees as it increases the aesthetics of the landscape and actually provides benefits to the root zone of trees. However, NEVER pile up mulch around the base of the tree. This increases moisture around the base of the trunk which provides a suitable environment for decaying pathogens. Also, some soil dwelling rodents will chew on the trunk while protected under the mulch. Only place, at most, a couple inches of mulch thickness around the tree leaving a couple inches around the base of the trunk. Remove old mulch before adding newer mulch to avoid mulch accumulating around the tree.

Mountain Pine Beetle- Browning Needles

Mountain Pine Beetle- Browning Needles

A bark beetle that destroys the cambium and introduces the blue stain fungus in Ponderosa, Lodgepole, Scotch and Limber pine trees. It is fatal to most trees when attacks are successful.

Identification

The beetle itself is small, about 1/8 to 1/3″ in length, and brown to black in color. They have wings as adults and fly from tree to tree. The noticeable symptom is the pine tree turns brown. Upon closer examination, the browning tree will have “popcorn-like” yellow mounds of sap jutting from the trees bark. These are also called “hits” or “pitch tubes.” The tree is literally pitching the beetles out using sap that flows out profusely when the cambium is damaged. It can be very effective in repelling successful attacks.

Life Cycle

MPB hatch inside of host trees as larvae that tunnel horizontally out from the mothers vertical chamber and feed in the phloem. They overwinter in the larval stage. As winter ends they continue to tunnel and feed before entering the pupal stage. Adult beetles emerge and fly to another host tree guided by pheromones released from other beetles and the trees themselves. When they find a suitable host they drill in through the bark and create a vertical chamber in the phloem. Individuals die shortly after laying eggs.

Damage

Trees that are “successfully” attacked will not survive. A successful attack implies that one or more beetles have penetrated into the phloem and laid eggs. When this happens they commonly vector the blue stain fungus which rapidly spreads through the trees cambium and chokes the vascular system inhibiting water and nutrient flow, which is fatal. The only exception is Scotch pines. Only since about 2005 have they become targets of MPB. Since then the number of Scotch pine attacked by MPB has been growing at an alarming rate. The good news is that they tend to withstand a number of hits over several years without absolute death. Many do die, but proper care will often keep mortality in check for some time.

Management

Conventional

A pesticide spray of either carbaryl or permethrin is the most tested and effective protection from MPB.

Pheromone (Non-Toxic)

This is an approach that can be effective under the right circumstances. The basic idea is that a scent (Verbenone) is released which signals the beetle that a tree (or an area) is tapped out and the beetle then turns its attention toward or a more favorable host.

The results are mixed. It seems that is fairly effective where beetle populations are low to moderate. It has no effect where populations are high to epidemic. Much of the Rocky Mountains are experiencing epidemics.

For high value trees (a tree you just can’t live without) we recommend spraying permethrin even if you are using the pheromone treatment on your property.

Cultural Practices:

The most important part of all tree care starts with cultural practices. As it relates to MPB, here is a list:

Water: Trees need water! Regardless of the season, trees need water. If it is dry out make sure the trees are getting supplemental water from a hose, irrigation system or hire a commercial company to come do it for you. Remember, just because it snows doesn’t mean there is enough water getting to the tree roots. Dig down a few inches and feel the soil. If it doesn’t stick together, then water is needed. If it is too squishy and dripping when you squeeze it then there might be too much water and it’s time to back off.

Fertilize: Many of our landscape trees do not get enough nutrients and minerals from the native soils. Consider getting on a fertilizer program, or do your homework and apply it yourself.

Remove fresh kills: MPB attacks trees in the summer (typically) which can be seen by the pitch tubes formed by the trees reaction to these attacks. Not all attacks are successful. The pitch tubes are an effective way for the tree to “pitch” the beetles out before they actually get in and harm the tree. When an attack is successful the tree will turn reddish sometime between mid fall and mid winter. These trees must be removed before April so that the overwintering larvae don’t have an opportunity to exit the tree and fly to a new tree and start the cycle again. Not only should the trees be removed but they should be disposed of properly. This means all trunk wood needs to be burned (before April!), chipped, buried (landfill), milled and the bark chipped (before April), or wrapped in plastic (tightly!). This is no joke. These beetles have been spread far and wide through firewood and logging projects.

Solar treatments can also be done. This involves heating the trees to a temperature of at least 111 degrees F under the bark. It is very labor intensive.

Thinning: Trees should be spaced properly so that they ample access to soil, water and light. When the forest is too thick, trees are competing for limited resources and many end up stressed. Have a professional make recommendations for your property.

Other Important Issues

Some other issues to consider as a tree owner are Ips Beetle, other engraver beetles, twig borers and Zimmerman Moth. For the purpose of protecting the majority of lodgepole and ponderosa pines along the lower foothills of Colorado, we are mainly concerned with Ips Beetle, which will kill trees in a hurry if attacked. The main difference when managing Ips is timing. While MPB has one generation per year the Ips can have as many as 7. They fly as early as late March and as late as November. This requires two trunk sprays timed early April and again in mid July to early August in order to appropriately protect trees.

What does this mean for you and your trees?

If you are concerned about Ips, we advise two trunk sprays timed in April and late July for your pines. If you have not seen and are not concerned about Ips in your area then once annually, mid April through mid June, will suffice.

Fire Blight

Fire Blight

Fire blight is a bacterial disease of apple, pear, hawthorn, pyracantha, mountain ash, cotoneaster, flowering quince and many other trees and shrubs. Even though it is always present in the urban landscape, the severity of new infections varies greatly from year to year depending on weather. A cool (65 degrees F), wet spring will encourage bacterial growth and we typically see a rampant outbreak. Some plants will suffer minor tip dieback while others will suffer fatal attacks.

Identification

“Shepherd’s Crook” is the infamous sign of fire blight with a blackened or burned twig tip that appears like an upside down “J”. Fruit and flowers will also be shriveled and burnt, or dry looking. Flagging branches (dead limbs with dead leaves still attached) and cankers are the most obvious signs of infection.

Disease Cycle

The bacteria enter the plant through blossoms, leaves or wounds. Initially, the bacteria emerge from the plant’s interior forming an “ooze” on the bark that insects like. It sticks to their bodies and they then carry it to blossoms where it enters the vascular system.

It can also get in via splashing water droplets that find their way through wounds from hail, pruning, insect or animal damage as well as natural openings like the stomata in leaves.

Once inside the tree, it kills the cambium and moves down the stem until it is stopped by the plants natural defenses or other intervention. Sometimes plants can wall off an attack and other times they cannot stop the attack. This has to do with the resistance of a particular variety as well as the plants overall health.

Damage

Damage is typically cosmetic and rarely harmful to plant health. Severe infestations can cause twig dieback on some plants and can be fatal in some instances. Damage is always to soft plant parts like leaves, flowers and new growth.

Management

Cultural

Annual pruning to reduce the amount of supple, new growth is desirable as it is particularly vulnerable to attack. Over fertilizing with nitrogen, especially quick release nitrogen, should be avoided.

Pruning

Often, the bacteria will move down a twig killing the cambium all the way around the trunk or branch, causing all growth above it to appear water soaked and dead. Other times, only part of the twig will be girdled and growth above the canker will appear healthy and untouched by the disease. This is a tricky situation when pruning. There is a chance the branch will survive should the infected portions be removed and there is a chance it will continue to spread if it is left. Consideration must be given to overall health and percentage of dieback from the attack.

The rule of thumb is to prune out the  entire limb if more than 50% has been girdled by the disease. If less than 50%, it can be cut out with sharp tools.

The idea of pruning trees infested with fire blight in the growing season has historically been known as a bad practice. However, this adage is somewhat misleading as trees can be pruned without leading to future problems and may even be necessary to reduce the amount of blight in a tree that could have a greater negative impact on the health of the plant if it is left intact for the remainder of the growing season. The added implementation of disinfectant tools (e.g. 70% alcohol or Lysol) in between cuts will also diminish the possibility of re-contamination.

Dormant pruning is ideal to avoid the spread of the disease. Fire blight isn’t active during this time which means it is much less likely to spread from one cut to another. However, proper pruning techniques coupled with disinfectant tools limit the potential for spread when pruning in the growing season. 

Chemical

Several sprays are available to be applied at time of blossom. The difficulty is that the flowers do not open at the same time and it’s impossible to know when an insect will be by to pollinate each flower. The best solution is to spray the flowers every few days. This can be very expensive if a commercial applicator is being used. We recommend two sprays, once the first few flowers have opened and again 7-10 days later.

A trunk injection of an antibiotic is also available and acts more as a curative than a preventative control. It is systemic, which means it will act similarly as antibiotics do for animals when ingested or injected.

Limitations include: tree health, obstruction of chemical transport inside plant (e.g. Cankers, dieback), and bacterial resistance to Oxytetracycline.

Aphids- Small, green bugs

Aphids- Leaves sticky from small green bugs

Aphids are very small, soft-bodied insects with long mouth parts that they use to pierce stems, leaves, and other tender plant parts in order to suck out plant fluids. Most plants have at least one type of aphid that feeds on it during the growing season or an off season warm spell.

Identification

Aphids are small, soft insects that are typically wingless. They are almost always found in groups or clusters of overlapping generations. They can be seen without visual aid and are easily smeared or squished when touched or if a finger is wiped across them.

Other signs include the presence of honeydew. This shiny film coats leaves and the understory of trees as aphids excrete the excess sugar they consume. Wasps, bees, and ants can often be found feeding on this sugar source. Often times, leaves turn black when the honeydew is colonized by a fungus called sooty mold.

Curled leaves can indicate leaf curling aphids which feed on leaves causing them to curl up and create a protective envelope where they are well protected from predators and foliar treatment attempts.

Life Cycle

There are many different species of aphids, some of which are host specific and others that feed on a wide host range. They produce multiple generations per year and are capable of growing their populations at rapid speed by reproducing asexually. Some females will birth upwards of 12 individuals in one day! Because of this amazing reproductive ability aphid populations can jump from insignificant to harmful levels in just a matter of a few warm days.

Once populations become too high, winged forms are produced and fly to colonize new locations. Some mate and lay eggs, which is a reliable way to survive the winter in harsher climates.

Damage

Typically, damage is minimal from leaf feeding aphids. Damage can become significant if populations spike causing leaf deformation and massive honeydew problems. This causes plants to stick to each other and promotes the growth of black sooty mold which decreases the capacity of trees to photosynthesize.

Some aphids, like the Bow Legged Fir Aphid, feed on the soft tissue of branch bark causing damage to limbs on Concolor Firs that can lead to weakened wood and possible dieback if left untreated for long periods.

Management

The best management is to help trees stay healthy and strong so they are able to defend themselves from aphids without human intervention. Proper watering and regular soil treatments help to ensure this ability.

If populations spike, a dormant oil treatment can be made before bud break in late winter or insecticidal soaps can be applied during the growing season.

There are also a number of insecticides that can be sprayed on foliage or applied systemically through the roots or trunk. The systemic applications can be applied in the dormant season and control population outbreaks for the entire growing season. It’s important to rotate pesticides if aphid problems continue to arise on the same tree. This will reduce the chance of aphid populations developing resistance to insecticides.

Bark Beetle (Ips)- Tiny holes in trunk

Bark Beetle (Ips)- Tiny holes in trunk

A group of tiny bark beetles that generally affects Spruce, Ponderosa, Pinyon and Austrian Pines. There are 14 known types of Ips beetle in Colorado.

Identification

Ips is a very small beetle, measuring 1/8-3/8 inches in length. Often, the identification is found through damage caused by the beetles. Fading and dying tree limbs are the most obvious signs.

Life Cycle

Ips begin the year as adults that start to enter trees through the bark when temperatures consistently stay above 50 degrees F. Males enter the tree first and carve out a nice chamber called a “nuptial” where they then release a pheromone to attract females. After mating, the females lay eggs in tunnels that they chew out in Y or H patterns from the main nuptial chamber. These tunnels and the main chamber are cleared of the debris that is often found in mountain pine beetle galleries. The debris is pushed out through the entrance hole and is an indicator of successful attacks because it shows up on the bark or on the ground under the tree, as saw dust or powder.

When the eggs hatch the larvae tunnel further, completing several more growth stages, until they emerge as adult beetles and exit the tree through the bark. This leaves a small round hole (about 1/8″ diameter), also an indicator of beetle presence. They complete 4-7 generations a year. The adults overwinter under the bark or in the shelter of organic matter near the base of trees.

Damage

Damage is mechanical. The extensive tunneling by the beetles and larvae girdle the trunks and limbs causing individual limbs and trunks to be cut off from nutrient and water flow, which results in partial and whole tree dieback.

Management

The best prevention of Ips attack is through cultural practices that encourage healthy growth for the trees. This includes proper watering, reduction or prevention of damage and stress, and removal of infested tree debris.

Conventional

Permethrin is recommended as a protective spray.

Boxelder Bug- Orange bugs collecting on house

Boxelder Bugs – Orange bugs collecting on house

Boxelder bugs are commonly found on boxelder and maple trees, though they also feed on other hosts and their fruit.

Identification

The body of the adult stage is black with an orange outline. However, the nymphal stage shows more orange. They feed on fruits of host trees and can cause a “catface” distortion. They become most obvious in the fall when they begin to find an overwintering spot in homes. They aggregate in large groups within and on sides of houses.

 

Life Cycle

Adults overwinter in dry areas that are protected from winter conditions such as attics, ceiling corners, voids, and other areas in houses and buildings. As temperatures warm, adults begin to seek out boxelder trees to lay their eggs. Nymphs feed on seeds and as they get bigger, move to other tree parts like leaves, flowers, and fruits. This generation will eventually reach adulthood and lay eggs, which will hatch, develop and become the overwintering generation.

Damage

Damage to trees is minimal. Adults and nymphs feed on seeds, fruit, flowers, and leaves. The main issue with these pests is their overwintering habits. They can travel hundreds of yards from boxelder trees to reach a house or building. Often times, they’ll be observed in groups on the sides of houses as well as within houses and buildings.

Management

Because they do not cause extensive damage to trees, there are not a lot of management recommendations for boxelder bugs. Keep in mind, that boxelder bugs prefer the sunny side of building and houses. There are perimeter sprays that can deter individuals from collecting on your house or building.

Codling Moth- Holes in Apples

Codling Moth- Holes in Apples

A moth that damages Apples, Walnuts, Pears and other fruits around the world. The larval (worm) phase of its life burrows into the fruit causing extensive damage and rendering the affected fruit inedible.

Identification

Usually an entrance hole can be seen on the outer layer of the fruit and often parts of the fruit will become sunken and rotten. Split the fruit open to see the tunneling and sometimes catch the larvae still inside.

Life Cycle

Codling moth overwinters as larvae inside a cocoon that is attached to bark. They pupate and emerge as adults in the spring. After they mate, females lay eggs on leaves which hatch into larvae that begin to feed on the leaves before burrowing into fruit. After they feed for 3-4 weeks, they move from the fruit to the tree to spin their cocoons. In Colorado, about 2/3 of these moths emerge to produce a second generation, whereas, the remainder go dormant and overwinter for the following season.

Damage

Damage is often extensive and will render the entire fruit crop worthless for eating. If fruit is not desired, treatment is not necessary as the pest does not affect tree health. Fruit suppression is also an option, but efficacy varies and results are inconsistent.

Management

A pesticide spray in the spring will reduce or totally eradicate infestations of this moth.

Elm Leaf Beetle- Holes in elm leaves

Elm Leaf Beetle- Holes in elm leaves

Identification

Elm leaves have many holes in them, but the veins stay intact. Larvae scrape away leaf tissue, leaving a thin layer of leaf tissue. Adult beetles are yellow with a black outline. Larvae are worm-like with yellow and black segments. Yellow egg masses can sometimes be seen on leaves.

Life Cycle

Adults emerge in spring after spending the winter hiding in protected areas. They feed and mate, at which time their wing color changes from green to yellow. They begin to lay egg masses on leaves several weeks after mating. Larvae hatch and begin feeding which ensues for about 3 weeks. Larvae crawl to the trunk to find a pupation site. After adults emerge, individuals either mate and produce a second generation, or move to an overwintering location.

Damage

Damage is caused by both adults and larvae. Adults chew holes through leaf tissue, but leave leaf veins intact. Larvae also feed between leaf veins leaving a thin layer of leaf tissue behind which creates transparent spots in leaves.

Management

There are multiple systemic applications and foliar sprays that can be made to manage elm leaf beetle. Trunk banding (insecticide contaminated band) can also be an effective control since larvae crawl down the trunk to pupate.

See the link below for more information on elm leaf beetle:

http://www.ext.colostate.edu/pubs/insect/05521.html

Eriophyid Mites

Eriophyid Mites

Eriophyid mites are more closely related to arachnids (spiders) than insects. They are microscopic and cannot be seen with the naked eye. They are noticed by the abnormalities created in soft plant tissues when they feed. Commonly Affected Trees: Green Ash, Cottonwood, Poplar, Maple, Plum, Cherry, Privet, and Catalpa. Honeylocust rust mites are a type of Eriophyid mite that causes an orange tint to leaves and is common on honeylocust.

Identification

A hand lens microscope can be used to identify these critters. However, it is very difficult to differentiate between species using this method.

Eriophyid mites are easily identified by the signature mutations each species causes within its host plant. As the mite feeds by piercing and sucking the soft cells, it introduces a growth regulator through its saliva into the plant tissue, which then induces a desired reaction from the plant. This reaction or mutation then acts as food and protection for the parasite. Most are host specific, which means that each species of Eriophyid mite has one type of plant that it lives its life in and cannot reproduce within another plant system.

There are basically five types: Bud, Flower, Rust, Gall, and Blister.

Life Cycle

Eriophyid mites overwinter as females in a hardened state either underneath the bark or in bud scales. In the spring they lay eggs which hatch after fertilization and then go through three more stages: nymph 1, nymph 2 and adult. They have multiple generations per year, usually 3 or 4, with some generations being all female which is then followed by a generation with males.

Their physical structure is elongated with 2 pairs of legs which are near the head. They have a very difficult time moving on their own and depend on wind, insects or birds to carry them to a new host.

Damage

Damage is typically cosmetic and rarely harmful to plant health. Severe infestations can cause twig dieback on some plants and can be fatal in some instances. Damage is always to soft plant parts like leaves, flowers and new growth.

Management

Control of this pest is fairly easy. Removal of infected plant parts is essential, but not always practical for control. If the problem is aesthetically displeasing there are a few effective sprays that can be used:

A pesticide called Carbaryl applied in mid-spring as the buds break should give season long control. It may be necessary for 2-3 seasons and then monitoring for new outbreaks thereafter should suffice.

A dormant oil in the fall just before leaf drop will give a fair control over the next year’s 1st generation of this pest. This should be repeated the following season with several horticultural oil sprays to continue smothering adults that will reproduce (probably 3-4 times during the growing season).