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Seasonal Topics:   Summer's End Edition
September 8, 2009

Walnut Twig Beetle & Thousand Canker Disease More >
Fire Blight More >
Mountain Pine Beetle
More >

Ash Decline More >
Turf diseases to look out for More >
  Mountain High Tree,
Lawn & Landscape

5717 W. 11th Ave.
Lakewood, CO, 80214


Walnut Twig Beetle and Thousand Canker Disease

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Care Walnut Beetle Care
Tree Care Tree
Care   Walnut Twig Beetle  

Many people in Boulder will attest to the destructive nature of the Walnut Twig Beetle. Adult beetles travel from April to September, and are so small they often go unnoticed. Damage can be extensive when the population of the beetle reaches into the hundreds and thousands. Adding insult to injury, the adult beetle also carries a virulent disease known as Thousand Canker Disease. This pathogen causes large vascular cankers to form underneath the bark. Movement of water and nutrient resources comes to a standstill and large limbs begin to dieback quickly. Over 700 Walnut trees have been removed in the Boulder area due to this beetle and pathogen combination in the past few years. We tracked the movement of this pest into northwest Arvada last year, and into Cherry Hills and Englewood this year. Walnuts throughout Denver were attacked last year, and are now quickly declining.

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Care Walnut Twig Beetle and Thousand Canker Disease Care
Tree Care Tree
Care   Walnut Twig Beetle and
Thousand Canker Disease

Current programs are available to help prevent an attack. Programs include multiple trunk applications, as well as soil injections of insecticides. If we stay vigilant with removing attacked and diseased trees there is a hope to save some trees. Some small communities are even organizing a tree inventory to identify where the Walnut trees are and to spread awareness of the problem. If you or your community would like information or help in developing a program, please let us know.

Fire Blight
(by CSU Cooperative Extension)

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Care Fire Blight Care
Tree Care Tree
Care   Fire Blight  
    Tree varieties with some degree
of fire blight resistance:

Early McIntosh
Golden Delicious
Missouri Pippin
Red Delicious

Golden Kieffer
Red Splendor
Snow Cloud
 Spring Snow
Fire blight thrives in warmer, wet weather when the disease-causing bacterium becomes active. Apple, pear, quince, crabapple and mountain ash, but NOT GREEN or AUTUMN PURPLE ASH, commonly are affected. The bacterium oozes out of cracks and crevices in the bark, and bees or other pollinating insects pick it up on their bodies. The disease spreads as these insects pollinate other flowers.

If your trees are affected by fire blight, they will begin to show symptoms just before their flower petals fall. This is the blossom blight stage when flowers begin to turn brown and mushy and wilt. Eventually, the bacteria will move down into the branches and leaves of the tree. Leaves darken and wilt but remain attached to the tree (see above), giving it a scorched or burned look. Branch tips blacken and curl, causing a "shepherd's crook" symptom.

Fruit also can be affected. Bacteria often oozes out of the infected fruit and, as symptoms progress, fruits remain attached to the tree as shriveled "mummies." Cankers, which are sunken areas darker in color than the surrounding bark, form as the disease progresses. If present on the main trunk, cankers often are fatal, as they eventually will girdle the tree.

Cankers also serve as the overwintering source of the bacterium. The following spring, bacteria will ooze from the cankers or cracks in bark. Insects may come in contact with the ooze and spread the disease to other trees.

Fire blight Control

Fire blight control can be a challenge. A variety of controls are available and success usually is greatest when we integrate all of them.

The use of resistant varieties is the first line of defense. Listed on the table above are apple and crabapple trees with certain degrees of resistance to the blight. Resistance doesn't necessarily mean immunity. A tree with resistance can become infected, but the problem won't be nearly as severe as if there were no degree of resistance.

Avoid overfertilization with nitrogen. Nitrogen stimulates new growth and the new growth is highly susceptible to fire blight infection.

Practice sanitation when pruning trees. Prune out and destroy all infected and dead plant tissue. Make pruning cuts 6 to 12 inches into healthy tissue. Always treat tools in a disinfectant solution, such as 10 percent household bleach or a disinfectant spray, between each cut to minimize disease spread. Prune newly infected twigs as soon as possible in the spring. Do all other pruning during winter.

Chemical treatments include either foliar applications using a copper hydroxide material, or a trunk injection of an antibiotic similar to those we take for infections.

Mountain Pine Beetle

New attacks from Mountain Pine Beetle have been found in Scotch, Pinon, and Mugo pines throughout the Denver metro area. I have personally found trees that were attacked in Denver, Lakewood, Arvada, Aurora, Cherry Hills Village, and Englewood. Many of the attacks on Scotch pines have been unsuccessful in producing larva, but this can quickly change if trees become stressed from other factors such as drought or storm damage. Monitoring and quick responses are extremely helpful in containing epidemic pest outbreaks. The infamous nature of this insect in Colorado should further reinforce the need to be aggressive in fighting Mountain Pine Beetle. Please let us know if you find possible hits on trees and need help with identification.

Ash Decline

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Care Ash Decline Care
Tree Care Tree
Care   Ash Decline  
When several factors combine to cause stress and deaths in a tree species it can be labeled as a “Decline Complex”. This tag has been assigned to several situations in the past twenty years, including Sugar Maple Decline Complex in the eastern United States. Damaging agents such as drought, vascular diseases, advanced age, and internal wood decay combined to cause the death of several thousand Sugar Maples in Pennsylvania, New Jersey, and Maryland. A similar situation appears to be arising in our Ash trees. Over the past sixteen months we have noticed a remarkable number of Ash trees showing tremendous amounts of branch dieback. These same trees have suffered from several years of sustained drought, extremely large seed crops, and two different pathogens, and attacks from the very damaging Ash/Lilac borer. Arborists and university professionals are working together to gather more information in order to form a true diagnosis. In the meantime, we are treating each case symptomatically. In other words, if a tree is being attacked by the borer then we will treat it with insecticide trunk applications. If we find root loss from drought, then we will use deep root watering and supplemental irrigation to make up the difference. If you notice that your Ash trees are struggling, don’t ignore it! Let us know and we can try to help.

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Turf diseases to
look out for

Tree Care Tree
Care Necrotic Ring Spot Care
Tree Care Tree
  Necrotic Ring Spot.  

Necrotic Ring Spot and Ascochyta Leaf Blight

This summer has left its impression on many areas of our lives. The frequent and harsh hail storms have smashed windows, broken siding, and dented cars. The plentiful rainfall has helped many trees to flourish. The moderate temperatures have allowed many people to sit back and enjoy a lazy summer. However, one thing that seems to have been overlooked by many people is the health of their lawn. The added moisture this season, in combination with the moderate temperatures, has allowed for two specific pathogens to decimate many lawns throughout the Denver metro area. Necrotic Ring Spot

Tree Care Tree
Care Example of Ascochyta damage. Care
Tree Care Tree
  Example of Ascochyta damage.  

SYMPTOMS: Areas of dead circles will develop first in shady areas and then move out into sunny areas. A tuft of green grass is often seen still alive and viable inside the dead circle of grass

Begin a fungicide treatment regimen in the spring
• Use disease resistant varieties of Kentucky bluegrass to seed and regrow grass in dead areas
• Maintain proper watering practices; don’t overwater and irrigate during the early morning hours rather than in the evening


SYMPTOMS: The affected areas will be straw colored. Individual blades start dying back from the tips causing a “pinched” appearance starting at the top. Ascochyta’s appearance can vary from non-uniform patches to streaky. Wheel tracks from the lawnmowers will often be evident moving the straw appearance thru the otherwise green turf. WHAT IS


• Maintain a properly balanced fertilization program
• Core aerate in spring and fall to reduce thatch buildup
• Keep mower blades sharp
• Mow to a height of 2.5 to 3 inches. Never mow more than 1/3 off the blade height at one time.
• Do not mow when turf is wet
• Water in the morning so the leaf blades can dry quickly
• Water lawn deeply to a depth of 5 to 6 inches but water less frequently. Do not over water as this can worsen the disease.


During most summers voles will move into wild or native areas and feed on fast growing grasses and small shrubs. However, this year we have seen active burrowing in turf areas throughout the entire summer. The voles use the burrows that they create in the turf to protect themselves from predators. The grass surrounding the burrows will eventually die, leaving a horribly disfigured lawn with meandering dead areas near many of the flower and shrub beds. The junipers have also been unsuccessful in escaping the summer unscathed. As junipers beds get older they will accumulate a vast amount of debris from years of dead needle and twig tissue. The voles use these areas within the depths of old juniper beds to conduct their activities. The voles will feed on and girdle the branches, causing them to die. The results are unmistakable.

There are programs designed to control vole activity, starting with good old fashioned shrub cleaning and pruning. The idea is to open up the interior of the shrubs enough to make the voles vulnerable to predators. Predators are a great form of control and efforts should be made to maintain the natural predator population of foxes and predatory birds. As winter approaches the cover for the vole turns from shrubs to snow cover. Deep snows provide ample cover for the voles, but a properly administered baiting program can help to control voles year round. Please contact one of our representatives for help in developing a program that works for you.

Recycled Mulch

We Recycle We recycle.

Mountain High Tree, Lawn & Landscape  | 5717 W. 11th Ave. | Lakewood, Colorado | 80214 | 303.232.0666
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