Aphids are insects that attack a wide variety of trees and shrubs. Aphids are commonly found on Ash, Elm, Walnut, Willow, Cottonwood, Aspen, Apple, Linden, Snowball bushes and many other ornamental trees and shrubs. Aphids first start to appear in spring to early summer, and can reproduce quickly depending on environmental conditions. An aphid population can increase in numbers very quickly.

Aphids are tiny, soft-bodied insects that are found clustered together on the leaves of trees and shrubs. The leaves may appear to be curled, thickened or discolored. Damage occurs when the aphid sucks the juices out of the leaves. Since they are unable to fully digest all of the sugars in the plant sap, the insect secretes the excess in a liquid called "honeydew" which often drips onto leaves, branches, trunks, cars, sidewalks, patios, etc. A sooty mold may develop on the honeydew causing those surfaces to appear dirty. Ants feed on the honeydew and are often present in the areas that aphids are found.

Some Aphids spend their entire life on one plant while other go from plant to plant. Aphids that hatch from over-wintering eggs are wingless females that give birth to live aphids and can produce many generations throughout the summer. Some aphids are born with wings so that they can travel to less populated hosts. In the fall, the female aphid lays eggs in the bark for over-wintering.

Aphids should be sprayed at the first sign of an infestation. This should be done with an insecticide such as Astro, Talstar, or Orthene. A certified arborist can also systemically inject a tree to control the present generation of aphids or to provide season long control, which should be done in the spring of the year.

Repeat applications may be necessary as reinfestation can occur. A follow-up application may be necessary as early as 21 days, as spraying only control aphids present at the time of application.

 

SYMPTOMS AND SIGNS

Apple Scab is a disease that is found on both apple and crab apple trees. Symptoms of Apple Scab include dead spots on the leaf usually found along the leaf mid rib or along the veins. The spots start out as an olive green color and continue to darken and enlarge throughout the growing season. Depending on the conditions when the fungus forms, the spots may even have a velvety appearance. As the disease continues, the leaf may appear to be chlorotic due to lack of food production or the leaf may even dry up and drop off. The fungus may also infect parts of the flower and the fruit as well as the leaf tissue.

LIFE CYCLE

The Apple Scab fungus over-winters in fallen leaf debris. In the spring when the over wintering spores release they become airborne and spread by the wind. A thin film of moisture attaches the spores that land on the newly emerging leaf. Fungus spores that are attached to the leaf need periods of high humidity in order to continue to grow. Prolonged periods of leaf surface wetness, along with high relative humidity favor the development of Apple Scab.

CONTROL

Apple Scab is most effectively controlled in the spring of the year as the new leaves are beginning to form. Repeat applications with a fungicide containing Captan, Eagle, and Banner Max, and labeled for application on apple trees is most effective. These applications are needed in order to reduce the number of scab lesions. Preventative applications are necessary if the conditions favoring Apple Scab development are present in the spring. If there are relatively dry conditions in the spring, there may be little or no Apple Scab present.

 

 

Ash Borers

Dothistroma Blight is a devastating foliage disease that attacks Ponderosa and Austrian Pine trees in the Billings area.

SYMPTOMS

Dothistroma Blight symptoms are first observed in a color decline of the pine trees. Close observation of the needles indicates tan, brown, or reddish spots. Greenish bands are present on the needle, then turn to reddish colored bands as the disease progresses. The needle progressively turns light green, tan, and then brown with the base of the needle remaining green. Infected needles drop prematurely. Newly emerged needles are infected any time it rains from June to October.

Dothistroma is most often observed in native stands of pines that have had their environment altered by construction, change of drainage, soil ph altered, compaction, grass planted over root zone, etc. Unthrifty Ponderosa trees may not show stress from construction or landscaping for a number of years after they have had their environment altered.

TREATMENT

Ponderosa Pines that have been diagnosed with Dothistroma should be systemically injected with a fungicide in early June to protect the new growth that is emerging from the candle. Should a spray program be selected, apply Daconil 2787 every two weeks through the candling period (early June, Mid June, early July).

To enhance vigor of the diseased tree, fertilization is recommended at the time of the systemic injection or root fertilization in the fall or very early spring.

If the diseased tree stabilizes or shows improvement, the preceding recommendation should be repeated for two to three years or longer to insure recovery of the tree.

 

Dutch Elm Disease is a systemic vascular wilt disease caused by a fungus. Dutch Elm Disease predominately attacks the American Elm in the upper great plains.

SYMPTOMS

The earliest symptoms are yellowing or wilting of the leaves on single branches in the upper crown. The yellow or wilted leaves quickly turn brown and die. This condition spreads rapidly, one branch at a time, to progressively larger branches and soon is distributed throughout the crown. Symptoms appearing in late spring usually mean the tree will be dead by the end of the summer, larger trees, however, may take several years to die. Symptoms beginning in mid summer usually mean the disease will only progress to a few branches. The next year, however, the disease will progress no further during that season, and the tree often remains free of the symptoms the next season. Infected branches contain brown discoloration in the outer xylem.

DISEASE CYCLE

The Elm Bark Beetle carries the fungus from infected wood to healthy trees. These insects lay their eggs in dead or dying elms. In late fall the eggs hatch and produce larvae, which tunnel under the bark. In early spring, they emerge as adults. The fungus produces sticky spots in the larval galleries. These spores are picked up on the body of the beetle as it emerges from the tree. The beetle carries the spores to healthy trees as it feeds. Infection also occurs through root grafting.

PREVENTION

The preferred method is to prevent infection of a healthy tree. This is done with an annual application of Alamo by a trained arborist. A prevention application of Alamo can be done any time during the growing season but preferably in the spring when leaves are developing on the tree. To maintain a healthy tree, a fertilization program is recommended with proper pest control.

CONTROL

Control of Dutch Elm Disease can only be done in the early stages of the disease. If a diagnosis is made with 25% or less infestation of the tree (preferable 10% or less), the following control measures must be taken. An application of Alamo at the therapeutic rate should be done as soon as possible. The infected part of the Elm needs to be removed and taken from the premises. An annual application of Alamo at the preventative rate needs to be done- preferably early spring.

 

Elm Leaf Beetles feed on Siberian or Chinese Elms. The adults lay yellow egg masses on the bottom of the leaves. The first generation emerges approximately the first to MID PART OF JUNE. The eggs hatch and the larvae feed on the leaves, leaving a brown area between the leaf and veins. The second generation hatches about late July or early August. The damage done to the trees by the feeding of the larvae will not kill a tree by itself but will cause the tree to go into a state of decline allowing other diseases such as canker, wet wood, and Verticilium Wilt to kill the tree.

Controlling Elm Leaf Beetle larvae is done by spraying the tree to control the first generation and again during the second generation. If spraying is not possible, injection can be done during the first generation and will control both generations.

In the fall the adult beetles invade the home to spend the winter hibernating in the attic, walls, insulation etc.

In late winter and spring they often roam the house with no special purpose. Many times the homeowner will have severe infestations. To control the winter infestation inside the home, the following must be done:

• Control the Elm Leaf Beetle in the larvae stage on the trees with spraying or injection. 
• An outside perimeter spraying in October to kill many of the invading pests before they enter the home.
• Place pest strips in the attic in late September.
• Should the population be severe inside the home late winter or spring, use timed-release dispenser to control roaming adult beetles.

Elm Leaf Beetles need to be controlled or repeated infestation will cause the tree to decline in health and allow large populations of the beetle to be available in the fall to invade the home. Fertilizer injection or liquid soil fertilization will enhance the vigor of trees that have had infestation.

 

 

  

Fireblight is a bacterial disease spread from tree to tree during blossom by pollinating insects, birds, and raindrops. Fireblight infects apple trees, ornamental crabapple trees, pear trees, Mountain Ash, Cotoneaster, and other various ornamental trees.

Symptoms of Fireblight are die-back of infected branches from the outer tip inward. The leaves appear to have wilted and dried on the branch and remain attached (leaves and fruit appear to be scorched by fire for Fireblight). The twigs and branches will be discolored, blackened, and dying. Symptoms start to appear shortly after petal fall and continue until mid summer. Fireblight bacteria will over winter in infected twigs and branches.

After diagnosing Fireblight, the infected twigs and branches must be pruned out of the tree. Infected branches need to be pruned approximately six inches into the uninfected part of the branch. Pruning tools must be disinfected between each cut (a 2% Clorox solution or other quality disinfectant will work). Pruning is the only solution for trees bearing edible fruit. Ornamental trees should be pruned after diagnosed with Fireblight in the summer and injected with Oxytetracycline in the fall or early spring by a professional arborist. A quality fertilization program is recommended for ornamental trees in late fall or early spring to increase the health and vigor of the tree.

On edible fruit trees two to four sprays with streptomycin done every five to seven days during pre-blossom and blossom is required to prevent infection of the tree. Timing of application is most critical.

Ornamental trees require a preventative injection early spring before or at pre-blossom. A fall injection with Oxytetracyline works very well for prevention of Flireblight the following spring.

Always select Fireblight resistant varieties when purchasing plant species that can be infected with Fireblight.

 

 Return to Pest List

As its name suggests, the honey locust plant bug attacks the Honey Locust tree. The adult bug is light green to yellow and has a four segmented antennae and a beak-like mouthpart. Eggs are laid under the bark and hatch when the buds of the leaves begin to open. The nymphs then crawl onto the leaves of the tree to feed. If the infestation is extensive, complete defoliation can occur.

Some years the threshold of insect attack is small and the tree survives the infestation without harm. For the years when the infestation is heavy, damage can result quickly causing the tree to lose vigor and become weak which then results in winter injury. Timely applications are necessary for this pest.

Chemical application control includes spraying at the time of infestation, chemical trunk injection at the time of infestation or using a chemical soil drench application prior to infestation. The soil drench application technique of control is easily done in the fall with control lasting through the next growing season.

 

 

  

Pine Bark Beetle and IPS Engraver Beetle attack and kill pine trees and other species of long needle evergreens that have been planted or are naturally grown in a landscape setting around homes.

The IPS Beetle attacks long needle pine trees of various sizes in the spring and has multiple flights through the season. The Mountain Pine Beetle attacks all species of pine trees in the latter part of July and August. Both species of beetles are devastating to a tree that is not in the healthiest of condition.

The most susceptible trees are the ones that have had alterations made to their environment by construction within the last ten years; for example root damage, fill added over root systems, natural water drainage rerouted and grass planted and maintained underneath the trees. Trees affected with construction alterations are generally the most aesthetically valuable trees to landscape settings. Drought, fire damage, and over-population also weaken valuable trees.

To maintain valuable pine and spruce trees the following steps should be taken:

• Identify which trees have great aesthetic value to your property.
• The valuable trees should be deeply watered twice a month during the growing season. Lawn watering will not suffice.
• Your transplanted or small natural trees should be deep root fertilized in the fall or early spring until they reach maturity. Fertilize mature trees every two to three years to maintain a healthy tree. Lawn fertilizing is not adequate.
• Valuable trees should be sprayed every year with Onyx or Astro per label directions. These spray residuals are restricted for use by professional licensed applicators and will protect the trees through the entire growing season. Spraying for prevention of Bark beetle or IPS Beetle is imperative after any type of damage is done to a healthy tree, for example construction, car hitting tree, drought, etc. Systemic injection of fertilizer will increase the vigor of unthrifty or construction damaged trees.

If your trees have had a beetle attack:

• When beetle damage is diagnosed during the summer or fall, the tree should be injected by a certified applicator with Metasystox R to kill the larva underneath the bark.
• The tree should be deeply watered (unless too much moisture due to poor drainage has weakened the tree) and deep root fertilized in the fall or early spring.
• The tree needs to have a preventative spray applied the next spring, plus the preceding standard prevention measures taken.

It will take 50 to 100 years to replace a mature Ponderosa Pine tree in your landscape.

 

 

Maple Tree Decline 

Hard-bodied scale is also called Oyster Shell scale due to the resemblance it has to an oyster in the adult phase of its life. Scale attacks many woody plants such as maple, ash, aspen, lilac, dogwood and others. This pest causes damage to the tree by attaching itself to the bark and sucking the sap out of the tree. If infestation becomes severe damage or death to the tree can occur.

This scale produces one generation per year and overwinters in the egg stage. It then hatches in the spring and quickly attaches itself to the plant to feed. The mother scale is about 1/8-inch long, brown or gray, slightly banded, and the general shape of an oyster shell. The overall appearance of the scale often is similar to that of the underlying bark and these insects are easily overlooked.

Oyster shell scale can be hard to control because of the thick shell they build around themselves. However, this scale can be treated with a spring trunk surface application of a restricted use ornamental chemical called Safari. Scale can also be treated by the application of a highly refined horticulture oil applied to the crawling stage of the scale life cycle. This control needs specific timing of the application to the crawling life cycle. Repeat applications may be needed to control late outbreaks of the crawling stage.

 

 

Spider mites are common pest problems on many plants around yards and gardens in Billings. Injury is caused as they feed, bruising the cells with their small, whip-like mouthparts and ingesting the sap. Damaged areas typically appear marked with many small, light flecks, giving the plant a somewhat speckled appearance.

Following severe infestations, leaves become discolored, producing an unthrifty gray or bronze look to the plant. Leaves and needles may ultimately become scorched and drop prematurely. Spider mites frequently kill plants or cause serious stress to them.

Many spider mites produce webbing, particularly when they occur in high populations. This webbing gives the mites and their eggs some protection from natural enemies and environmental fluctuations. Webbing produced by spiders, as well as fluff produced by cottonwoods, often is confused with the webbing of spider mites.

Honey Locust, particularly those in drier sites, are almost invariably infested with the honey locust spider mite (Platytetranychus multidigituli). Other mites may affect shade trees such as elm, mountain ash and oak.

Most spider mite activity peaks during the warmer months. They can develop rapidly during this time, becoming full-grown in as little as a week after eggs hatch. After mating, mature females may produce a dozen eggs daily for a couple of weeks. The fast rate of development and high egg production can lead to extremely rapid increases in mite populations.

Dry conditions greatly favor all spider mites, an important reason why they are so prevalent in the more arid areas of the country. They feed more under dry conditions, as the lower humidity allows them to evaporate excess water as they excrete. At the same time, most of their natural enemies require more humid conditions and are stressed by arid conditions. Furthermore, plants stressed by drought can produce changes in their chemistry that make them more nutritious to spider mites.

Water Management: Adequate watering of plants during dry conditions can limit the importance of drought stress on spider mite outbreaks. Periodic hosing of plants with a forceful jet of water can physically remove and kill many mites, as well as remove the dust that collects on foliage and interferes with mite predators.

Chemical Controls: Chemical control of spider mites generally involves pesticides that are specifically developed for spider mite control (miticides or acaricides). Few insecticides are effective for spider mites and many even aggravate problems. Furthermore, strains of spider mites resistant to pesticides frequently develop, making control difficult. Because most miticides do not affect eggs, a repeat application at an approximately 10 to 14 day interval is usually needed for control.

 

 

Spider Mites of Evergreen 

White Pineweevil, Pissodes strobe (Peck), is a serious destructive insect pest of spruce trees in Montana with either forked or deformed trees resulting from repeated infestations. Spruce trees of any heights are susceptible to attack.

The adult white pine weevil is a long reddish-brown weevil with white patches on its wing covers. Like most weevils, the adult has a long snout-like beak from which knobbed antennae arise. The larvae, which live beneath the bark, are white, legless, with a distinct brown head and 5/16" long when mature.

The adults over-winter in the duff under trees. In Mid-March to mid-April adult females climb trees to feed on leaders. Females lay one to five eggs in the feeding wounds in tree leaders. The eggs hatch in about a week and the larvae feed just below the bark tunneling downward, girdling and killing the shoot as they go.

Symptoms: The first symptom evident from attack by the white pine weevil is glistening droplets of resin on terminal leaders in late March and April. This is the result of punctures made by adults in the process of feeding and cutting egg-laying sites. The larvae do the most damage as they tunnel downward in the leader, causing the shoot to wilt and eventually die. Repeated infestations in successive years result in a deformed or forked tree.

Biological Control: Natural enemies do not provide adequate control.

Mechanical Control: Prune infested leaders. As soon as the leader droops, prune the leader out just below where the bark discoloration stops. Remove the pruned leader containing the larva from the site. Corrective pruning of the injured top involved removing all but a single shoot (one of the largest) at the topmost healthy whorl. This promotes healing, resumption of vertical growth and straightening of stem form.

Chemical Control: Spray only the leader with a registered insecticide in the spring before the adult feeding is observed (late-March through April).