Spraying trees is an effective way to provide immediate relief from harmful insects

Certain preventative sprays are designed to act as a barrier for insects or to protect from diseases that can be spread from tree to tree.

What can Arborcare do for me?

While many tree and shrub health care problems can be remedied through cultural means such as proper irrigation and fertilization when plants do become distressed with insect problems. Arborcare can make available the most environmentally friendly methods to help control them on your property. Arborcare offers a wide variety of tree and shrub spraying treatment options that are designed to target specific pest and disease problems.

Dormant oil

What is dormant oil and how does it work?

Horticultural oil, often referred to as dormant oil, is a highly refined oil that has been used since the 1800’s to control insects on trees and shrubs. Horticultural oil is environmentally safe, and non-toxic to pets, animals, and children. Unlike other pesticides, oil, when properly applied, will do its work in less than 10 minutes, leaving no active residue in the plants.
Oils are a mechanical control that works by suffocating insect egg masses laid in the bark and twigs of trees or shrubs that overwinter on the plant. It also works on scale insects by coating the outer scale surface and not allowing oxygen to get inside to the actual insect. Applied during the dormant season, late fall or early spring, it’s a good way to reduce insect populations before the next growing season begins, reducing further pesticide use later on. Oils can sometimes be used during other parts of the year to control other stages of insect growth, but its application is heat dependent. With the high temperatures we encounter through most other parts of the growing season, the use of oils other times of the year here in Utah is often limited.


Fungus, Blight, and Powdery Mildew

How can I tell if I have fungus on my trees?

Fungal problems typically affect leaves, needles, blossoms, and twigs of trees and shrubs. Left untreated, some of the typical diseases can progressively get worse and possibly lead to death. Proximity to already infected plants is often one of the main factors contributing to the spread of the disease.
Probability of infection can also sometimes be related to environmental conditions such as cool, wet weather. Stress can also play a role in susceptibility. The more stressed the plant is, the less likely its defense mechanisms will be able to help prevent the spread of the disease. In our area, most of these problems actively spread in the spring, although visible symptoms may not appear until later in the year.
Symptoms of common fungus problems include black spots on the leaves (aspen leaf spot fungus), brown to black spots on leaves and fruit (scab fungus), disfigurement and necrosis of leaf tissue (anthracnose), circular holes in leaves (coryneum blight), externally growing white mold on leaves (powdery mildew), spots/banding/discolored tips on needles (tip blight fungus), and discoloring and sloughing of needles (needlecast). Fireblight is the main bacteria related problem in our area. With fireblight blossoms will often turn brown and fall off early, then later the new leaf and twig growth shrivels, turns black, and often curls or droops but remains on the tree.
Depending on the situation, severity of damage, and type of disease, sometimes pruning off effected branches is recommended. The majority of these diseases can be sprayed for preventatively in the spring, powdery mildew sometimes requires additional late summer/early fall sprays, and some can be sprayed for as a sterilization measure in the fall.

Common fungus and bacteria problems in our area (Utah)

  • Leaf spot fungus – aspens, ornamental plums (trees and shrubs)
  • Scab fungus – apples, crabapples, and pears
  • Anthracnose – sycamores, London planes, maples, and native scrub oak
  • Coryneum blight – apricots, peaches, nectarines, cherries, and flowering cherries
  • Powdery mildew – apples, crabapples, euonymus
  • Tip blight fungus – pines
  • Needlecast fungus – spruce and firs
  • Fireblight – flowering pears, crabapples, mountain ash, pyracantha, and roses


Common harmful insects in our area (Utah)

Spidermites and Root Weevils

  • Spidermites are extremely small (barely visible) eight legged arachnids
  • Common hosts for spidermites include Alberta spruce, junipers, honelylocusts, fruit trees, and many shrubs especially burning bushes
  • Common hosts for root weevils include privet, euonymus, laurels, and lilacs
  • Spidermite symptoms and signs include dusty appearance on leaf surface, small thin webbing under leaf, dieback.
  • Root weevils eat notches on leaf edges and damage root systems.

Bark Beetles and Borers

Bark beetles and borers are insects that tunnel inside the woody material of a tree or shrub. Some, such as the Ips bark beetle tunnel just underneath the bark and stay exclusively in the cambium layer, or conductive tissue, of the tree. Others, such as the Ash/Lilac borer start in the cambium layer then continue tunneling deeper into the sapwood of the tree. Some borers, such as the Pine pitch tube borer have very evident entry holes in the lower trunk of the tree, making early detection more easily possible.
With these types of borers sap or frass coming out of the entry hole is usually present. Others, such as the bronze birch borer, start in the top of the tree and are not usually noticed until a branch or section in the upper crown of the tree starts to decline and die. At this point the exit holes in these branches become noticeable and sawdust comes out instead of sap or frass. The majority of beetles and borers are attracted to and attack trees that are already stressed for other reasons, often water, soil, nutrient, or root related problems.
Keeping trees as healthy as possible is often one of the best ways to help aid in prevention. There are some, however, that are just perpetual problems and will attack even healthy trees. Some types of beetles and borers can be controlled after they have entered a tree, others will kill the tree once they enter. Various sprays and systemic treatments can often be performed for either control or prevention depending on the type of tree and insect. The tree should be evaluated for its general health, amount of damage already sustained, or potential risk of infestation in order to determine the proper treatment plan.

Common beetles and borers in our area (Utah)

  • Ips bark beetle and turpentine beetle – Evergreen trees such as spruce, pine, and fir
  • Pitch tube or pitch moth borer – pine
  • Engraver beetle – fir
  • Cherry shot hole borer – cherry and other stone fruits
  • Ash/Lilac borer – ash and lilac
  • Bronze birch borer – all species of birch
  • Locust borer – black, Idaho, and Purple Robe Locusts
  • General roundheaded and heartwood borers – maple and apple
  • Peachtree borer – peach and nectarine
  • Aspen borer – aspen and other poplars
  • Elm bark beetle – elm


Scale insects appear as bumps, have a hard or soft covering, are immobile at maturity, and are plant genus specific. Plant hosts include apple, pine, maple, elm, sycamore, euonymus, etc. They damage the plant by sucking the plant fluid.


Aphids are soft bodied insects that vary in color and are very small (1/16″ to 1/4″). They host most plants including roses, maple, linden, fruit trees. The damage plants by sucking the plant fluids and can leave a sticky, shiny honeydew residue.

Other insect treatments include

  • Fruit tree sprays to help prevent wormy fruit or diseased, damaged fruit
  • Gall forming insects
  • Snail and slug control


Example of a spray to a large tree