What Tree & Shrubs diseases and Insects are there?

What Tree & Shrubs diseases and Insects are there?

Acecaps
These are small capsules that are inserted into the trunk of the tree in early May. As the sap moves upward, small amounts of the insecticide are taken up to the upper parts of the tree. When the insects take a bite, the insecticide in the sap kills them. Acecaps can be used every other year. No spraying is necessary. The capsules are easy to handle and safer than other methods. Acecaps will also reduce the number of aphids and other insects such as caterpillars.
Acecaps put the insecticide right into the tree trunk. None is dispersed into the air. Thus there will not be stray pesticide on cars, toys, lawns or walkways.
Birch Tree Care
Birches are popular landscape trees. Its bark texture and colour make them highly attractive landscape specimens. Two major insects affect this beautiful tree. One is the Birch Leaf Miner and the second is the Bronze Birch Borer.
In the urban environment, birch can be stressed and can become susceptible to a devastating insect, the bronze birch borer.
The Bronze Birch Borer adult is a slender, metallic-coppery beetle about 3/8 inch long and rarely seen. The larvae occur beneath the bark, and are white, segmented, legless grubs with an enlarged area behind the head. They are about ? inch long when mature. The larvae feed in the plumbing (phloem) of the birch just below the bark. The feeding reduces the food sent to the roots. Decreased root growth and function leads to inadequate water and the tree begins to die back, often starting with the upper crown.
Often, foliage on some branches in the upper crown begins to yellow in midsummer, progressing to dead brown leaves. This results in the death of smaller branches. Later larger branches begin to die and the entire tree may eventually die. Ridges may be seen on the bark of the tree due to the larval tunnels beneath the bark. Adult beetles emerge mid to late June. Eggs are laid in cracks or crevices in the bark. The larvae emerge and enter the wood.
Borers seldom attack healthy, vigorous trees. The keys to keeping birches healthy:
Select a location where the roots will be cool and moist, but where the leaves receive full sunshine.
Sufficient watering is the most important factor in maintaining a healthy birch tree. During the growing season a, slow (2-3 hours), deep (8-18 inches) watering once per week is recommended.
Mulching over the tree’s root system will moderate soil temperatures and keep the soil moist. Ground covers will also keep the soils moist and cool
Fertilizing is beneficial to ensure that nutrients are not lacking.
Pruning should be avoided from May 1 to July 1. Female borers appear to be attracted to fresh pruning wounds.
Preventative treatments of insecticide on the bark can reduce the larval population if applied in late June and mid July. Other methods may also be available – please contact us for details.
Birch Leafminer
The larvae of this sawfly make the leaves of birch trees blotchy with dead tissue. The larvae feed between the top and bottom layers of the leaves. The damage causes the tree to look dead with wilted, brown leaves. The damage forces the tree to refoliate. This reduces its ability to produce food for growth. The damage may also make the tree more susceptible to borer attack.
Birch Leafminers are easily controlled with proper applications of systemic insecticides.
Acecaps is one way to treat birches for insect problems.
Cedar Leaf Miner
Although there are a few species of cedar leaf miner in Ontario, Argyresthia thuiella is the most common. The major plant food for this pest is cedar (Thuja).
The adults are tiny (3/8 inch wingspan) white to light gray moths with brown markings on the forewings. The larvae or caterpillars are 1/8 inch in length with a light green (sometimes with a reddish or yellow tinge) body and a shiny black head.
Injury
The larvae mine out the pith of foliar tips starting in the fall and continue during the spring. The mined tips turn at first to a translucent or straw color, later turning brown. The damaged foliage is hollowed out and crumbles easily between your fingers, whereas winter damaged foliage does not. The mines start near the end of a branchlet in the scale-like leaves and extend into other branchlets. Cedar leaf miner damage is denoted by a sharp margin between the healthy green tissue and dead brown tissue. Injury begins in the summer and reaches a climax in the fall. Death of mined branchlets often occurs giving the tree a sickly appearance. The greatest injury probably occurs to hedge rows and ornamental plantings. To find the larvae, gently tear the leaf scale along the margin between the green and brown tissue. Look for a tiny green or yellow larva or pupa in this area in the spring.
Life History
The adults are active from mid to late June. Many tiny glittering moths may call attention to an infestation. After mating, the females deposit eggs on the inner edges of the cedar leaves. The young larvae enter the leaves and mine or excavate between the leaf surfaces. The larvae overwinter in the mines and resume feeding for a short while the following spring. Pupation occurs in late May and the adults emerge soon after.
Management
Under forest conditions, leaf miners are usually kept in check by natural control factors including tiny wasp parasites. On ornamentals there are a few options.
Populations of overwintering larvae may be reduced by shearing the infested tips and then collecting and destroying the tips before June. It may be necessary to spray at times to control an infestation.
Some control can be achieved with a treatment of a systemic insecticide in May.
Control of the adults with an application during peak flights may reduce the amount of eggs laid.
Systemic insecticide should be applied in August to control the larvae when the feeding is just starting.
The insect injury is more pronounced in dry years. Deep watering of the cedars is important.
Fertilizing will also help the damaged plants to recover. Deep root feeding in the fall is recommended.
Dormant Treatment
What is Dormant Spray?
New horticultural oils (a type of mineral oil) are used as a dormant application. This is applied early in the spring before most of the deciduous trees have leafed out.
A large variety of insect pests are controlled by being smothered or suffocated by the oil film. This includes overwintering insects and eggs that hide in the bark of trees & shrubs. By applying the oil, your trees and shrubs can start the year off without any pests. (this doesn’t mean that they won’t fly in later from your neighbours, but it goes along way to reduce the insect populations.) Pests that are controlled include scale, whiteflies, aphids, fruit moths, many mites and the eggs of caterpillars that overwinter on trees.
The added benefit of the dormant spray application is that oil breaks down very quickly and is less toxic to the beneficial insects. Oil applications are very safe to use not only for the applicator but also for homeowners, pets and children.
Dormant Oil is especially important to control scale insects as there are relatively few opportunities to control these pests. Dormant Oil is also recommended for fruit trees, roses and silver maples. It can be applied to almost all trees and shrubs. A few varieties may be susceptible to damage from the oil.
Feeding
Deep Root Feed your Trees & Shrubs This Fall
Do trees/shrubs need to be fertilized?
Healthy plants that are well watered and well fertilized, tolerate insects, diseases and the environment more easily than stressed plants. In fact, healthy trees are less likely to be attacked by insects and disease. A tree or shrub is an investment that takes many years to grow and is difficult if not impossible to replace. Adequate fertility is necessary for both newly planted and established trees or shrubs. Fertilize young trees and shrubs to increase height, width, caliper, and root growth. A mature tree or shrub should be fertilized to maintain its vigour and health. A plant that has not been doing well should be fed to improve its health. Trees/shrubs that have been attacked by insects or diseases should be fed to help them recover from that damage.
When should trees/shrubs be fertilized?
Fall is the best time to feed your trees, evergreens and shrubs. The nutrients that are applied after the plants start dormancy are taken into the roots (which are still active after the leaves fall). The nutrients are held there until the spring. As the weather warms in the spring, the nutrients flow upwards with the sap. This means that they are available to the plant immediately.
Trees and shrubs are best if fed late fall and early spring. An early spring fertilizer application will again be available to the plant at the time when the active growth is still continuing. Of the two applications, however, the fall is the most important and would be the choice if only one application is made.
Micronutrients for Trees
When trees have leaves that are yellowing or leaves with chlorotic veins, the tree may be suffering from a deficiency in a micronutrient. Iron or manganese are a couple of the most common deficiencies. There are a couple of ways to rectify a nutrient lack. For large trees, the best way is to inject the tree with a nutrient that is quickly taken up into the tree. These treatments are not intended to encourage growth but to improve the tree’s health.
Gypsy Moth Caterpillar
What is Gypsy Moth?
An insect pest that can seriously weaken or kill trees. Native to Europe and Asia, it now infests large parts of North America. The gypsy moth caterpillar has been responsible for widespread defoliation and destruction of oak and other broadleaf forests.
Gypsy moth caterpillars prefer oak, birch and poplar. However, when these species are not present, they will attack maples, apple, willow, cherry, spruce and other trees and shrubs.
The first place to reduce the damage from gypsy moth caterpillars is to remove or control the egg masses. Each egg mass can contain from 100 to 1000 eggs. They can be found on tree trunks, branches, on rocks, fences and nearly any other surface including buildings. Scrape the egg masses into a container of soapy water (1 teaspoon of detergent per litre of water) and soak them for one week, or burn them in a woodstove. Another treatment is to spray dormant oil to suffocate the eggs. Remember that no single control method can eliminate the pest completely.
Young gypsy moth caterpillars emerge in late April or early May. They are attracted to light and move upward. As the caterpillar climbs, it spins a silken thread. The caterpillar will hang on to the thread and be blown by the wind until it reaches a suitable host tree.
At this stage, holes are found on leaves, but the damage is minimal.
As the caterpillar continues to grow, changes occure. When it reaches the point where it is about an inch long it will have the 11 pairs of tubercles (spots) on its back. Now they move off the foliage to hide in sheltered places on the tree or ground during the day and do their feeding at night.
By this time in June, the caterpillar can devour almost 7-8 square feet of foliage. Damage is more noticeable and extensive. The caterpillars are larger and can eat more foliage.
Leaves are important to the survival of a tree. Leaves are needed to produce food for the tree. A significant leaf loss will impact the ability of the tree to store food for the winter. Some trees can be almost totally defoliated by the caterpillars. These trees may refoliate in July after the gypsy moth feeding is complete. However, this takes a tremendous amount of energy and food resources from the tree. The tree in effect is borrowing from the food reserves for the coming spring. While a single year of defoliation may not kill the tree, successive defoliations can seriously weaken a tree. This can have serious consequences on trees that are under stress from disease, crowding or other factors.
Ask about our No-spray Acecap Treatments and our organic Insecticide Treatment.
Scale Insects
Scale insects are a very large group of plant feeders that suck the sap from the plant. They spend some time under a waxy covering that protects them from predators as well as many insecticides. Shellac is made from the wax of a scale insect in India.
Euonymus is a hardy, easy to grow broadleaf evergreen that comes in a variety of leaf colours- green, green/white, green/gold. Lately many specimens have been killed by euonymus scale which also attacks pachysandra and bittersweet. Most often you will find the stems and leaves covered with needle thin, white elongated spots. Look closer and you will see larger greyish, oysterhell-looking ones as well. Leaves turn yellow and drop; vines die back. Euonymus on walls are more often infested than other forms.
Eggs begin to hatch in May. The young scales, called crawlers, appear as yellow specks smaller than a pinhead. These small crawlers move to leaves of stems and begin feeding by piercing the plant tissue with thin, thread-like microscopic mouthparts. As they feed, they begin producing the hard protective covering which they extend backwards as they grow.
There can be two generations of euonymus scale. All stages are present in the summer, but crawlers are most abundant in May and August.
Control
Mulch plants and water in dry weather to aid the plant in fighting scale infestation. Trim and remove severely infested material. Repeated Dormant Oil and Systemic insecticide applications are needed to save the euonymus. Treat all parts of the plants thoroughly. The recommended regimen in an early spring Dormant Oil application and 2 applications of insecticide about 10 days apart in May and August (spray when the crawlers have hatched). Unfortunately, euonymus scale is difficult to eradicate.
Magnolia Scale has recently become more prevalent. This is one of the largest scale insects with the females up to 3/8 of an inch across. The body is brown and shiny but often covered with powdery, white wax. When heavy infestations can completely encrust branches, the branches often die. The trees may be severely injured and appear sickly with the leaves remaining small. Excess plant sap is excreted as a sweet, sticky material called honeydew. The honeydew drips on leaves and branches. A black, sooty mold grows on the honeydew blackening the branches and leaves detracting from the plants ornamental value. The honeydew also attracts ants, bees, wasps and flies, which feed on the honeydew and can be anuisance.
Control
Dormant Oil is applied in early spring or November to control the overwintering nymphs. When the crawlers have hatched, they are vulnerable to insecticide treatments. This should be done in late August and again about 10 days later. On larger magnolias, injectable treatments reduce insecticides going on adjoining lawns or non-target plants.  Acecaps are recommended as part of the control program. The insecticide is absorbed into the plant’s sap stream and will kill the target pest.
Pine Needle Scale affects Mugho pine, Austrian Pine. They appear as small white streaks on the needles. Control with Dormant oil insecticide or other insecticides.
Oystershell Scale Infects many plants. The most common are lilac & ash but it also occurs on privet, maple, linden, spirea, viburnum, honeysuckle, fruit trees, boxwood, willow. The scales look like miniature oysters encrusted over limbs, trunks, and twigs.
Other scales can attack junipers, yews, and cedars. Control with acecaps on larger trees. Dormant oil and systemic insecticides should also be applied.
Spruce Disease
Cytospora Canker is the most important disease of Spruce.  It is caused by a fungus and is frequently found on Norway spruce and Colorado blue spruce and its cultivars. It is sometimes found on Douglas fir, hemlocks, larches and balsam fir. It is often associated with weakened trees, trees with injuries, and trees growing in poor conditions. It is seldom found on young, vigorous trees.  Sometimes Cytospora can be confused with mite damage.
Symptoms
Dying of a lower branch with subsequent needle browning is usually the first symptom. The dead needles may remain on the branch or fall off. Higher branches may be affected as the disease progresses. The actual cankers are often seen at the base of branches near the main trunk. Trunk cankers can develop which will result in girdling and death of the tree.
The bark of the cankered areas is not visibly different in color nor does it become sunken. Resin flow is usually associated with Cytospora canker and the white patches are quite conspicuous on the bark. Resin flow can, however be associated with any injury to branch tissue.
Control
There are a number of things that can be done to reduce cytospora canker.
Maintain tree health. The two most important steps are to water and fertilize on a regular schedule.
An amount equal to 2 inches of rainfall is needed every 2 or 3 weeks in one complete heavy soaking to the feeder root area. Turn the hose to a drip and let the water soak in slowly.
Feed the plants regularly. Fall feeding in late October to mid November is the best time. Deep root feeding is an excellent way. Spring or early summer feeding is also good. Granular or water soluble fertilizer can be used.
Control insects and mites: especially spruce gall adelgids and spider mites.
Avoid any disturbance to the root system that will result in injury or poor root growth. Avoid bark and stem injuries.
Selectively prune out branches that retard air movement near the base of the tree. These low branches are often wounded by lawnmowers, pets, and general traffic. Weak and injured branches should be removed flush with the tree trunk. Pruning during wet periods can spread the disease; therefore prune only when foliage and trunk are dry. Pruning tools should be disinfected with 70% alcohol or mixture of 1 part bleach and 9 parts water.
No chemical control measures are available. Some reports indicate a Bordeaux mixture or other fungicides containing copper, sprayed after removal diseased branches may help retard disease spread. Early spring or late fall applications may prevent further spread.
Vertically mulch to relieve compaction, poor aeration, and inadequate water penetration.
Top Problems
Here are the top Tree & Shrubs Insects and Diseases problems. (Actually it’s eleven, but that’s pretty close to 10) Remember to keep your trees & shrubs well-watered in dry weather. Good nutrition is also important. A healthy tree is better able to resist insects and diseases. We recommend deep root feeding in the fall to make sure that nutrients are available to the plants when needed.
1.    Euonymus & Magnolia Scale – See Scale Insect Factsheet
2.    White Birch Trees – The Birch Leafminer and Bronze Birch Borers. See Birch Care Factsheet
3.    Honeylocust Leaf hopper — Locusts such as Shademaster and Sunburst can be attacked by Leafhoppers. These are small green wedge shaped bugs. They suck the sap from the leaves, often discolouring and disfiguring the leaves and stunting growth. They can also transmit virus diseases. Control with foliar sprays or Acecaps.
4.    Gypsy Moth Caterpillar – these caterpillars are dark and hairy with a double row of 5 pairs of blue and 6 pairs of red spots from head to tail. They feed on many tree species. Favourites include birches, lindens, crabapples, mountain ash, willows, oaks, blue spruce and many other trees. Voracious feeders, these caterpillars have been known to defoliate trees. Remove egg masses. Trap caterpillars by tying a band of burlap around tree trunks. Inspect daily and destroy caterpillars. Use Acecaps to prevent damage or foliar treatments.
5.    Cedar Leaf Miner – Cedars with Leaf Miner have the tips of the leaves brown. During June and July tiny grey moths take flight when the branches are disturbed. Damage is usually worse on the lower branches. If possible trim before June, then destroy the clippings before the adults emerge. Treat with systemic insecticide in May and/or August.
6.    Diseases Problems -In general, rake and remove leaves and fruit each fall to reduce sources of disease. Flowering Crabs are susceptible to powdery mildew, scab and black spot fungus diseases. Prune to increase air movement. Treat with a fungicide in late May-early June. Insecticides should be applied at the same time. Hawthorns suffer from leaf spot and rust disease. Treat hawthorns with fungicide just after flower petals fall. Catalpas, lilacs, honeysuckles and maples are attacked by powdery mildew. Proper timing is difficult with powdery mildew, but treatments usually reduce the severity of the disease.
7.    Viburnum/Snowball Insects- Aphids suck the sap from leaves and disfigure them. Viburnum leaf beetle (larvae and adults) will skeletonize leaves. Use foliar sprays to control. Usually more than one treatment is necessary.
8.    Spruce Gall Aphids — Actually an adelgid (close relative of the aphid). The pest can cause the spruce to form galls near the growing tips. The galls result in slowed growth, sparse branches and distorted growth. Removing galls when they are still green (before mid-July) will help slightly. Treat with foliar spray in late-September and October. Spring treatments are less effective as timing is more weather dependent.
9.    Fruit Trees – Rake and remove infected leaves and fruit each fall. We recommend starting with a dormant oil treatment. Orchards treat fruit every week but in home orchards we recommend about 2-3 foliar applications of insecticide/fungicide.
10.    Pines – Austrian and Mugho Pines are often attacked by sawfly larvae. These interesting caterpillars will move in unison. They can quickly defoliate branches but are relatively easy to control with an insecticide application. Pines occasionally get scale insects as well (see Scale Insect Factsheet)
11.    Tent Caterpillars – The Easter tent caterpillar form tents in the crotches of limbs of apple, crab, cherry, and other deciduous trees and shrubs in the spring. Fall webworms spin large webs over the branch tips in August and September. Prune out and destroy the tents if possible. Insecticides can be effective is the tents are thoroughly soaked.
12.    Many other insects and diseases can affect your trees and shrubs. Please call for a consultation.

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