Oystershell scale is affecting many cotoneaster hedges throughout the city of Calgary. We have also seen this insect pest affect; apples, mountain ash and hawthorn trees. In most cases if an infested hedge looks like it’s dead or dying, rejuvenation and post application of oil and monitoring are required. Prior to application carefully examine your tree or shrub to identify the target pest or problem. Most spray insecticides are non-selective and will also kill beneficial insects. Dormant oil must be applied early in the spring prior to leaf out. The reason applications must be made while trees and shrubs are dormant is that the product will cause damage to the leaves. Never spray on evergreens as this will cause permanent damage and sometimes discoloration of blue species.
A few exceptions are Pure Spray Green because the product label states that application is safe on leafed out plants, the next exception would be on a cotoneaster hedge that has been freshly rejuvenated. When applying make sure that you coat every portion of the plant until the product begins dripping off of the plant being treated. This assures that you get all of the insect shells covered with the insecticide. Make sure to read and follow the product label and wear appropriate personal protective equipment.
You will need
1 Hose, you probably already have one if not get a professional non kink hose they’re worth every penny
2 Dial calibrated hose end sprayer +/- $20
3 Horticultural oil or Dormant oil or Pure Spray Green +/-$20
1 Read labels
2 Wear personal protective equipment (plastic dish gloves, eye protection, hat, clothes to cover your skin)
3 Set the dial to 20 on the hose end sprayer and fill it with the oil
4 Thouroughly spray the plant until every portion is covered
5 Continue monitoring pest activity and reapply if required when plants return to a dormant state
People often ask how to water a tree, when and how much. Is there a regular schedule that one should follow to water trees and most plants in general? The answer is simple, check the soil regularly and water when dry. Do not overwater as this prevents the roots from having access to oxygen, low oxygen levels to the roots will encourage them to rot. Trees take up water through the roots by osmosis and transpirational pull which means water evaporating from the leaves is pulled up from the roots. Trees transpire throughout the day and mostly respire during the night, this is important to know when deciding what time of day to water.
The best time to water is during the morning so that the tree can have access to water when it needs it. Avoid watering during the hottest period of the day as much of your water will be wasted by evaporation from the ground. How much to water is also an important factor, ideally the best way to water your trees is to apply a large volume of water over a long time period, water heavily and less frequently.
A soaker hose is perfect for watering trees because it allows for water to be applied slowly so that the soil can be watered to its full capacity instead of just watering the surface with a sprinkler. Where you water should also be considered because you want the water to be where the feeder roots are. Let’s consider roots for a moment, roots can grow out as far as a tree is tall so you need to water where the fine roots are.
Think of a tree like a petroleum industry, fine roots far from the refinery tap water wells, think of the larger roots closer to the trunk as pipelines to transport the water from the wells all the way up the trunk to the leaves which act as refineries. When you water close to the trunk think of it as pouring oil over a pipeline instead of having it flow through the pipeline. Moisture on the trunk can also cause damage and rotting on the bark of trees growing in a dry climate like our own. You can also follow the dripline example for watering most trees, water at and past the dripline to make the most of your watering efforts.
One exception for watering at the dripline would be columnar trees, I would water these trees wherever they cast shade (the shadeline) as this is where the roots would most likely be found considering the trees height. If a mature columnar tree had all of its roots only within the dripline it would surely fall over. Mature trees need significantly more water than young trees. Remember leaves pull water, more leaves/refineries means that more water is required for the system to work at capacity.
What about watering dormant trees and evergreens during the dormant period of the year should we? Yes if soil conditions are dry then the soil should be kept moist to keep the roots healthy and make water available for when the tree needs it. Watering during dormancy also helps keep a healthy root environment by creating beneficial conditions for microbial activity that promotes healthy soil and root development.
Most importantly is that you water your trees because it’s probably the most important resource that you have at your disposal to keep a healthy tree.
Calgary has had a widespread epidemic of black knot for well over fifteen years and the problem is only getting worse. Apiosporina morbosa is the Latin name for this fungal pathogen which predominately spreads during cool moist weather conditions in the spring. Control of the disease in infected trees is best done by pruning out symptomatic branches that appear as if they have a burned marshmallow on them. Black knot does infect trees systemically which means that even if infected branches are pruned the disease will continue to proliferate within the tree until it is dead and removed.
Because of the natural riparian areas within the city of Calgary it is nearly impossible to completely control the disease as it spreads on native plant species most commonly the western chokecherry Prunus virginiana. The best way to cure tree diseases including black knot in Schubert chokecherry and mayday species is to plant disease resistant trees, in other words the answer is simple do not plant mayday or chokecheery trees because they are guaranteed to get black knot. If you have a tree with a severe infection consider removing and replacing the tree rather than delaying the inevitable. Trees that only have a handful of knots appear per year can be pruned and preserved until the infection worsens.
Keeping a tree healthy will also ensure better chances of success, water regularly when dry, improve soil and site conditions if possible, prune symptomatic and dead branches, avoid over fertilisation and high nitrogen fertilizers.
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