This text is part of the special Pleasures notebook
You notice that your tree is not doing well and you wonder what is the cause of this problem? Be aware that it is not easy to make a diagnosis, because the causes can be multiple: nutrient deficiencies, stress, climate, animals, the presence of an insect or damage caused by it, root problem or disease. To try to find your way around better, we present here some diseases that affect our beloved trees.
Diseases that quickly cause our beautiful green giants to wither can be caused by microscopic fungi, viruses and bacteria. These pathogens, sometimes present in the soil or carried by wind, rain, water or insects, infect and sicken your trees, sometimes causing premature death. Here are some diseases encountered during consultations.
My thing
Observe your plants regularly, from top to bottom. Walk around your land and carefully look at the trees and plants there in order to quickly detect any health problems. If you suspect something, do not hesitate to consult an expert.
Powdery mildew
Do you see a tree or any other plant that has a white, powdery growth on its leaves? This is powdery mildew. A fungicide sprayed on the leaves can help cure it.
Phyllosticta
Have you noticed elliptical-shaped freckles oriented in the same direction as the veins on the leaves of your trees? These are caused by a fungus with a very serious name: Phyllosticta. It is advisable to prepare a Bordeaux mixture (a fungicide composed of copper sulfate and slaked lime available in garden centers) that you will spray as a preventive treatment to avoid worsening.
Anthracnose
Large beige or brown spots with a black outline affect the leaves of your tree and they dry out and fall prematurely to the ground? This is anthracnose, a disease caused by fungi and which is mainly observed on maples, birches, oaks and ash trees. Affected trees do not die, but remain weakened. What can be done to combat this disease? Simply collect the leaves that have fallen to the ground in the fall and get rid of them, eliminate branches with cankers, and prune the entire tree to improve air circulation. Collect and destroy the fallen leaves, where the fungus may spend the winter.
Fire blight
Fire blight is caused by bacteria and mainly attacks plants in the Rosaceae family (apple trees, pear trees, Saskatoon berries, crabapple trees, plum trees, rose bushes, etc.). This disease is the most virulent and contagious of all. It can destroy everything in its path: the leaves wilt, become dark as if they were burned and end up curling up on themselves, the fruits and flowers die (but do not fall). To save your tree, cut off the affected parts as soon as possible. After each cut, it is imperative to disinfect your pruning tools.
Sooty mold
Sooty mold, or black sooty mold, has the particularity of developing mainly on sugary excretions of aphids. This fungus then causes a “black sooty mold” to appear on the leaves of affected plants. This is a mold that grows rapidly with the moisture it absorbs and which prevents the normal growth of the leaves. This disease only affects the plant very slightly, but can reduce (a lot) photosynthesis. If there are no aphids, there is little risk that the disease will develop. So make sure to eradicate them to avoid this condition.
Rhythm
What? Tar on my tree? Tar spot does not go unnoticed when it appears on the upper surface of the leaves. Caused by fungi of the genus Rhytisma, it is observed on all species of maple. Fortunately, this disease does not affect the quality of the maple sap produced. Collecting dead leaves and destroying them throughout the summer and fall will reduce the quantity of fungi present on the ground, but will not completely prevent the risk of infection by neighboring trees.
More resilient trees
A healthy tree will be better able to resist the presence of pathogens and defend itself against them. This is not the case for stressed trees, those deficient in nutrients or those located in polluted environments. To put all the chances on your side and have a healthy tree, think about:
• check health status when purchasing;
• choose disease and insect resistant varieties where available;
• respect planting distances;
• do not overwater and monitor excess humidity;
• promote aeration of plantations by sowing and planting less densely, but also by carrying out regular weeding.
What is afflicting the thuja, this king of hedges?
Thuja is a sturdy conifer often planted in hedges for its robustness and rapid growth. Various diseases can affect it, one of which is caused by Phytophthora cinnamomia fungus that attacks its roots (rot) and causes it to die back. The symptoms are rot spots that appear on the roots and the collar. There will also be a sudden and progressive browning of the foliage, then of the entire plant if nothing is done. To overcome the problem, eliminate the affected and doomed thujas. For the others, spray the base of the trees, in spring and autumn, with a copper-based solution, such as Bordeaux mixture.
As for Didymascella thujinathis is a fungus responsible for needle blight on cedars. Symptoms first appear on a few scales, then spread rapidly to form large brown spots on the branches, causing the affected needles to partially fall off. The disease can be fatal for young trees. Remove affected branches as soon as possible and stop pruning. As a preventative measure, regularly spray a foliar fertilizer rich in magnesium. Fertilizers adapted to the nutritional needs of cedars are available on the market.
Don’t make the mistake of getting your chainsaw out too quickly! Know that even if a tree is sick, or even very sick, and loses all its leaves for example, it can recover or still be strong enough to remain standing for a very long time.
This content was produced by the Special Publications Team of Dutyrelevant to marketing. The writing of the Duty did not take part in it.