Management efforts for tree diseases rely on prevention strategies. It is easier to determine the disease of a tree than it is to treat it therefore methods to prevent infection in the first place or spreading are key. Diseases that invade a trees vascular system can interfere with water and nutrient transportation and quickly kill them. Pests and diseases are treated in very different and complex ways.
Monitoring your tree
The best defence against diseases which invade the vascular system is to monitor the health of a tree in terms of fertilizer, weather, soil, available light, temperature and watering conditions. Regular maintenance such as fertilising and watering a tree can give it a whole new lease of life preventing it from catching infections of disease. Symptoms which appear to be caused by pathogens are caused by abiotic factors which are non-living such as air pollution, insects and nutrient deficiency.
Another option is the use of fungicides which control specific diseases by hindering the growth of fungi. An issue with this is that a fungicide should be used as a prevention method rather than as a direct solution. Fungicides should be applied to plants and trees before infection occurs in order to stop the damage that fungi causes. Fungicides work in 3 ways: to control a disease during a plants growth, to increase the productivity of a plant and to improve the storage life and quality of a plant.
As a plant protector, the pesticide should only be used when it has been determined that a tree has a symptom that fungicide can control. Vascular diseases such as Verticillium wilt are caused by different organisms which cannot be controlled by fungicide, herbicides or insecticides.
Integrated Plant Management (IPM)
Integrated plant management (IPM) systems monitor trees and pathogens in order to control the impact of diseases on plants. Cultural, biological and chemical control measures suppress pest populations before they go above the economic injury level (EIL).
Common treatment for control of diseases:
Do not overhead water, plant in well-drained soil, allow space surrounding the tree for air circulation, rake up leaves and remove dead branches.
Do not overfeed or over prune the tree, cut outside the infected area and get rid of the branches.
Try not to wound the tree or flood it with water, remove infected areas in dry weather and clean the tools in-between doing so.
Downey Mildew Disease
Try to avoid irrigation in the spring, get rid of any fallen leaves in the autumn.
Try to attract birds and other organisms to the tree (unless they seem to be causing the problem), don’t spray the galls just prune them out when they occur to be the key problem.
Ensure that the tree has good air circulation, try to protect it in the winter from cold frosts, remove tips of the tree which are damaged, remove fallen needles.
Powdery Mildew Disease
Provide a good amount of air circulation and soil drainage, spray the tree with a garlic spray and remove any symptoms of disease.
Sooty Mold Disease
Use a mild soap spray to control aphids.
Ensure that the tree is well watered and composted, do not plant more trees around an infected one, remove infected branches and feed the tree with a nitrogen fertiliser such as bonemeal.
Fire Blight Disease
Unlike wilt disease, do not use a nitrogen fertiliser, instead, remove any infected areas and disinfect tools in between doing so.
Leaf Spot Disease
Do not overhead water, use a hose to water the tree, ensure there is adequate space surrounding the tree, use mulches (material placed on the surface of soil) under the tree and remove spotted leaves and branches which have fallen.
Leaf Blister Disease
Maintain plant vigour (its capacity for strong, healthy growth) and remove fallen leaves and branches.
Do not position other trees which are susceptible to a rust disease near each other, ensure the tree has plenty of water, increase soil matter and remove galls on evergreen and any fallen branches.
Tree sprays and natural horticultural oils can be one of the most effective and cost efficient ways of treating and fighting infectious diseases. However, fungicide spray treatments and prevention methods such as IPM can often fail if disease attacks uncontrollably. Arborists should be contacted when the spread of disease has become uncontainable and where prevention methods have failed.