Apple trees and especially certain species of crab-apple trees are susceptible to apple scab. Apple scab is caused by a fungus you can recognize by dark grey, brown, or black spots (scabs) on the leaves and fruit.  It is not recommended to treat infected trees with synthetic pesticides.  Apple scab does not threaten the survival of the tree, but it can cause it to lose leaves all summer.  Abnormally cool, damp weather in spring can be responsible for the development of this disease.

What can you do to prevent this problem from returning next year?

 For new plantings: select cultivars resistant to this type of disease and above all do not plant vulnerable species that are not well-adapted to the environment where you want to plant them.  This is called the concept of “the right plant in the right place”.

 For established trees: it is imperative to collect the diseased fallen leaves and dispose of them so the fungus cannot winter in the soil and re-contaminate the tree again the following year.

 In spring: it is imperative to treat your fruit trees with a dormancy oil.  This treatment eliminates the eggs and spores of different pests and helps to reduce the potential populations of pests and diseases.  Water deeply and work your soil well with compost or manure.  Your trees will be more resistant to insects and potential diseases.  You can also smaller trees with an application of bicarbonate of soda (Cow Brand) or Horsetail tea (Equisitum arvense).

Horsetail tea:  Boil 60 g of dried Horsetail in 4 litres of water.  Once cold, dilute with 4 times the volume of water.  Spray on the foliage.

Bicarbonate of soda:  Combine 1 tablespoon of baking soda + 1 teaspoon of liquid soap or vegetable oil.  Add to 4 litres of water and mix well before each use.