Canker in Fruit Tree

Hello Lynn

I have a little mini orchard on 25% of my allotment, I have been on this plot 6 years and I had brought from my first plot a family apple tree and it is not very prolific with the fruit though only a few apples on this year where most tree's don't have a thing. It has quite a lot of canker all over it and someone mentioned that it was air-borne and could affect the other trees nearby; plum, pear, and another apple.

I am going to cut it down and replace with a smaller tree can I go ahead now to dig roots out and dig up another smaller tree and put it almost in the same place?




Dear Willie

On the face of it, this would appear a reasonable idea but there is a disorder known as Specific Apple Replant Disease (SARD) which particularly affects fruit trees (including apples, plums, pears and cherries) along with roses and other shrubs.

The exact cause is unknown but is believed to be caused in some part by the build up of soil borne diseases, pests and pathogens over the long life of the previous tree or shrub. It may be that your replacement apple tree is completely unaffected but when the disease is present, growth of the new tree or shrub is generally poor and the plant may even die.

There are two ways we can look at your situation; either take some remedial action and plant the new tree on the site of the old one or try to improve the health of the existing tree which is afflicted by canker. Let’s take a look at treating the canker first.

It’s partly true to say that the fungal spores of apple canker are airborne (during the winter and spring) and are also dispersed by water and rainfall in the summer. All fungal diseases need an entry point to infect new trees so pruning at the correct time of year and using a pruning compound or wound sealant will help prevent infection. Good tree husbandry also plays a major role in preventing canker; check the tree for symptoms regularly, spray for woolly aphid when present and be sure to prune out any dead, damaged or diseased wood promptly. All cankerous prunings should be incinerated.

There are also a couple of fungicide treatments you can use in the shape of Bordeaux Mixture and the well known Bayer Fruit and Vegetable Disease Control and these can both be used very soon. Apply either of them to the tree as a spray after picking and again when around half the leaves have fallen; this protects the leaf scars from infection.           

However, if you would like to take a chance on replacing the tree then there are a few techniques you can try to help lessen the effects of SARD.

  • Remove the existing soil and replace with fresh from another area of the garden where trees and shrubs have not been planted. Make sure the area of soil removed covers the likely root spread (or as much as is possible) of the new tree
  • Follow good tree planting practice by adding bonemeal and well rotted compost or leaf mould to the planting hole and back filling with a mix of fresh soil and organic matter
  • Feed the new tree with a nitrogen rich fertiliser in early spring to encourage vigorous growth
  • Try adding our Root Boost mycorrhizal fungi granules to the planting hole, ensuring the granules come into contact with the roots of the tree
  • Water, feed and mulch the tree in spring
  • Plant any bare root tree in November when the tree is dormant but the soil is not frozen or waterlogged and is still warm from the summer before the winter frosts set in     

I hope the above information gives you plenty to think about and also helps you decide which course of action to take. If there’s anything else you’d like to know then please don’t hesitate to contact me and the best of luck with your mini orchard.

Kind Regards

Lynn Burton
Horticultural Adviser