Dealing with Apple Scab

This week’s guest blogger is David King from the Learning Garden. He’s a great friend and an amazing gardener who does more for the Los Angeles gardening scene than I have space to write.  He is currently writing a book on growing food in Southern California, and today he shares his helpful tips for managing apple scab. Take it away David!

For many of us wanting to grow more food on our own, fruits and nuts from trees comprise a major part of our food plans.  Fruit-bearing trees produce so much more food for so little effort that, once they are established, many of us consider them a “no-brainer.” 

They are not without effort, however.  They do require some pruning and get diseases that require attention on such diseases is called Apple Scab.  This is a fungus infection (Venturia inaequalis) in apples. Affected apples get an ugly spot that makes the apple look unpalatable, however, the blemish, like beauty, is only skin deep.  Still, the first time on sees apple scab on apples, the first thought is definitely not, “Yummy!”. 

Apples with apple scab

Like all fungi, apple scab thrives in moist conditions, a condition hard to avoid if you live within easy access of the ocean.   Some varieties are more prone to it than others and I have the dubious fortune of owning several: Anna and Dorsett Golden.  There are not many varieties of apples that will do well in a climate with so few cold hours, so learning what to do about it has got to be a priority.

The disease infests the leaves as well as the fruit – these leaves fall to the ground where the fungal spores wait to re-infest next year’s leaves and fruits.  The key is to interrupt this cycle.

What to Do?

After the current year’s harvest is over, comb the tree looking for leaves that show signs of lesions.  Get them off the tree.  Try to get all of them – those you do not get are going to fall to the ground where they will infest next year’s crop.  The plan is to stop the process of re-infestation. 

With the infested fruit and leaves removed from the tree, spread a cardboard layer out from the base of the tree out to the edge of the drip line.  Cover the cardboard with wood chips as deep as you can, up to a foot deep.  This will decompose over time – the idea is to entomb the spores lying on the ground under this mulch to prevent the spores from being splashed up into the fruit and branches of next year’s crop.  When doing the annual pruning, take care to remove all the cut wood from this area as it too may contain fungal spores.

What to Expect

This process will not eliminate the disease.  It will, however, cut down on fruit losses from the disease and will enable a more respectable harvest.  Plan to repeat this procedure on down the line.  The organic remedies to apple scab include copper, Bordeaux or soluble sulfur mixtures that provide no more control than the method above and most of those proposed solutions will contribute to the death of beneficial insects and bacteria—not a bonus.  The best control comes from planting resistant varieties if you live in an area with more cold weather than coastal Southern California.  Better to eat apples with apple scab than to attack your environment with poisons.

 
Apples with scab are perfectly fine on the inside, and still good to eat.

The apple interior is not affected, so look for recipes that will use your apples peeled and cooked.  Apple pie, apple cobbler, applesauce, apple juice and a host of other apple products can become a part of your strategy to deal with apple scab.

For more information about The Learning Garden and all that David is doing, take the Learning Garden’s Virtual Tour. 

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