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Over the Garden Fence

Where gardeners come to find out what's happening out in the yard.

Controlling Fruit Tree Diseases

Posted by Richard Hentschel -

Home orchardists struggle from spring through the summer to make timely cover sprays, hoping to harvest good quality fruit. Several practices can help you grow fruits that are the envy of the neighborhood.

Apples may be the hardest of the tree fruits to manage, as there are a couple of diseases that really affect how your crop turns out. Apple Scab and Cedar Apple Rust (CAR) are the typical culprits. If we see we have a problem with either one by mid-summer, we have waited too long to start those cover sprays. Both diseases establish themselves during our early cool, wet weather, but they differ in how each disease influences foliage or fruit.

CAR finds its way to home orchards by overwintering on cedar and juniper evergreen trees in the neighborhood and the spores are dispersed by the wind, infecting very young foliage and developing apple fruits. Apple Scab never leaves the home orchard or yard, and instead overwinters on fallen leaf litter, just waiting until the following spring. When the weather is just right, those overwintering spores emerge from the leaf litter and get carried along in the wind.

Several management tools can reduce or slow the initial infections. If not addressed, these diseases will lead to a loss of foliage and/or damaged apples. In either situation, it is the foliage that makes the food that produces the apple. If the food factory cannot operate properly, then the apples are of smaller size and lesser quality.

If you are just planning a home orchard, whether or not it is just for apples, variety and cultivar selection is critical. Planting disease resistant fruit trees means a greater chance of getting a good quality fruit. Read the catalogs carefully before ordering. If you are not sure the variety you are interested in has good disease resistance, contact the grower or research the fruit tree on the internet. In general, it is up to the grower to do the homework to be sure. If you have an orchard in place, anytime a fruit tree is replaced, consider disease resistance then too.

Canopy structure is another management tool that benefits lessoning the disease outbreak. By proper scaffold selection on your fruit trees, along with your annual pruning, you create an environment that does not favor disease development. That open canopy allows sunlight and air to enter, warming and drying out the foliage and early developing fruits. The fungal spores that cause disease cannot survive long enough in that environment to become established in your fruit trees. We can always hope for a dry, warm spring, but we need to plan for a cool, wet spring every year and be prepared to make treatments.

Apple is an easy example of why we need to manage our trees well, yet the principles are the same for any fruit tree when it comes to disease management. Starting with those early sprays each spring will give us the disease-free fruits to brag about with family and friends.



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