Plant Pathology Infobytes

June 20, 1996
Get Tough On Bad Apples

Home orchardists who've done a good job controlling apple diseases on fruit could be tempted to abandon a spray program at this point in the season. Stopping too quickly isn't a good idea, since now is a critical time for controlling bitter rot, the number one disease of apples in Mississippi.

Although the fungus which causes bitter rot is active earlier in the year, this disease doesn't really take off until fruit are about half mature. During periods of rainy weather, fruit infection occurs, and by the time fruit begin to mature, bitter rot is often in an advanced stage on many fruit over the tree.

Fruit infection shows up as slightly sunken, circular brown spots that are surrounded by a reddish halo. When the spot increases to about an inch in diameter, spore-bearing structures appear in concentric circles on the surface of the spot. A brown decay beneath the diseased spot extends toward the fruit core in th shape of a cone. Within a short time, infected fruit rot completely and fall from the tree.

To protect fruit from bitter rot infection, continue fungicide spray applications with captan fungicide. Several applications of captan, seven to ten days apart, will be needed in order to fully protect fruit from infection until maturity is reached. Other fungicides, such as Bordeaux Mixture, are also approved for apple bitter rot control and should be available at garden and farm supply stores. Read and follow all application directions presenton the fungicide label.


Written by the late Dr. Frank Killebrew

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