Apple Black Rot

 


Black rot is a disease of apples that infects fruit, leaves and bark caused by the fungus Botryosphaeria obtusa. It can also jump to healthy tissue on pear or quince trees, but is typically a secondary fungus of weak or dead tissues in other plants. Begin checking your apple trees for signs of infection about a week after the petals fall from your apple blossoms. 

Early symptoms are often limited to leaf symptoms such as purple spots on upper leaf surfaces. As these spots age, the margins remain purple, but the centers dry out and turn yellow to brown. Over time, the spots expand and heavily infected leaves drop from the tree. Infected branches or limbs will show characteristic red-brown sunken areas that expand each year. 

Fruit infection is the most destructive form of this pathogen and begins with infected flowers, before fruits expand. When fruits are tiny and green, you’ll notice red flecks or purplish pimples that enlarge as the fruit does. Mature fruit lesions take on a bulls-eye appearance, with bands of brown and black areas expanding outward from a central point in each lesion. Commonly, black rot disease causes blossom end rot or mummification of the fruits on the tree.





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