A Fruit Tree With a Sap Problem

Written by tracy hodge
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A Fruit Tree With a Sap Problem
Cytospora canker causes gummosis in peach trees. (Photos.com/Photos.com/Getty Images)

Fruit trees are grown for their shade and the fruit they provide. However, some fruit trees develop a condition known as gummosis that causes sap to ooze from the tree. A fungus causes this condition affecting peach, cherry, apricot and plum trees. Gummosis causes defoliation of fruit trees. A severe infection kills fruit trees.


Gummosis causes sap to ooze from cankers on fruit trees. This condition is caused by Cytospora fungi or Botryosphaeria fungi, which overwinter in dead wood and infected bark. Infected wood releases fungal spores that are carried on the wind or splashing water to infect fruit trees in close proximity. After fungal spores land on trees, they enter through wounds on the bark. Winter injury, pruning injuries and insect boring are the most common entry points. Gummosis symptoms are most severe when temperatures range from 21.1 to 29.4 degrees C. Spring rains help this fungi seep into fruit tree bark.


Gummosis begins with small areas of oozing sap. As the fungi destroy tissue underneath the bark, sunken cankers develop. As the disease spreads, the lesions run together and often cause the entire trunk to ooze sap. Cankers enlarge and girdle the branches and fruit trees may become completely defoliated as time passes. Gummosis can kill fruit trees if the trunk is infected, according to the Missouri Botanical Garden.

Cultural Control

Avoid wounding fruit trees during pruning or with lawnmowers, as this is where fungi enter trees. Keeping your fruit trees healthy and stress free also helps prevent infection. Since boring insects injure tree bark, take steps to prevent your fruit trees from attack. Pruning and destroying diseased branches keeps fungi from overwintering in dead wood.


No chemical-control products treat gummosis once it infects fruit trees. Using chemical controls to keep insects from damaging your fruit trees may prevent infection. Unhealthy fruit trees and fruit trees with reduced vigour are at risk of developing this disease. Avoid pruning in the summer months, as this is when fungi colonises rapidly. Planting fruit tree varieties resistant to gummosis also prevents infection.

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