Have you noticed any gum oozing from cherry tree branches and trunks? It's called gummosis, a sign that your cherry tree is under some sort of stress. That's right, trees can get stressed! Gummosis is not a disease but can be associated with disease or insect damage to the tree. Gummosis is most common on stone fruit trees such as plums, peaches, nectarines, and cherries.
Gummosis is often associated with cankers, which are sunken lesions on trunks, branches, or twigs. Cankers may be caused by mechanical injuries (such as lawnmowers or pruning), insects, winter damage, sunscald, herbicide injury, and various fungal or bacterial infections. In response to these stresses or injuries, a sticky amber ooze or gum is exuded from these lesions (see pictures). With time, cankers may become more obvious, as branches swell or form corky growths on the margins. Severe damage or infections may cause wilting of leaves and eventual death of fruit-bearing wood.
Insects such as peach tree borers feed under the bark, creating wounds and tunnels on the inner bark. As a result, branches exude gum through wounds. Fungal pathogens from the genus Botryosphaeria may also infect cherry trees and cause cankers between the trunk and scaffold limbs. These fungi are usually opportunistic and colonize plants when their defenses are low. On the other hand, bacterial cankers caused by Pseudomonas syringae can sometimes become a serious disease in commercial orchards. Bacteria colonize leaf surfaces and enter the tree via wounds, creating oozing cankers and girdled limbs. Sometimes entire limbs may wilt and leaves and fruit may show spots.
In summary, cherry gummosis is the plant's reaction to stress. Pathogens or insects may be involved, but the best way to prevent gummosis is by taking an integrated management approach. Avoid unnecessary mechanical injuries to your tree and prune under dry weather conditions. Provide a good growing site (well-drained soils) for your tree and a balanced fertilization program to promote vigorous growth. Also, practice good sanitation by pruning and destroying cankered limbs.
Gummosis is a sticky amber ooze or "gum" exuded from lesions on stone fruit tree bark.
Gummosis may be caused by cankers, mechanical injuries, winter damage, sunscald, insects, or pathogens.