Knowledgebase
What is causing these bark holes on our Locust tree? #386341
Asked February 23, 2017, 7:33 PM EST
Thanks
Barb
Arapahoe County Colorado
Expert Response
While your honeylocust tree may have some insect injury, the photos you provided suggest that branches are infected by Nectria canker, a fungal disease.
Nectria canker generally affects only stressed or declining honeylocusts....for example, those that have not received enough water, those that are planted where root spread is very limited, or those that are declining due to age. Weather conditions that weaken the tree may have favored canker development...for example, the 'Polar Vortex' freeze of Nov 11, 2014, when temperatures dropped 65 degrees.
You may have noticed that some branches died back last year or in previous years. They may have failed to leaf out, or had premature leaf color and premature leaf drop.
Hopefully the canker disease has not affected the main trunk. Cankered areas may ooze some amber-colored gum or sap.
You'll want to have any dead wood or dead leafless branches removed (pruned out) this spring during dry weather.
Try to increase the vigor of this honeylocust by watering its rooting area sufficiently and by watering during dry warm snowless periods in winter. If it is growing in or near a fertilized lawn, it should be getting enough fertility.
Avoid any wounding of the trunk with lawnmower or string trimmers.
More details: http://extension.colostate.edu/topic-areas/yard-garden/honeylocust-diseases-2-939/
Barb Schroeder
Barb,
oozing sap would indicate a stressed tree OR an insect "borer" under the bark. I did not see the oozing sap that you described. Yes, a tree can recover even if you see some sap ooze on the trunk.
It looks to me like your honeylocust tree has had some injuries and stresses over its tenure in your yard. The exposed wood looks like it has been stained by fermentation products of bacterial wetwood a few years ago. Bacterial wetwood is a chronic disease of elms, cottonwoods and honeylocusts. It can contribute to a general decline, especially on trees of low vigor.
Suggest you have deadwood removed (pruned out). Fertilize the tree's rooting area lightly in May. Lawn fertilization can take care of this for you.
Keep the tree watered during growing season and dry spells in winter.