I have a young walnut tree which is in its 3rd year that was planted by a squirrel in a plant pot in my garden. It has been in a large terracotta pot and has grown well each year and has been healthy. The tree has started to leaf again over the past 4 weeks with no problems until I noticed this morning there is some dark brown liquid seeping from a couple of different areas on the main trunk of the tree. Can you please advise. . .
Walnut Tree Disease
Certified GKH Gardening Expert
Based on my research, I believe that your tree has a bacterium named 'Brenneria nigrifluens' which causes shallow bark canker in walnut trees. It would cause the dark brown liquid exuding from the main trunk of your tree. Since this canker does not significantly harm walnut trees there are no published control measures.