Question

Pistachio Stress   QUESTION: We are having a problem with one of two Chinese Pistachio trees in our front yard (south side of house) located in Rockwall Texas.  The tree was originally planted in June, 2005 from a 65 gallon container.  Currently, the southern-most main limb of the tree is showing some openings in the bark and some sap running down this main limb near the trunk of the tree.  The foliage on this limb is showing traces of browning and yellowing.  Some of the lower limbs on this tree were pruned in March of this year.  Assume this could be a result of the harsh winter of 2010-2011 and the very hot summer of 2011 thus far, but we wanted to get your expert opinion on the possible causes of the problems being encountered by this tree.  
 
I have attached one photo showing the bark and the sap...additional photos are available if desired.

Thank you for kind assistance

ANSWER: Hi Nancy:

I am unable to see much detail in your photo, but does the sap flow seem to originate at the junction point of one of the major branches in the fork? If so, this area may "pulled apart", leaving an opening where sap is oozing out of this bad connection point between the side branch and the main trunk. The branch junction, for one reason or another, may have become weakened. If so, the limb may eventually split downward, leaving a large open wound. Sounds as if this may be occurring since the leaves are browning.  Several reasons can account for the separation.  Sometimes a wind storm can cause branch movement enough to weaken this connection or just the sheer weight of the branch can do this. Internal disease decay or insect activity in this area is also a possibility.  Some trees like the ornamental pear (Callery pear)develop weak branches as the tree gets more size on it. They snap/split easily with a little weight from snow or even wind storms. This seems to be an inherent problem with this pear.

A "house call" to see your tree in person is probably necessary to see exactly what is going on and potential causes.

Regards
Steve

---------- FOLLOW-UP ----------


Chinese Pistachio Tree   QUESTION: Thank you for the response,and I regret not being able to send you few more photos since you limit to one image.  Is there any other e-mail address that I can send you further photos that showing the problem with the tree?
If yes, kindly send me your exact information..In the meantime I am attaching one image that might help.
Thank you
Nancy Davis

Answer
Nancy:
Another email address to use: [email protected]

Please put Chinese pistachio in the subject line.  
Any wounds in the bark and underlying tissues can result in this sap flow. Things like weather extremes, insects (usually borers), and mechanical wounds can result in this flow. Not always obvious as to the cause of these wounds.

Regards
Steve