Question
Hello David, How can I treat a 7 year old Japanese Pistachio tree that has had verticillium wilt for two years now?  The leaves turn yellow, then curl to brown, then fall off.  Only the twig is left.  It only takes about three weeks.  The tree is in Albuquerque, New Mexico, a high dessert.  The 1st sign of yellowing appeared on June 20th.  Now half the tree has lost it's leaves.  It was also affected, less severely, in July of last year.  In Spring it was full and deep green.  This year has been a very good year for rain and a summer of mild temperatures.  Thank you.


Answer
If you are sure the tree has Veticillium wilt, there is no cure or effective treatment for the vascular fungal disease.  Many times with other crops a deficiency in potassium will make the problem worse.  You may try fertilizing with a fertilizer such as 0-0-60 at the rate of about 1 lb spread around the drip line of the tree.  If the tree is declining further each year, it is unlikely that you will be able to save it.  If you get another one, do not plant it near the existing tree as the disease may move to the new one.  Good Luck.