Q: My yard has a palo verde borer beetle infestation. I have personally smashed/stepped on/killed this many the last three years: 2014 – 54, 2015 — 53 (June 18-July 21), 2016 — 66 (June 19-July 31). I documented how many per night. And documented male/female numbers.Front yard has a 12-year-old Desert Museum palo verde with the most infestation. It lost a quarter of its branches this fall. Backyard has a 30-plus-year-old ash tree. In 2016, 28 of the 66 were from the ash. I tried two applications of beneficial nematodes (September 2015 and April 2016) with no reduction. Any help and suggestions are welcomed.
A: Palo verde beetles are typically an indicator of a stressed tree. They are often found when dead palo verde trees are removed but they are rarely responsible for the death of trees. Trees often die of multiple causes including the many environmental factors they are exposed to in our landscapes. It is usually these stresses and other factors unrelated to the beetles that cause tree death, even when the beetle larvae are present feeding on the roots. My suggestion is to make sure you are doing everything you can to care for your trees. This will go a long way toward protecting them from an early death. Beneficial nematodes are a wonderful thing in the right circumstances but there is no research I am aware of that shows they have any affect on palo verde beetle populations.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Email questions and photos to tucsongardensage@gmail.com
