Defoliating Pinon Pine Trees?


If your Piñon pines appear to be ailing and you live in New Mexico, it’s possible that your trees are infested with Piñon Needle Scale. Do your piñon trees look like they have lost half their needles? Do the underside of the needles have small black spots? These spots are most likely caused by Piñon Needle Scale nymphs. The nymphs insert themselves onto the Piñon’s needles, cover their bodies in wax, and turn black, while in the process, suck the sap from the needles and seriously weaken the tree. Once the scale bugs are embedded into the needles, they are very difficult to control, the trick is to get to them before they embed themselves into the piñon pine’s needles.

In Santa Fe, the male piñon needle scale bugs emerge in the fall and spend the winter in the litter beneath the tree. The adult wingless females emerge from their scale covering sometime between mid-March and mid-April, are fertilized by the males, then lay their eggs.  This is the time to look for scale because after the females lay their pale yellow eggs in clusters which are held together by a white webbing clustered around the base of the piñon tree and along the underside of the piñon trees branches. If the eggs are left undisturbed, the eggs will “hatch” in about 4-6 weeks time and the nymphs or crawlers will travel to the ends of the piñon’s branches and settle into the previous years needle growth.

The trick is to interrupt this process by destroying the eggs before they hatch. The egg masses can be dislodged from the trunk and branches of the tree with a high pressure nozzle on a garden hose, assuming of course you have a garden hose long enough to reach the ailing piñon. The material should then be raked up around the base of the tree and destroyed or removed. Ideally, the pine needle duff that has been removed from under the trees would be replaced with an organic wood or bark mulch which will aid in holding moisture on site and improving the overall health of the piñon pine. The piñon will appreciate any efforts made to retain stormwater on-site (in addition to the application of mulch) including passive stormwater catchment strategies, such as terracing, swale & berms, and stone gabions.  The additional moisture rentention helps piñon trees in their fight against the weakening agents of Piñon Needle Scale and drought.

Here is a very informative interview conducted by Dona Ana county extension agent, John White, with Bob Cain, a Santa Fe extension Forest entomologist, which I found on the New Mexico State University website, it is one of the videos in their Southwest lawn and garden “How to” series.