Back in 2001-03, the Four Corners region was in the midst of a large pinyon ips outbreak due to a drought, but most of the pinyon death was farther south of us. Having driven through the region recently it appears that ips outbreak left considerably fewer pinions, and now we see more of a juniper “forest” than a mixed pinyon and juniper forest. While there are other borer beetles that will attack pinyons, such as the mountain pine beetle, they are secondary to the pinyon ips.
The pinyon ips beetle is a small dark, blackish beetle about the size of a grain of rice. As with all of our current borer type insects, they go after stressed or damaged trees. The biggest stressor we experience is drought that leads to limited soil moisture and tree stress. While there are always some pinyon ips beetles attacking trees here and there, having widespread drought stress leads to an increase in the number of beetles and allows them to mass attack trees. The beetles tunnel under the bark, mate, lay eggs, and the larvae tunnel into the cambium and phloem layers under the bark. These layers are the parts of the tree that move water and nutrients and this tunneling kills the cambium and phloem disrupting that movement.
A major sign the pinyon is infested by ips beetles include pitch tubes that are often described as reddish popcorn-shaped masses. The trees I looked at after October’s rains had pitch tubes but they had been partially washed away. When high numbers of ips beetles have attacked a tree you will also see frass or wood dust down the trunk or around the base of the tree. Once infested, the needles on the tree turn from green to a light pale yellow to red and then brown.
Controlling any type of boring insect isn’t easy. Pinyons with multiple pitch tubes are not likely to survive, and trees that have reached the stage where the needles have started changing color aren’t going to survive. To stop beetles from infesting a tree the best control measure would be to use a preventive spray of insecticides labeled for bark beetles that would include carbaryl or permethrin. Beetles will become active in the spring when daytime temperatures are averaging 60 degrees. Usually three generations of beetles are produced annually. You would spray the trunk and any limbs of one inch diameter or larger and the general spray schedule would include a spray by April 1, July 4 and Labor Day in September.
Other control measures would include watering the most important non-infected pinyons around your home during periods of drought to mimic natural rainfall. In an area with large numbers of pinyons and junipers, removing some of the trees or junipers would allow those remaining better access to any available soil moisture. To help limit the number of beetles next spring, since the beetles will overwinter under the bark of infested trees, you can cut them down and chip or burn them, or cut and debark the trees exposing the beetles, or cut into sections and cover with clear plastic, which is called solarization. Considering the number of trees already infested, the expectation would be that more trees will be infested next spring due to the already large number of bark beetles.
The bottom line is that these things do happen. Drought isn’t new to the Four Corners regions. Tree ring records show many droughts in the past, some appearing to show more severity. We will definitely lose many pinyons but hopefully some will survive to allow a renewal at some point in the future.
Previous articles can be found on The Times-Independent website. If you have a topic you would like to know more about call the Utah State University Extension Grand County office at 259-7558 or email Mike at email@example.com.