What Are Ips Engraver Beetles Telling Us About Our Pines
A landowner looks across their property and notices the pines that just last week seemed to be green and full of life are now brown and lifeless. All signs point to an infestation of pine bark beetles. Fears mount that these trees have fallen victim to the dreaded southern pine beetle (SPB). A closer look finds that SPB are not present, but another bark beetle, Ips engraver beetle, or Ips for short, has invaded the tree. The focus now turns to Ips as the accused killer of the once stately pine trees.
Ips in gallery. Photo by Jamie Dunbar, NCFS
It is important to get a sound diagnosis since management or control of bark beetles depends on the species present (there are three main species that affect pines in North Carolina: SPB, Ips, and black turpentine beetles). Typically, Ips affects individual or small groups of trees but can be implicated in larger infestations when pines in a forest or landscape die, seemingly overnight. To diagnose, rangers, foresters and arborists will peel bark off impacted trees looking for tell-tale signs of bark beetles. A sign of Ips is galleries (or tunnels) under the bark that are clean and finely etched or engraved into distinct “X”, “Y”, “K” or “I” shapes. These should not be confused with SPB galleries that are sloppy “S” shapes and filled with wood dust. If an adult beetle is present, a magnifying glass may aid in confirming its identity. Ips species are very small and have depressed or concave hind ends. They look like some bigger bug took a bite out of their behinds.
Ips avulsus. Photo by: J.R. Baker & S.B. Bambara, North Carolina State University, Bugwood.org
Once Ips is diagnosed in a tree, only half of the puzzle is solved. Remember, Ips are opportunists so something else caused the tree to be damaged or stressed in the first place. Lightning, prolonged drought or flooding, as well as damaging ice and wind storms are natural tree stressors that often precede Ips attacks. Trees can also be stressed by human activities, and secondary pests like Ips often tell us we are not treating our trees right. When we have positively diagnosed Ips, but cannot pin the cause of the infestation on a natural event, it’s time to pull out an unlikely investigatory tool, a hand-held mirror. Looking at the image in the mirror, one should ask, “did I do something that stressed my trees, or did I give my trees the best chance to grow healthy and strong?”
Some ways we stress our trees, often without knowing it, are:
Forgetting about the roots. Usually we only think about the part of the tree we see; the part above the ground. However, it is estimated that 20 percent of a tree is underground in the root system. Roots can be stressed or killed by lack of drainage, compacted soil, grade changes, or mechanical damage. Root loss creates an imbalance that causes the tree tops to suffer also.
Not thinking like a pine. Ask any pine and it will tell you it is happy when you give it plenty of sun, leave its roots alone, and let the organic forest floor provide it with life giving nutrients. They won’t talk about it often, but pines despise being forced to coexist with turf grasses, which are fierce competitors for water and nutrients in the soil. Most pines like a little bit of competition but will complain that turf grasses do not play fairly (turf grasses feel the same way about pines). If given a choice, pines prefer a natural forest floor or a mulched landscape understory over manicured lawns.
Lack of room to grow. Thinning is important to pines. Historically, fires and insects killed weaker trees and opened forest canopies for healthy pine crowns to spread out. If you don’t thin your pine stand, Ips will thin it for you, and you might not like the way they do it.
Now put down your magnifying glass and mirror, and take a walk in the forest. Be sure to ask your trees what they need. And don’t let Ips finish the sentence for the pines. If you need help, or have trouble understanding tree language, call your county ranger and ask them to translate for you. They can get you started with a plan to grow healthy, happy trees. Contact information for local N.C. Forest Service offices can be found at: http://www.ncforestservice.gov/contacts/contacts_main.htm