Predicting lifecycle timing and infestation patterns of the pinyon ips bark beetle
Pinyon ips - caused tree mortality on the Cibola National Forest
In the western United States where hot droughts can stress plants, wildlife, and humans alike, another challenge is facing pinyon pine trees: the “pinyon ips” bark beetle. These native bark beetles attack pinyon pine trees and can cause extensive tree death, particularly during times that trees are already stressed by drought. However, until now, the beetle’s life cycle responses to temperature variation were uncertain.
Scientists from the USDA Forest Service’s Rocky Mountain Research Station, Utah State University, and the USDA Forest Service’s Forest Health Protection program stepped up to the challenge and initiated a study of the pinyon ips life cycle in response to temperature variation. They monitored the beetle’s lifecycle timing by measuring attacks on trees and using cages to observe adult emergence, in addition to traps that record adult flight at field sites in Arizona and New Mexico. They also monitored beetle development under constant temperatures in the lab. Using the data they collected, the scientists developed statistical models that can predict pinyon ips lifecycle timing and infestation patterns which is a key piece of information needed to predict future tree mortality.
A pinyon ips "gallery" is visible under the tree bark
A major outcome of this study is that the scientists’ statistical models can be used to estimate pinyon ips generation time based on daily temperature records. This means that land managers with access to daily temperature records at a site can now predict patterns of pinyon ips infestation since warmer temperatures can yield more pinyon ips generations within a single year, potentially yielding more tree death. As hot droughts continue to be a concern across the western United States, this new information can help to target mitigation efforts.
Pinyon ips populations can buildup in slash piles and emerge to attack and kill nearby living trees. Current guidelines recommend that pinyon pine woodlands are thinned in the fall to ensure that slash left on the ground is not green when the beetles are active and able to infest it. However, this research indicates that the thinning and slash production window may need to be shorter in some areas if temperatures remain high enough to support additional pinyon ips generations.