Bioacoustic Studies                                            Hofstetter Lab homepage

    Because of the extraordinary economic and environmental impact of bark beetles it is critically important to better understand the factors that influence beetle dynamics and to improve management tools that can reduce beetle populations.  Despite considerable research on bark beetles, our comprehension of the mechanisms that contribute to host tree selection and beetle population growth remains limited and our management options to control beetle populations are few.  A missing piece in our knowledge of bark beetle ecology is their use of acoustic cues to find resources and mates.  Visual and olfactory cues are important for host finding and mate recognition, but the use of these senses for management tools have been expensive and limited in their efficacy.

      Many entomologist and botanists propose that acoustic emissions from trees attract herbivores and predatory insects, such as bark beetles.  We know that many tree-infesting insects have well-development acoustic senses, but we have yet to experimentally prove that bark beetles use sound to locate susceptible trees.  Most bark beetles attack and colonize trees that are stressed by drought, extreme temperatures, wounds, or lightning.  Interestingly, during drought conditions plant cells begin to break (called cavitation) which release acoustic emissions that have both an audible range (<20 kHz) and an ultrasonic range (up to 2000 kHz). It is known that ultrasound within 20-200 kHz is produced and detected by many insect species.  We believe that bark beetles produce, detect, and utilize sounds in the ultrasonic range and likely utilize drought-induced acoustic emissions to find trees.

      Our research team studies the possible connection between ultrasound emissions in plants and utilization by bark beetles.  This technology will (1) lead to methods of controlling bark beetles in an efficient and cost effective manor, (2) advance our knowledge of bark beetle ecology, and (3) open up a the field of acoustics in insect research. Technologies used to effectively control bark beetles would be a multi-million dollar industry.  Bark beetles are the most significant pest of forest and forest products world wide, resulting in billions of dollars lost in annual revenue every year.

OBJECTIVES OF RESEARCH:

We plan to deploy sound as a mechanism to (1) capture bark beetles, (2) deter beetles from actively colonization pines, (3) confuse beetles currently colonizing pines in an attempt to prevent further entry into trees, and (4) reduce the survival of larvae already developing within infested trees.  The advantage of sound as a mechanism of beetle control has many compared to current methods of beetle regulation and prevention; first, the effects of sound are species specific.  In other words, sound will only target the bark beetle species within the local area (i.e. meters surrounding the tree) and will not interfere with other organisms and non-target species within the forest community. Second, the use of sound is non-toxic.  Third, the use of sound will have no affect on trees and other living plant material within the forest community. Fourth, the forest is left unaltered both physically or chemically, and fifth, ultrasound would not be heard by humans and could be used in human habited areas.