MAGNETICALLY INDUCED CURRENTS FOR SELECTIVELY DESTROYING PINE BEETLES IN SITU (“SAPZAP”) 1. Department of Electrical and Computer Engineering, 2. Neuroscience Program, Howard Wachtel 1,2 & Frank Barnes 1 University of Colorado Boulder CO USA

Outline of Talk 1. Introduction to Problem 2. Approach Using RF 3. Some Power Calculations

The Problem Ravishing huge stands of lodgepole pine Colorado Rocky Mountains, west slope and elsewhere Expected to cross the continental divide Destroy millions of trees along the Front Range The Mountain Pine Beetle (MPB) "Dendroctonus Ponderosae“ Image from:

The Problem Image: Once a tree has been infiltrated by MPB "conventional wisdom" holds that it cannot be saved So, often the first sign that beetles have entered is also the "death knell" of the tree.

The Solution Image: We believe that coniferous trees can be rescued if the MPB can be selectively destroyed within the tree An approach to this may be to deploy highly selective hyperthermia.

Coniferous Tree (Pine, etc.) Characteristics -- Cross Section The bark (outermost layer) The next layer (xylem) The innermost layers (growth rings or cortex) The xylem layer. "blood supply" of the tree. Interruption of sap flow completely around the xylem circumference will inevitably lead to the death of the tree. Usually quite dry and has a low electrical, as well as thermal, conductivity. quite wet (sap laden) and high in electrolyte content so it is much more conductive. relatively dry and low in conductance.

Coniferous Tree (Pine, etc.) Characteristics Evidence, mainly from controlled forest fires ("burns") suggest that coniferous (pine, etc.) trees can survive fairly high temperature elevations as long as the xylem temperature does not exceed 60 o C for an extended time period.

Mountain Pine Beetle (MPB) Characteristics Adult MPBs – can bore through the bark of certain pine trees (especially lodgepole) – settle in the xylem where they carve out "galleries” into which the females lay eggs—and these hatch into larvae which remain in the cambium. The MPB (and their larvae) – Produce a blue colored fungus, which spreads through large portions of the xylem, – Fungus will block sap (nutrient) flow and this will kill the tree.

Mountain Pine Beetle (MPB) Characteristics Logs cut from beetle infested trees have been "decontaminated" by thermal means including microwaving, solar heating, etc. Temperatures in the range of 45 to 55 o C have been reported to be effective in killing MPB and similar insects. Similar temperatures might reasonably be expected to be lethal to MPB within living trees.

Energy Considerations for Hyperthermal Treatment of MPB Infested Trees We hypothesize that an elevated cambial temperature of about 55 degrees C, sustained for several minutes to an hour or so, will selectively destroy MPB and their larvae while doing only minor damage to the tree.

Energy Considerations for Hyperthermal Treatment of MPB Infested Trees A tree that has 1 meter length and 30 cm diameter The sap layer has a circumference of about one meter and a typical thickness of 0.5 cm The sap volume (xylem) is about 5000cc. Energy required to raise its temperature from say 25 o C to 55 o C would be 150,000 joules ( ~650,000 watt-seconds). Assuming no heat dissipation from that xylem layer

Energy Considerations for Hyperthermal Treatment of MPB Infested Trees This could be achieved, for example, by inputting 6500 watts for 1000 seconds (17 minutes). Taking into account thermal losses (cooling) to adjacent layers as well as source inefficiencies might reasonably double or triple this figure—but this still is within the realm of feasibility.

Pine Tree Forest

Possible Coil on Tree ~

Dielectric Constant as a Function of Depth into Tree [1]

Electric Field as a Function of Radius and Frequency Calculation s N=10 I=10 f= Hz r c =5.5 cm

Conductivity as Function of Distance From the Surface.  r (mm)

E as Function of Distance From the Surface. r (mm) E

Power Density as Function of Distance From the Center r (mm) P

Work in Progress and To Be Done 1. An RF 1KW source at 13.5 MHz has been located and is being prepared for testing. 2. Short sections infected logs will be acquired from the Forest Service. 3. We will run tests on “zapping bugs” and measuring temperature profiles. Acknowledgement to Seyitriza Tigrek for help in preparing the power points.