E-Beam Treatment of Invasive Species

M. Geelhoed
Fermi National Accelerator Laboratory,
United States

Keywords: invasive species, wood burrowers, e-beam

Summary:

Fermilab researchers are developing and demonstrating a new class of portable particle accelerators that can treat trees infested with Emerald Ash Borer (EAB), an invasive beetle that preys on forest resources. With sufficient development, this technology can be brought to address additional invasive species beyond EAB. The technology can be used to slow the spread of existing invasive species within the United States while preventing the introduction of new wood burrowers in the first place— offering a new tool for invasive species management. The list of invasive species within the United States is ever increasing based, in part, on international trade demand. Once a species settles and expands, the impact can cost millions of dollars. An attractive solution for slowing the spread of certain types of invasive species is electron beam (e-beam) accelerator technology. E-beam can provide a safe, environmentally-friendly and cost-effective alternative to traditional methods of treating trees infested with wood burrowing invasive species. Infested trees are a loss in the forestry industry that, if treated effectively for infestation, can serve as a source of goods such as furniture and construction materials that would otherwise go to waste. “Wood burrows,” such as the Emerald Ash Borer (EAB), make up most invasive forest pests. These beetle species lay eggs on the bark of the host trees in which larvae burrow between the bark and the sapwood and pupae further develop. In this layer, they create serpentine paths, which disrupt the flow of nutrients, eventually killing the tree. This invasive species has been detected in the US. Numerous studies conclude that, for in-air irradiating, the sterilization dose ranges from 43 to 200 Gray (a unit of radiation defined as the absorption of one joule of radiation energy per kilogram of matter). Ionizing radiation is typically delivered in three ways: gamma source, x-ray or electron beams. Electron beams have become a more efficient alternative to ionizing radiation and have the depth of penetration required for phytosanitation. The depth of penetration of an electron beam is determined by the energy of the electron and density of material. Agencies regulating e-beam accelerators place a cap on this energy of less than or equal to 10 MeV. With this energy, given the material density of wood, electron particles have a depth of penetration of 2.5 inches. If the average thickness of bark is 2 inches, the electron’s range will interact with the pupae and larvae. The next generation of electron beam accelerators— enabled by superconducting materials and advanced power sources— will be smaller, more portable, and highly efficient. Fermilab scientists and engineers are developing and demonstrating this new class of portable-yet-powerful particle accelerators. E-beam technology is an additional tool in the toolkit to implement a safe and proven process in a novel manner. Invasive pests like EAB are a nuisance, and steps have been taken to slow, stop, and remediate infestation— yet this emerging technology can expand beyond EAB and potentially address other invasive pests, not if but when they spread.