Canadian contributions to forest insect pathology and to the use of pathogens in forest pest management

Abstract

The study of insect pathogens became established as a distinct discipline in the late 1940s. In the ~65 years that followed, forest pest management was the main theatre for the development and practice of insect pathology in Canada. Researchers from the federal government and academic institutions contributed to the growing discipline by acquiring foundational knowledge on taxonomy, mode of action, natural occurrence, and ecological role of key pathogens infecting forest pest insects, covering an array of fungi, Microsporidia, viruses, and bacteria. The ultimate goal was to develop pathogen-based alternatives to synthetic insecticides used in large-scale forest protection programmes throughout eastern Canada. That goal was achieved through the development of baculovirus-based products for control of gypsy moths (Lepidoptera: Erebidae), tussock moths (Lepidoptera: Erebidae), and various sawfly (Hymenoptera) species, which are now in the hands of private industry and poised for growing operational use. The second success was the development of products based on Bacillus thuringiensis Berliner (Bacillaceae), which have almost entirely replaced synthetic insecticides in forest protection. We review those successes and other key Canadian contributions to forest insect pathology within the context of emerging digital, molecular, and other technologies, and show how they have altered today’s face of forest pest management in Canada.

A history of biological control in Canadian forests, 1882–2014

“…The Belleville laboratory closed in 1972 as part of broader reductions across the federal government, and this severely constrained the resources available for forestry programmes. At the same time, aerial insecticide programmes expanded exponentially with focus on both chemical and biological applications (reviewed by Holmes andMacQuarrie 2016 andvan Frankenhuyzen et al 2015). Biological control projects that began after 1970 were of much smaller scope than earlier.…”

“…Despite this massive effort, classical biological control agents were not responsible for the eventual decline of the European spruce sawfly, but instead it was attributed to a nucleopolyhedralvirus, GhNPV (formerly Borrelinavirus hercyniae), brought in with agents during the 1930s (Bird and Elgee 1957). This virus spread quickly to wild European spruce sawfly populations causing significant mortality (Bird and Elgee 1957), and resulted in a shift in biological control work to mass-production of GhNPV (reviewed by van Frankenhuyzen et al 2015). The virus became so successful that by 1943, classical biological control was scaled back to only production and release of a few agents.…”

“…In the following review, we define biological control as the manipulation of natural enemies (vertebrate, invertebrate, or microbial) to reduce pest populations below an acceptable level of damage (van Driesche et al 2008), and focus solely on the use of arthropods and vertebrate animals. Microbes are dealt with in a related review (van Frankenhuyzen et al 2015).…”

Previous exposure to myxoma virus reduces survival of European rabbits during outbreaks of rabbit haemorrhagic disease

“…In addition to their obvious importance for human health and animal conservation, disease synergies could potentially influence the efficacy of biological controls for invasive species. Pathogens such as macroparasites and viruses are often used for biological control of invasive animals and plants (McColl, Cooke, & Sunarto, 2014;van Frankenhuyzen, Lucarotti, & Lavallee, 2015), and their impacts on the invasive host can be mediated by co-infections with other pathogens (Boag, Hernandez, & Cattadori, 2013;Cattadori, Albert, & Boag, 2007). Synergies can occur between a biological control agent and (a) pathogens introduced with the invasive species, (b) pathogens that occur naturally in the invasive range, or (c) another biological control agent introduced to reduce the abundance of the same invasive species (Boag et al, 2013;Lello, Boag, & Hudson, 2005).…”

Aerial spraying of bacterial insecticides to control spruce budworm defoliation leads to reduced carbon losses

“…, van Frankenhuyzen et al. ). For example, from 2006 to 2016, over 2 million ha of forests were aerially sprayed with insecticides in Canada, 82.02% of which was Btk (Canadian Council of Forest Minister ).…”