CONICET | Buscador de Institutos y Recursos Humanos

At a time when chemical control of noxious insects was seeing as close to a panacea (early 1960s) few had the foresight to look for viable alternatives. Among those few was Dr. John E. Henry who not only appreciated the environmental problems posed by chemical insecticides but also put his hands on finding ways to keep grasshoppers at bay without relying on synthetic insecticides. After years of meticulous field observations on grasshopper communities and their natural enemies in northwestern USA and laboratory experiments at the USDA Rangeland Insect Laboratory at Montana State University in Bozeman, he and collaborators opted among several other candidates discovered for an unlikely microorganism to be developed as a biocontrol agent for the long-term management of grasshopper populations. Paranosema (Nosema) locustae is indeed a rather unique microbial within a quite unique group of fungal-affiliated, spore-forming intracellular parasites of animals and some protists, the Microsporidia. It infects primarily the cells of the host?s adipose (fat) tissue causing depletion of energy reserves and alterations in intermediate metabolism. Uniqueness of P. locustae, conferred by a set of attributes, was unraveled by Henry during his studies and exploited to its maximum in order to end up with a useful tool for grasshopper management. Few if any of the approximate 1500 known species of Microsporidia show the combination of attributes of P. locustae: extremely wide host range among acridomorphs (at least 123 species worldwide are susceptible to infection) which allows use against a variety of pest grasshopper species, efficient horizontal and vertical transmission facilitates long-term field persistence, intermediate virulence permits heavy spore loads per individual host, and good tolerance to freezing enables storage for extended periods (years). Two drawbacks, the apparent impossibility of in vitro production and the low viability of spores under field conditions were cleverly circumvented by establishment of protocols for in vivo production in grasshopper colonies and the use of baits for field delivery, respectively.The narrative that follows, ?The path to registration of a microbial pesticide? by Henry himself, is a concise account of the reasoning and work that lead to the development and registration (1980) of P. locustae which holds the distinctions as both the only microsporidium to reach that status and the first organism that become available as a biocontrol agent of grasshoppers. Henry?s work and approach was not only innovative (especially at its time) and lasting but also truly international in scope and repercussion. It was innovative because it departed from the environmentally disrupting application of indiscriminate, fast-killing chemical insecticides. International because it prompted interest and programs worldwide (notably China, West Africa, India, Argentina, Australia) not only about the use of P. locustae itself but also about the discovery of other pathogens and on environmental friendly initiatives based on his approach that disease-causing microorganisms would be useful for grasshopper management. In the words of acridologist J. A. Lockwood ?Research, development, and marketing of biological control strategies for acridid pests have been and will be affected by the history of P. locustae?. In fact the development of a second biocontrol agent during the late 1980s and early 1990s, the fungus Metarhizium acridum, widely used in Australia, was greatly inspired and influenced by Henry´s pioneering work. In recent years there has been a resurgence of interest in P. locustae due mainly to work in China, where it is produced in large quantities and used extensively, and Argentina where its long-term persistence seems to reduce the frequency and intensity of grasshopper outbreaks. We hope the reader enjoys the narrative by J. Henry and appreciates the innovative and pioneering work performed on a very unusual microorganism.