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An introduction to the main techniques of biological pest control

Updated: Dec 14, 2021

Every year, millions of gallons of synthetic pesticides are applied to crops worldwide, with a well-known negative effect on the quality of the final product as well as on the quality of the surrounding ecosystems. The reasons behind their intensive use are the same behind the usage of synthetic fertilizers: convenience (real or assumed), a lack of viable alternatives, and a strong cultural and educational bias in favor of their use. But this is all changing, and changing fast, with the diversification and massification of biological means for pest control: in a 2017 paper, a team of researchers from the Netherlands, Belgium and Spain found that while the synthetic pesticide market was consistently growing at a yearly rate of 5-6%, the biological control market was exploding at yearly growth rates of 10% before 2005, and 15% afterward.

In light of these recent developments, it’s important to get an introduction to the three fundamental forms of biological pest control: classical techniques, augmentative techniques, and conservationist techniques. In each of these three techniques, a species or a group of species is deliberately released in a cropland area to serve as predators of another species, which is acting as a plague. The real variations come from the details.

Classical techniques of pest control have been used since the 19th century at least, when the famous American entomologist Charles V. Riley saved the blossoming citrus industry in California from a plague unwillingly imported from Australia (the scale insect Icerya purchase) by willingly importing a predator from the same country, the vedalia ladybug (Rodolia cardinalis). These classical techniques consist in basically this: importing and establishing a foreign predator to deal with a foreign pest. Riley introduced the ladybugs in 1872, and this sight became common in citrus plantations across the state:

Augmentative techniques are different, in the sense that they do not seek to establish the predator that is imported as a means of biological control but simply release it in numbers that are large enough to destroy or severely reduce a plague in a determinate moment. Consequently, these augmentative techniques (augmentative precisely because they seek to simply augment the number of predators for a while) are often repeated in regular schedules, much like in the way that seasonal applications of synthetic pesticides are carried out (but still without the many negative effects of such pesticides). The species introduced here as biological control can be foreign or local.

Augmentative techniques, however, have one important flaw: they tend to work less well in ecosystems that lack diversity, as most agricultural spaces are. Another team of researchers, this time from Cornell University, noted in a 2019 paper that the efficacy of such methods is greatly influenced by the biodiversity of the areas where they are applied.

Conservation techniques of biological control become the solution for these problems, as well as for the repeated cost of releasing predators seasonally. Acting from the standpoint of integrated systems management (seeing agriculture as not the exploitation of space and resources, but as the task of stewarding a system that produces food according to certain inputs, and to the management of certain variables), these techniques of biological pest control try to improve the overall suitability of the ecosystem where the predators are released, in order to allow them to get fully established and working year-round, ideally without a need for further introductions. The need for increased biodiversity in the fields is also tied, perhaps not surprisingly, with the current lack of diversity in the food we grow.

Biological means of control are not new, but they are being newly introduced to many farmers and spaces where and by whom they haven’t traditionally been used. Like in conservation techniques for their management, the economic ecosystem is full of opportunities for their establishment, and, consequently, for their growth. So it’s about time we all got acquainted with the critters and microorganisms that save the food we eat – and that’s what we’ll be talking about, in upcoming entries. To cite van Lenteren, Bolckmans, Köhl, Ravensberg and Urbaneja from their 2017 paper referenced above:

"Too often the following reasoning is used to justify the use of synthetic pesticides: agriculture has to feed some ten billion people by the year 2050, so we need to strongly increase food production, which can only be achieved with the usage of synthetic pesticides. This reasoning is simplistic, erroneous, and misleading. Simplistic because it ignores a multitude of other approaches to pest, disease, and weed control that we summarize below under IPM, erroneous as sufficient healthy food can be produced without synthetic pesticides (...) and misleading in that it minimizes the importance of a well-functioning biosphere and high biodiversity for the long-term sustainable production of healthy food for a growing human population (...). This short-sighted mercenary attitude might actually result in very serious environmental problems in the near future (...). A more sensible approach to food production is to ask ourselves: (1) how can we create a healthy and well-functioning biosphere in which biodiversity is treasured instead of strongly reduced, both because of its necessity for sustainable food production and maintaining a hospitable biosphere for humans (utilitarian approach), as well as because of our ethical responsibility (ethical approach), (2) how can healthy food best be produced in this well-functioning biosphere, and (3) what kind of pest, disease and weed management fits in such a production system."


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