As the global population increases (trending towards 9 billion people by 2050), it is anticipated that food production will need to increase by 70 percent to meet global demand. Sustainable agricultural practices will increasingly be needed as the industry seeks to minimize its human and ecological health impacts while scaling and providing for this demand. One of the biggest areas that chemistry influences agriculture is pesticides. Greener pesticide technologies are catching on more and more, and in particular, biopesticides (a market that is projected to grow to $4.5 billion in 2023).
Early pesticides were typically highly toxic materials (e.g., Arsenic) or synthetic organic compounds (e.g., DDT). Some of these conventional technologies faced government phase-outs (due to their toxicity, persistence, or insolubility) or pest resistance. Public concern over pesticides had a strong influence in shifting away from some of the more toxic pesticides over the last several decades. In general, since then consumers have been pushing chemical markets towards natural products (though it is important to remember that not all natural products are safe).
Biopesticides are a certain type of natural product that are used to control pests, plant diseases, and weeds. The two major categories of biopesticides: biochemical and microbial. Biochemical pesticides control pests with naturally occurring substances such as insect pheromones, plant extracts, and plant or insect growth inhibitors. Microbial pesticides use microorganisms as the active ingredient (bacteria, fungi, viruses, and protozoans). (Transgenic crops (also known as plant incorporated protectants) are also technically considered to be biopesticides, where scientists modify a plant’s genetic material with specific pesticidal proteins, but will not be addressed in this post). The primary advantages of these biochemical and microbial bioproducts are that they are usually less toxic than conventional pesticides, affect only the target pest, can be used in very small quantities, and can decompose quickly. On the flip side, they typically have shorter shelf lives, limited persistence, and can be slower acting.
The U.S. EPA’s Presidential Green Chemistry Challenge Award (PGCCA) has been granted 13 times to innovators who have developed greener pesticides. Seven of these technologies are considered biopesticide-related or are processes that support the bioproducts’ pipeline. For example, in 1997 two professors from Michigan State University won the academic award for developing genetically engineered microbes and a process for synthesizing catechol (a building block for many pesticides that is usually derived from petroleum-based benzene). Another notable award is the 2001 Small Business Award to EDEN Bioscience Corporation (since then the technology has been acquired by Plant Health Care, Inc.). The team developed and commercialized harpins, a new class of proteins produced by plant pathogenic bacteria. Without altering the plant’s DNA, harpins can activate the natural defense mechanisms of the plant, fight disease and pests, and trigger the plant growth systems. This technology is not only considered non-toxic, but is produced via an essentially waste-free water-based fermentation process.
Another challenge that biopesticides can face is that they can unknowingly affect a broader spectrum of non-target species. One example is spinosad, Dow Agroscience’s 1999 Designing Greener Chemicals PGCCA Award. The product is developed through a particular soil microorganism. It was highly effective on specific species, and had a favorable environmental profile with low tendency to leach, persist, bioaccumulate, or volatize. (In 2008, Dow Agroscience won again for a spinosad development—spinetoram, a more effective equivalent biopesticide for tree fruits and nuts). While spinosad was significantly safer for humans, in the early 2000’s it was discovered that it was intrinsically toxic to pollinators.
It is clear that biopesticides are a key tool for more environmentally benign agricultural practices, but not without some issues to always be aware of. Like all greener chemistry innovations, there is a constant thrust for continuous improvement and deeper understanding of what hazard means in this field. In addition to products to be applied directly to plants, there are biopesticide treatments being developed for seeds and soil amendments. Through multidisciplinary collaborations (between chemists, entomologists, toxicologists, etc.) these products can continue to grow in safer, holistically understood ways and support more sustainable agriculture.
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