A New “Pesticide”

The agriculture industry is one of the largest and most vital industries in the United States, providing food security, jobs, and economic growth to many people all over the country. However, for decades, it has faced a dire problem: finding safe and effective ways to protect plants and crops from pests such as insects, rodents, and fungi. Historically, chemical pesticides—chemical constituents used to prevent or control pests—have been the answer, but times have changed. Despite their advantages in crop production, traditional pesticides pose significant hazards to the environment and public health.

Pesticides have existed for thousands of years, dating back to 2500 B.C., when ancient Sumerians used sulfur compounds to kill insects. However, beginning in the 1940s, chemists and companies began producing synthetic organic compounds that took over the pesticide market. These synthetic compounds have contaminated food, water, and soil, producing various forms of toxicity and increasing risk for various diseases. According to the World Health Organization, three million people worldwide are affected by pesticide toxicity, with 200,000 dying each year due to pesticide exposure, primarily in developing countries. The chemical makeup of pesticides contributes to the production of reactive oxygen species, which decreases levels of antioxidants (molecules that help your body fight free radicals) and their ability to protect cells from oxidative damage. This creates an imbalance between free radicals (highly reactive, unstable oxygen molecules) and antioxidants, which leads to cell, protein, and DNA damage in humans. This oxidative stress is associated with the onset of various diseases, including cancer, kidney disease, and neurological diseases. Thus, scientists have been looking for a safer alternative to pesticides.

One of the most promising alternatives to conventional chemical pesticides is RNAi-Based Pesticides, which were made possible by a breakthrough in the field of genetics regarding RNA interference (RNAi). RNAi is a method where small pieces of RNA can inhibit protein translation by binding to the mRNA that codes for the proteins. These small pieces of RNA, which include siRNA and miRNA, bind to Argonaute proteins, forming RNA-induced silencing complexes. These complexes bind to mRNA and prevent the ribosome from translating the mRNA into proteins while signaling the mRNA for destruction via endonucleases. This means that the proteins essential for the pest’s survival cannot be produced, resulting in the death of the pest. 

The specific function of RNAi Pesticides is to target a specific survival gene present across many species of pests. There are two forms of RNAi pesticides: plant-incorporated protectants (PIPs) and non-plant-incorporated protectants (non-PIPs). The first marketed use of RNA pest control was in the form of genetically modified western corn (PIPs), which targeted snf7, a gene found in rootworms that encodes a protein necessary for its survival. When the rootworm ate the genetically modified corn that was able to encode the RNAi targeting snf7, the rootworm’s cells were no longer able to produce the transport protein snf7 encoded for. By genetically modifying a crop to encode RNAi, many downsides associated with synthetic organic pesticides were eliminated. However, genetically modified crops take years to produce and are expensive due to the extensive amount of research and testing required. This means that genetically modifying every crop affected by pests is not a feasible option.

As a more accessible and less expensive alternative to genetically modified crops that encode RNAi, RNA pesticides are also being produced as sprays (non-PIPs). One of the first applications of RNA-based pesticide spray was to target the Colorado Potato Beetle, which damages potato, tomato, eggplant, and bell pepper plants throughout North America. Scientists targeted the PSMB5 gene, which, when silenced, results in the death of the beetle. The pesticide was also tested on other beetles, and it was found that only agricultural pest beetles were affected by the pesticide. Not only this, but when the pesticide was tested on other insects, such as ladybugs and honey bees, no effect was observed. The fact that RNAi pesticides are able to target only specific pests, are cost-effective, and can be produced on a large scale reflects very positively on their prospects in the future of agriculture. This means that RNA pesticides are not only accessible but also a promising long-term solution to address issues with traditional pesticides.

Despite their prospective benefits, there are reasonable doubts that critics have regarding RNA pesticides. One of the most significant of these concerns is the fact that the pesticides are marketed as a spray. Critics are concerned that if these pesticides are used as sprays, it is possible that they may spread across the agroecosystem (ecosystems that support the production of food), making the sprays hard to contain. This is a potential issue because some genes may be unintentionally silenced, meaning non-target species may be affected as well. If untargeted species are affected, the unintentional collapse of an ecosystem is possible. It is also a concern that pests will develop a resistance to the RNA-based pesticides, as they have with traditional pesticides and solutions. This ultimately means that vital organisms required for ecosystems to survive will die while only invasive species and pests remain.

There are many uncertainties concerning the possibility of RNA pesticides, especially due to their incredibly recent development. However, recent research has shown that many previously held concerns regarding RNAi pesticides may not be as significant as once believed. In fact, studies have shown that RNAi pesticides can degrade in soil and water in less than 24 hours, meaning their environmental risks are relatively low compared to traditional chemical pesticides. As research continues, scientists may be able to identify additional genes shared across multiple pest species, allowing RNAi pesticides to become more efficient and effective. Further advancements could also make RNAi pesticide production cheaper, which would in turn increase accessibility for farmers. As further developments are made in the field, RNAi pesticides may eventually reduce the agricultural industry’s dependence on traditional chemical pesticides altogether. While more research is still needed to fully understand their long-term ecological impacts and drawbacks, it is clear that RNA pesticides possess the remarkable potential to change the agriculture industry forever.