Ep 3: Pesticides

According to Mohamood et al., pesticides are "...toxic chemical substances or biological agents that are intentionally released into the environment" (2016). These toxic chemicals can have a disastrous impact on both human health and environmental health. Pesticide use has been around for hundreds of years and have evolved over time to first be made from natural compounds and now typically made from synthetic compounds. There are six major types of pesticides that are in use, which include:

• Organophosphates - Neurotoxins used on pests

• Carbamates - Similar to organophosphates, but less toxic

• Organochlorine - POPs that have the ability to bioaccumulate in humans and wildlife

• Pyrethroid - Synthetic version of pyrethrin from the Chrysanthemum flower which is toxic on the nervous system

• Biopesticides - A variety of pesticides/methods that are biologically derived

• Herbicides - Pesticide widely used in gardening

(Frumkin et al., 2016; Mahmood et al., 2016)

Photos: legallegacy.wordpress.com/2019/11/01/november-1-1986-sandoz-chemical-spill/

There are several key aspects of IPM that will be discussed, but a key factor is to ensure that combination of IPM strategies are used (Stenberg, 2017; Barzman et al., 2015). Overall, the goals of IPM are long-term sustainability as a pest control method and a decreased negative impact of pesticides on human and enviornmental health (Barzman et al., 2015).

Long-term sustainability is achieved if IPM is implemented on a continuum. On this continuum, an agricultural company may gradually transition from no IPM use to high IPM use. Additionally, this allows the company to asses whether there are changes among pest populations, threats, or policies. The key aspects of IPM include pest control (mechanical, physical, biological, selective pesticide use), structural maintenance, monitoring, control measures, and consumer education (Frumkin et al., 2016; Barzman et al., 2015).

Ultimately, IPM is working to reduce the impact of particular pest rather than total eradication. Many countries have already begun working towards the eight key IPM principals (Barzman et al., 2015):

• Prevention and Suppression

• Monitoring

• Decision Based on Monitoring and Threshold

• Non-Chemical Methods

• Pesticide Selection

• Reduced Pesticide Use

• Anti-Resistance Strategies

• Evaluation

Microbial Pesticides and Plant Incorporated Protectants (PIPs)

Microorganisms are used as an active agent. They are genetically added to the plant and when a pest eats the plant it is then toxic to them (Frumkin et al., 2016).

Example: Bacillus thuringiensis - See video below

(Frumkin et al., 2016)

Biochemical Pesticides

Biochemical pesticides are nontoxic methods for controlling pests. While there are many types, a prime example of this type of pesticide is insect sex pheromones.

• Pheromones are used to disrupt matting patterns for insects through two different methods.

Method 1: An excessive amount of sex pheromone is released into the environment which causes males to be unable to locate females. Because they are unable to locate females, reproduction does not occur.

Method 2: Use of pheromone traps to trap a large number of genetically male/female insects. This would mean that they are unable to reproduce at previous levels because there is less of one sex.

(Stenbern, 2017; Frumkin et al., 2016)

Botanical Pesticides

Botanical pesticides are pesticides that are derived from plants and typically display low mammalian toxicity. Because they are naturally derived, these forms of pesticides degrade more quickly and release less toxins as they decompose meaning they will have less of an impact on the environment (Landscape IPM). Commonly used botanical pesticides and the sources they are derived from include:

• Pyrethrins - derived from pyrethrum flower dust (chrysanthemum)

• Rotenone - derived from legumes and cube root to form a dust

• Sabadilla - derived from the seeds on a tropical lily plant

• Ryania - derived from a shrub commonly found in South America

• Nicotine - derived from the tobacco plant

• d-Limonene and Linalool - derived from citrus oils

• Neem - derived from the Neem tree in which an oil is created that is applied to plants to suffocate insects

(Frumkin et al., 2016; Landscape IPM)

Intrinsic Heritable Plant Resistance

This is the idea that plants develop traits that create direct or indirect defenses against pests and pathogens.

Direct Defenses: "...directly defy attackers, making the plant less detectable, attractive, edible, or susceptible to infection"

Indirect Defenses: "...attract and reward the natural enemies of pests, thereby engaging them as ‘bodyguards’"

Unfortunately, as crops continue to become more domesticated, we are seeing a decrease in the differences in defense traits. Initially this was due to the increase in chemical pesticide use meaning resistant traits were not longer required to allow crops to flourish.

(Stenbern, 2017)

Plant Vaccination

This is the idea that plants are primed with direct and indirect defenses to protect themselves. The more they are attacked by a pest, the more they are primed. Because of this method of priming, there is a reduction in metabolic cost.

As an example by Sternbern (2017):

"...tomato plants grown from jasm-onate and b-aminobutyric acid-treated seeds reportedly have stronger induced defenses than controls against both arthropod pests and pathogenic fungi."

(Stenbern, 2017)

Crop Diversity and Rotation

Crop Diversity - We need a variety of the same species if a monoculture is being used. If there are multiple different varieties of the same plant, the pest is less likely to be able to destroy the plant in the event there is an outbreak.

Crop Rotation - avoiding use of the same crop multiple cultivation cycles in a row. A clear example is in Europe with the Western Corn Rootworm. This pests life cycle lasts through two cultivation cycles. If we were to rotate to an entirely different crop after one cultivaiton cycle this would break the cycle in development of the Rootworm and decrease the overall population.

(Barzman et al., 2015; Stenbern, 2017)

From an environmental justice perspective, transitioning to IPM is not only beneficial to our environment, but also to human health. Agricultural workers, who are regularly exposed to chemical pesticides, are at an increased risk for cancer, Parkinson's disease, Alzheimer's disease, reproductive disorders, and birth defects (Kaur & Kaur, 2018). In the case of pesticide use, humans are considered non-target species after exposure and often times appropriate protective personal equipment such as gloves or respirators are not worn. Overtime, pesticides will bioaccumulate in the body leading to a disruption in a number of body systems including (Kaur & Kaur, 2018):

• Nervous System

• Reproductive System

• Respiratory System

• Immune System

• Cardiovascular System

While regular exposure to pesticides can be detrimental to the health of agricultural workers, transitioning to IPM focused strategies can resolve many of those issues. With the use of IPM strategies, workers are no longer exposed to the same degree of harmful toxicants.

Per the USDA, the Office of Pest Management Policy allows for the communication between federal agencies to promote the development of pest management strategies. Under this policy, federal agencies are required to encourage IPM practices through regulation and activities. Chaired by this policy is the National Road Map for Integrated Pest Management. This roadmap plays a key role in providing guidance on effective, economical, and safe IPM strategies. There are three potential approaches that may be used to strength IPM that are discussed within this roadmap (Integrated Pest Management, n.d.):

• "Improve economic and social analyses of adopting and implementing IPM practices;

• Reduce potential human health and safety risks from pest and related pest management strategies; and

• Minimize adverse environmental effects from pests and related management practices."

There is currently a Swiss agricultural policy that was created to subsidize IPM. According to Barzman et al., this policy has lead to 98% of Swiss agriculture contributing to ecological services and 88% of that falls under IPM (2015).

Additionally, as discussed, there are a number of monitoring systems in place throughout Europe.

Barzman, M., Bàrberi, P., Birch, A. N., Boonekamp, P., Dachbrodt-Saaydeh, S., Graf, B., Hommel, B., Jensen, J. E., Kiss, J., Kudsk, P., Lamichhane, J. R., Messéan, A., Moonen, A.-C., Ratnadass, A., Ricci, P., Sarah, J.-L., & Sattin, M. (2015). Eight Principles of Integrated Pest Management. Agronomy for Sustainable Development, 35(4), 1199–1215. https://doi.org/10.1007/s13593-015-0327-9

Bertomeu-Sánchez, J. R. (2019). Introduction. pesticides: Past and present. HoST - Journal of History of Science and Technology, 13(1), 1–27. https://doi.org/10.2478/host-2019-0001

Freeman, B.C. and Beattie, G.A. 2008. An Overview of Plant Defenses against Pathogens and Herbivores. The Plant Health Instructor. DOI: 10.1094/PHI-I-2008-0226-01

Frumkin, H., Mark Robson, Hamilton, G., Siriwong, W., & Maldonado Pérez, H. (2016). Pest Control and Pesticides . In Environmental health: From global to local (3rd Edition, pp. 483–489). essay, Jossey-Bass. A Wiley Brand.

Frumkin, H., Mark Robson, Hamilton, G., Siriwong, W., & Maldonado Pérez, H. (2016). Pest Control and Pesticides . In Environmental health: From global to local (3rd Edition, pp. 490). essay, Jossey-Bass. A Wiley Brand.

Images . StockSnap. (n.d.). Retrieved November 15, 2021, from https://stocksnap.io/.

Integrated Pest Management. USDA. (n.d.). Retrieved November 15, 2021, from https://www.usda.gov/oce/pest/integrated-pest-management.

Kaur, K., & Kaur, R. (2018). Occupational Pesticide Exposure, Impaired DNA Repair, and Diseases. Indian journal of occupational and environmental medicine, 22(2), 74–81. https://doi.org/10.4103/ijoem.IJOEM_45_18

Landscape IPM. Botanical Insecticides " Landscape IPM. (n.d.). Retrieved November 25, 2021, from https://landscapeipm.tamu.edu/types-of-pest-control/chemical-control/organic/botanical/.

Mahmood, I., Imadi, S. R., Shazadi, K., Gul, A., & Hakeem, K. R. (2016). Effects of pesticides on environment. Plant, Soil and Microbes, 253–269. https://doi.org/10.1007/978-3-319-27455-3_13

NPIC at OSU. (2015, February 16). Bacillus thuringiensis (bt). YouTube. Retrieved November 25, 2021, from https://www.youtube.com/watch?v=3aLj1WmzL98.

Pearse, I.S., LoPresti, E., Schaeffer, R.N., Wetzel, W.C., Mooney, K.A., Ali, J.G., Ode, P.J., Eubanks, M.D., Bronstein, J.L. and Weber, M.G. (2020), Generalising indirect defence and resistance of plants. Ecol Lett, 23: 1137-1152. https://doi.org/10.1111/ele.13512

Stenberg, J. A. (2017). A conceptual framework for Integrated Pest Management. Trends in Plant Science, 22(9), 759–769. https://doi.org/10.1016/j.tplants.2017.06.010

USDA. (n.d.). History of the Federal Integrated Pest Management Coordinating Committee. USDA. Retrieved November 15, 2021, from https://www.usda.gov/sites/default/files/documents/20201110-FIPMCC-History.pdf.