Debugging the System: Understanding Pests, Pest Control, and Pesticides

February 3, 2020
Volume: 
3
Issue: 
1
Abstract / Synopsis: 

The reduction of crop loss from pest damage is often one of the most important goals in agriculture. The cannabis industry is now being called to task to account for the use of modern pesticides in their efforts. But, pest control in our modern times is a complex set of management strategies that include a variety of different tools in the arsenal. In this column, we examine the history of pest control and the strategies of modern pest management, including pesticides. By understanding the different approaches of pest management, the chemistry of pesticides, and life cycles of pests the cannabis industry can create better strategies not only to protect their products but also increase their output through better pest control systems. We examine some of the most common pesticides monitored within the cannabis industry and break down the function and chemistry of these agents in cannabis pest control.

Pest control is often considered to be a modern invention born of the chemical revolution at the turn of the last century. It is true that chemical pest controls are a relatively recent invention, but the practice of pest management is the product of evolution and biological relationships. The first acts of pest control were simple techniques such as fire to ward off dangerous predators or mud to cover the skin from biting insects. As agriculture came into existence, techniques increased from personal protection to include protection and expansion of crops. At its heart, the need to control pests is an expression of the control of species relationships.

Biology of Species Interactions

All the variations of interactions of species can be simplified into three basic scenarios. The first is mutualism in which the organisms involved actions benefit one another. An example in nature is the codependence of plants on nitrogen fixing bacteria in their roots. Each organism gains from the interaction. A human example could be some agricultural interactions such as with fruit trees where the humans gain food and the plant is cared for and seeds are spread.

The second type of interaction is commensalism. Commensalism is species interactions in which one species benefits and the other species neither is benefited nor harmed. Examples of these interactions include the relationship of epiphytes such as orchids which grow on trees. The trees do not benefit from the orchid but are not harmed. 

The third basic type of interaction is one of the most complex interactions—parasitism or predation. In these interactions, one species benefits but the other species is either harmed or killed. It is these interactions that started the need for pest management.

History of Pest Management

Prior to the industrial and chemical revolution of the 19th and 20th centuries there was a slow and ongoing battle with simple tools and chemicals. The early chemical weapons were elemental compounds of sulfur, heavy metals, and salts. Some of these compounds were in use up through the present day. Elemental sulfur was one of the earliest known pesticides used to deter lice and other pests. Heavy metal compounds were popular because of their toxicity. Arsenic compounds were highly effective against insects, bacteria, and fungi by binding with biologically important thiols and interrupting enzymatic processes, such as adenosine triphosphate (ATP) production. Mercury compounds also have an affinity for thiols and disrupt biological processes. Lead compounds act as a calcium analog and block calcium driven processes in the organism, such as heme synthesis.  These inorganic compounds lasted a long time and were not easily degraded. Unfortunately, they often leached into the ecosystem, wreaking havoc on local wildlife and posing a health threat to its human inhabitants.

Over the centuries science moved from religion and magic to practical study. The disciplines of chemistry and biology were founded, opening up studies into chemical compounds, reactions, and chemical synthesis. Pest control methods grew and benefited from this pursuit of knowledge. The 19th century saw the start of chemical synthesis and the rise of chemical pesticides. At first, chemicals were extracted and purified from their botanical sources. It was at this time that nicotine compounds were purified from tobacco, pyrethrums were extracted from flowers, and rotenone was isolated from roots. Compounds were blended and produced for the purpose of pest control. In 1814, an inorganic compound of copper (II) acetoarsenite called “Paris Green” was introduced as a pigment. By 1867, Paris Green was widely sold as an insecticide and rodenticide, which was produced up until the 1960s. 

During the Victoria era, traditional pest controls were investigated and their chemicals identified and isolated. As a result, all of the chemical compounds that were historically available in their botanical forms (for example, rotenone in roots and pyrethrums in chrysanthemums) were purified for commercial and home use, and elemental compounds were blended to create more efficient pesticides. The humble beginnings of simple, natural repellents and physical pest controls grew into chemical and agricultural industries seeking out new and improved methods.

References: 
  1. 1. JUS EPA, OCSPP. 2015. “Pesticides Industry Sales and Usage 2008 - 2012 Market Estimates.” Reports and Assessments. US EPA. October 29, 2015. https://www.epa.gov/pesticides/pesticides-industry-sales-and-usage-2008-2012-market-estimates.
  2. (“Modes of Action (MoA) Classification.” n.d. IRAC. Accessed December 10, 2019. https://www.irac-online.org/modes-of-action/.
  3. (Koul, Opender. 1996. “MODE OF ACTION OF AZADIRACHTIN.” In , 160–70.
  4. (Narahashi, T. 1971. “Mode of Action of Pyrethroids.” Bulletin of the World Health Organization 44 (1-2–3): 337–45.

About the Columnist

Patricia Atkins is a Senior Applications Scientist with SPEX CertiPrep and a member of both the AOAC and ASTM committees for cannabis.

How to Cite This Article

P. Atkins, Cannabis Science and Technology 3(1), 18-25 (2020).