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09.03 IPM: Chemical Control

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Bugs 101: Insect-Human Interactions

University of Alberta

4.9 (131 ratings) | 7.3K Students Enrolled

Of all the animals on earth, which are the strongest for their size? What about the fastest? Who were the first animals to evolve flight? Insects take all of these titles and more! As the most abundant animals on the planet, insects and other arthropods affect our lives in so many ways. From beneficial interactions like pollination and biological pest control, to the transmission of life threatening diseases; this course will teach you about the big ways that these little arthropods impact our lives. In Bugs 101: Insect-Human Interactions, you will be plunged into the diverse (and sometimes alien) world of arthropods to learn how they work, what they do, and how insects and humans interact every day. After completing this course, you will be able to: Describe the evolutionary relationships between insects and their arthropod relatives Inventory major groups of insects and their diversity Demonstrate evolutionary adaptations that make insects successful Discuss insect biology and human-insect interactions Evaluate positive and negative interactions between insects and humans Propose practical and symbolic roles insects play in human societies

Skills You'll Learn

Biology, Entomology, Science, Ecology

Reviews

4.9 (131 ratings)

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LB

Sep 18, 2019

Fantastic course full of interesting and useful information that is presented in a structured and clear way. A big thank you to the course presenters and plethora of guest experts.

JK

Aug 19, 2019

I learned so much from this class. Most importantly, I appreciated the faculty that would answer my questions in the forum, it made me feel more connected to the course.

From the lesson

Module 09: Sustainable Human-Insect Interactions: IPM

Integrated pest management (IPM) is a pillar of modern crop production, and the preservation of ecosystem function/health. A variety of chemical pesticides can be a part of IPM programs. The different insecticides available to manage insect pests vary in many regards, such as their modes of action and application. The use of these pesticides is not without risks, however, and these must be considered if we want to reap the benefits these chemicals can provide.

09.03 IPM: Chemical Control5:36

Taught By

Dr. Maya Evenden
Professor of Entomology

Transcript

If monitoring shows pest population densities are above an established action threshold, it becomes necessary to implement control measures to suppress their numbers. Synthetic insecticides have been an important tool for pest management since their widespread introduction following World War II. Today, they are still an important component of integrated pest management systems. A pesticide is a broad term that applies to chemicals that kill organisms considered to be pests. Not all pests are insects, and not all pesticides are insecticides. Insecticides are chemicals that are lethal to insects, which are applied to kill insect pests. Insecticide chemicals are an important component of integrated pest management in most managed systems, but must be carefully applied to avoid harming non-target organisms. The economic importance of pesticides to agriculture is illustrated by the amount of money spent on them each year. For example, world pesticide expenditures in agriculture totaled nearly $56 billion in 2012. This total includes money spent on all types of pesticides, including insecticides, herbicides, and fungicides. Choosing the right pesticide requires the consideration of several criteria. Safety for the user, target species specificity, effectiveness, persistent in the environment, speed of action, and cost. The class of a compound is also an important consideration as repeated use of synthetic pesticides from the same class of chemicals can lead to the development of resistance in the pest population. We will discuss different types and classes of pesticides in the next lesson. Insecticides can affect an insect system in various ways depending on the modes of application. These can be divided into three basic categories; stomach poisons, contact poisons, and fumigants. Stomach poisons are chemicals that impact the insect through consumption of the compound. A common example of a stomach poison is the Delta Endotoxin produced by the bacteria Bacillus thuringiensis or Bt. When crystals of these toxins are ingested, they pass through the peritrophic membrane and create open pores in the midgut. This damages and paralyzes the digestive system causing death by starvation and infection. Contact poisons on the other hand are insecticides that enter an insect's system through the body wall. They are absorbed by the insect upon contact when the insect crawls over a treated surface. This type of insecticide is applied to the surfaces of plants. So it is only effective against insects that feed from the outside and less so for those that feed from within the plant. One such insecticide is malathion, which impacts the insects nervous system at the synapse between nerve cells. Another way that insects can be exposed to insecticides is as a vapor in the treated environment. Insecticides that are gaseous above five degrees celsius are known as fumigants. Fumigants enter the insect body through spiracles that open into the tracheal system. Once in the trachea, fumigants are absorbed into the body tissues. Fumigants are generally effective in that they kill all life stages of some insects including the eggs. Due to the aerosolized nature of the poisons, fumigants are usually used in enclosed environments where the pesticide can be contained, like in a greenhouse. They can also be used to treat stored products. Although, preventive methods such as temperature treatments and prespraying storage units are usually employed before fumigation is considered. It is important to apply fumigants in enclosed environments because they can be toxic to humans and should be used with caution. The use of many fumigants such as methyl bromide has been restricted due to environmental concerns. While insecticides can be divided into three large categories based on their modes of application, stomach, contact, and fumigant, we can also divide them into classes based on their source or chemical structure. In the next video, we will explore the many different types of insecticides commonly used for pest management.

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