Pest Control Methods (College Board AP® Environmental Science): Study Guide

Pesticide resistance through artificial selection

What is pest control?

• Pest control refers to methods used to manage or eliminate organisms that harm crops, livestock, or human health

• Common pest control strategies involve the use of chemicals

Chemical control

• Chemical control refers to the use of pesticides, herbicides, fungicides, rodenticides, and insecticides to kill or deter pests

  • Pesticides are chemicals used to kill or deter insects (e.g., insecticides)

  • Herbicides are chemicals that target weeds

  • Fungicides are used to control fungal infections in crops

  • Rodenticides are used to eliminate rodents

  • Insecticides specifically target insect pests

Pest control benefits

• Reduces crop damage by preventing pests from feeding on plants

• Increases agricultural productivity by improving crop yields

• Protects food supplies and prevents the spread of diseases caused by pests

What is pesticide resistance?

• Pesticide resistance occurs when pest populations evolve to be resistant (i.e. to withstand) chemicals used to control them

• This happens through artificial selection, where repeated exposure to pesticides selects for resistant individuals

• Resistant pests survive, reproduce, and pass on resistance genes, making pesticides less effective over time

How artificial selection leads to resistance

1. Initial pesticide application: A pesticide is applied to control a pest population

2. Survival of resistant individuals: Some pests naturally have genetic mutations that make them resistant

3. Reproduction of resistant pests: These resistant individuals survive and pass their traits (genes) to their offspring

4. Population shifts: Over time, more pests in the population inherit resistance, reducing the pesticide's effectiveness

Consequences of pesticide resistance

• Increased crop damage: Resistant pests continue feeding on crops, reducing agricultural yields

• Higher pesticide use: Farmers may apply stronger or more frequent pesticide treatments, increasing costs and environmental harm

• Harm to non-target organisms: Overuse of pesticides can kill beneficial insects, such as pollinators (e.g., bees)

• Contamination of ecosystems: Pesticide runoff can pollute soil, water, and air

Advantages & disadvantages of genetically engineered crops

What are genetically engineered crops?

• Genetically engineered (GE) crops are plants whose DNA has been modified using biotechnology to introduce desirable traits

• Common modifications include pest resistance, herbicide tolerance, drought tolerance, and increased nutritional content

• These crops are widely used in modern agriculture to:

  • improve food production

  • reduce losses due to environmental factors

Advantages of genetically engineered crops

Increased pest and disease resistance

• GE crops can be modified to resist pests and diseases

  • This reduces the need for chemical pesticides

• Example: Corn has been genetically modified with a gene for the Bt toxin, which is taken from the bacterium Bacillus thuringiensis

  • Bt corn produces its own insecticide, reducing crop losses from insect damage

Higher crop yields

• Improved resistance to pests, diseases, and environmental stressors leads to higher food production

• Helps address food security issues, particularly in regions with high population growth

Reduced pesticide and herbicide use

• Pest-resistant crops require fewer chemical applications

  • This lowers production costs and reduces environmental contamination

• Herbicide-tolerant crops allow for targeted weed control, improving efficiency

Drought and climate resilience

• Some GE crops are modified to tolerate drought, extreme temperatures, and poor soil conditions

• Example: Drought-resistant maize helps farmers in arid regions maintain productivity

Enhanced nutritional content

• Some GE crops are developed to contain higher levels of essential nutrients

• Example: Golden Rice, which is fortified with Vitamin A to combat malnutrition

Disadvantages of genetically engineered crops

Loss of genetic diversity

• Large-scale planting of GE crops reduces genetic variation

  • This makes crops more vulnerable to new pests and diseases

• Lack of diversity can lead to greater susceptibility to crop failures

Potential environmental risks

• Crossbreeding with wild plants can introduce GE traits into natural ecosystems, potentially disrupting native species

• Some herbicide-tolerant crops encourage higher herbicide use, leading to resistant weeds ("superweeds")

Ethical and economic concerns

• Patented GE seeds are often owned by large corporations, limiting farmers' rights to save and replant seeds

• GE seeds can be expensive, making them inaccessible to small-scale or subsistence farmers

Uncertainty over long-term effects

• While studies show GE crops are generally safe, concerns remain about long-term health impacts and their effects on biodiversity