8.3 Biological pest control methods

Biological pest control methods harness nature's own defense mechanisms to manage pests. These strategies use living organisms and their relationships to keep pest populations in check, offering a sustainable alternative to chemical pesticides.

From beneficial insects to microscopic nematodes, this approach taps into the power of predator-prey dynamics and microbial controls. By understanding and leveraging these natural systems, we can create healthier, more balanced ecosystems in our gardens and farms.

Beneficial Organisms

Natural Enemies and Predator-Prey Relationships

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• Natural enemies are organisms that prey on or parasitize pests, helping to control their populations
  • Includes predators (ladybugs), parasitoids (wasps), and pathogens (fungi)
• Predator-prey relationships involve one organism (predator) hunting and consuming another (prey)
  • Helps maintain balance in ecosystems by preventing any one species from becoming too abundant (aphids and ladybugs)
• Encouraging natural enemies through habitat creation and avoiding broad-spectrum pesticides promotes biological control
  • Planting diverse vegetation provides shelter and alternative food sources for beneficial insects (flower strips in agricultural fields)

Nematodes as Biological Control Agents

• Nematodes are microscopic roundworms that can parasitize insects and other pests
  • Entomopathogenic nematodes infect and kill specific insect hosts (Steinernema feltiae targets fungus gnat larvae)
• Nematodes are applied to soil or foliage where they seek out and enter pest hosts
  • Once inside, they release symbiotic bacteria that kill the host and provide food for nematode reproduction
• Nematodes are safe for plants and animals, making them an effective, targeted biological control option
  • Commercially available for controlling various soil-dwelling and boring insect pests (root weevils, stem borers)

Microbial Controls

Microbial Pesticides

• Microbial pesticides contain microorganisms or their byproducts that can control pests
  • Includes bacteria (Bacillus thuringiensis), fungi (Beauveria bassiana), and viruses (baculoviruses)
• These pesticides are highly specific to certain pests and are safe for beneficial organisms and the environment
  • Bacillus thuringiensis (Bt) produces proteins toxic to caterpillars but harmless to other insects and animals
• Microbial pesticides are applied as sprays or granules and can be used in organic farming
  • Bt corn is genetically engineered to produce Bt proteins, protecting against European corn borer

Conservation and Augmentation Strategies

• Conservation biological control involves modifying the environment to support existing natural enemy populations
  • Reducing pesticide use, providing overwintering sites (beetle banks), and planting nectar sources (alyssum)
• Augmentation involves releasing additional natural enemies to supplement existing populations
  • Inoculative releases introduce small numbers of natural enemies early in the season to allow population buildup (green lacewings in greenhouses)
  • Inundative releases involve large numbers of natural enemies for immediate, short-term control (Trichogramma wasps against codling moth in orchards)

Traps and Diversions

Pheromone Traps and Mating Disruption

• Pheromone traps use synthetic insect pheromones to attract and capture pests
  • Sex pheromones lure males into traps, monitoring population levels and reducing mating (codling moth in apple orchards)
• Mating disruption involves releasing large amounts of synthetic pheromones to confuse males and prevent them from locating females
  • Disrupts mating and reduces pest populations over time (grapevine moths in vineyards)

Trap Crops and Banker Plants

• Trap crops are plants that are more attractive to pests than the main crop, luring them away from the primary planting
  • Planting collards around cabbage fields attracts diamondback moth, reducing damage to cabbage
• Banker plants provide habitat and alternative prey for natural enemies, helping to maintain their populations
  • Planting rye grass in greenhouses harbors aphids that serve as food for predatory wasps, which also control pest aphids on the main crop (sweet peppers)
• These strategies manipulate pest behavior and enhance natural enemy populations for effective biological control