Natural Pest Control in Organic Farm Systems

This is a concise summary of the practice of using biological agents like insects as pest control in organic farms. In brief and easy to understand terms, it introduces organic farming, discusses agents for biological control and some pest management strategies. This is a good read for someone who wants a simple overview of natural pest control practices without all the complex scientific terms.

Organic Farming

The goal of organic farming is to produce chemical-free healthy food. Farming practices rely on methods which combine knowledge of ecology and modern technology with traditional farming practices based on naturally occurring biological processes. In order to minimize the usage of synthetic pesticides, biological pest control is used. This is a method which uses other organisms to control insects, mites, weeds and plant diseases which rely on predation, parasitism, and herbivory or some other natural mechanisms, including an active human management role. Biological pest control creates no chemical runoff in waterways or soil pollution. It targets a narrow range of pests, sometimes even a single species and other beneficial insects. As a result, animals remain unharmed. Successfully established biological control species will maintain stable populations for generations without the need for additional investment by humans.

Biological Control Agents

Natural enemies of plant insect pests and diseases are known as biological control agents. They include predators, parasitoids, and pathogens. A predator is an organism that eats another organism (animal, plant, fungi or dead organic matter) while parasitoids are most of their life attached to or within a host organism which they have a relationship. It is similar to parasitism but they ultimately sterilize, kill or sometimes consume their hosts. Major Characteristics of Insect Parasitoids:

  • They are specialized in their choice of host
  • They are smaller than their host
  • Only the female searches for the host
  • Different parasitoid species can attack different life stages of host
  • Eggs or larvae are usually laid in, on, or near the host
  • Immatures remain on or in the host; adults are free-living, mobile, and may be predaceous
  • Immatures almost always kill the host.

Pathogens are microorganisms, and infectious agents such as viruses, bacteria, prion or fungi which fight against other plant diseases. They prevent pathogens from colonizing crops. Biological control agents of weeds are seed predators, herbivores, and plant pathogens. Pest management in organic farming often combines biological control agents, especially in cases of massive and severe infections of invasive pests.

Pest Management Strategies

There are three basic biological pest control strategies: importation (classical biological control), augmentation and conservation.

Importation – classical biological pest management in organic farming which introduces pest’s natural enemies to the locations where they do not occur naturally. This strategy requires biological control agents with the colonizing ability and temporal persistence in order to maintain its population and rapidly exploit a pest population.

Augmentation – involves the supplemental release of natural enemies, boosting the naturally occurring population. It can include a small or large release of the control agents, depending on the pest management needs. To keep pests at a low level, to prevent a severe attack, small release controlling agents are sufficient. However, for rapid reduction (correction) of the damaging pest population, a large number of control agents is needed. Augmentation can be effective, but is not guaranteed to work, and it relies on the understanding of the situation.

Conservation – this involves the conservation of existing natural enemies in the environment already adapted to the habitat and the target pest. Conservation pest management is usually simple and cost-effective. To favor natural enemies, cropping systems can be modified to provide a suitable habitat. Shelterbelt, hedgerow or beetle banks provide shelter where beneficial insects can live and reproduce. This enables farmers to ensure the survival of populations.

This post is sourced from an article originally written by Tanja Folnovic, an agronomy expert, for the Agrivi blog, which can be found here.



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