Pest Invasions

A pest invasion is the occurrence of a pest species in a location where its number and impact is at an intolerable level. A pest may be any harmful living organism, but the term usually has an agricultural reference. Pest invasions may result from a combination of ecological and climatic factors, such as weather patterns, monocropping, new species introduction, or migration patterns.

Relief agencies can reduce the risk of disasters from pest invasions by assisting in community mobilization, technical training, provision of essential materials, and [Page 472]advocating for government policies toward mitigation and response measures.

The Mediterranean fruit fly (left) is one of the world's most destructive fruit pests; eradication is difficult and expensive. Fire ants (right) are dangerous pests throughout the southeastern United States. Both require the latest pest management technologies

A pest refers to an organism that is either directly or indirectly harmful; unwanted; or injurious to humans, animals, crops, or possessions. Pests may broadly include microbes, invasive plants, insects, rodents, and large animals. Some pests will vector (transmit) diseases, such as the parasitic guinea worm; mosquitoes, which vector malaria; or rats, which carried fleas that transmitted the dreaded Bubonic Plague, known literally as pestis in Latin. However, the term pest is most often used to refer to agricultural damage through destructive impact on crops and woodlands, or parasites that affect livestock. The Food and Agricultural Organization (FAO) estimates that 40 percent of world's food supply is lost due to pests, in spite of numerous control measures.

Pest Infestation and Invasion

An agricultural pest infestation occurs when one or more pest species exists at an unmanageable or destructive level. The introduction of the pest is likely to cause environmental, economic, or human health harm. Critical pests are those that lead to loss of crop quantity or quality, resulting in a negative effect on household livelihoods and communities by either decreasing food available to markets, or reducing foodstocks for subsistence living. The pest invasion may be either a sudden rise or a slow increase in population.

Generally, pest invasions are predictable because they cluster in geographic areas. However, rather than a quick-onset natural disaster such as an earthquake, avalanche, or fire, a pest invasion is usually slow-onset and may go undetected. Whether from a sudden rise or a slow spread, the increase in pest population often has a cascading effect to contribute to another hazard, such as drought, famine, desertification, or deforestation. These disasters can be devastating, especially in underdeveloped countries or regions where the level of food security is already compromised by substandard agricultural output. Agricultural pests know no borders, and may migrate or spread across countries to cause catastrophic, sub-continental losses.

Pest invasions such as insects or invasive plant are usually the result of a combination of ecological and climatic factors. Seasonal temperature is often the most important factor. Climate change could upset the balance between plant or insect pests and the natural enemies that control their numbers, resulting in outbreaks of increased frequency or increased severity. The migration of a pest to a different area with equally or more favorable conditions may allow species to escape control and increase in numbers. Farming practices can unintentionally introduce pests as well. Modern monocropping methods result in greater vulnerability to pests due to less natural resistance and fewer natural enemies. Some pest problems arise from plants, insects, [Page 473]or rodents that are introduced into new biological communities by humans with good intentions. In addition, for flying insects such as locusts, the prevailing winds and weather patterns help determine where they will fly, survive, and impact the environment.

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