Biological pest control

Biological control, often called biocontrol, is a method used to manage pests. Pests can be animals like insects and mites, or they can be plants like weeds. They can even be pathogens, which are organisms that cause disease in plants or animals. Instead of using chemicals, biocontrol uses other living organisms to control these pests. This process relies on natural mechanisms such as predation, where one animal eats another. It also uses parasitism, where one organism lives on or inside a host. Finally, it can use herbivory or competition to manage populations.

There are three primary strategies used in biological control. The first is classical biological control, also known as importation. This involves introducing a pest's natural enemy into a new area where it does not live naturally. The second strategy is augmentation. This means adding more natural enemies to an area to boost their numbers. Augmentation can be done through inoculative release, where small numbers are released to reproduce and prevent future outbreaks. It can also be done through inundative release, where huge numbers are released to fix an existing problem quickly.

The third strategy is conservation, also known as inoculative release. This involves taking measures to maintain and protect natural enemies that are already present in an environment. To be successful, a biological control agent needs specific traits. It must have the ability to colonize a new area effectively. It also needs temporal persistence, meaning it can survive even when the pest population is low. Finally, it should be an opportunistic forager. This allows the agent to find and exploit pest populations very rapidly.

Humans have used biological control for many centuries. One of the earliest reports comes from a Chinese text called "Nanfang Caomu Zhuang." This book was attributed to the botanist Ji Han, who lived during the Western Jin dynasty. It described how people in Jiaozhi used reddish-yellow ants to protect citrus fruits. These ants were known as huang gan ants. Modern biological control techniques began to emerge more clearly in the 1870s. During this time, entomologists in the United States began redistributing parasitoids to manage crop pests.

History shows several major successes in the field. In 1873, Charles V. Riley made the first international shipment of a control agent. He sent predatory mites to France to fight the grapevine phylloxera. In the late 1880s, the vedalia beetle was moved from Australia to California. This beetle helped control the cottony cushion scale, which was hurting the citrus industry. By the end of 1889, the scale population had already declined significantly.

Other impressive examples show how biocontrol can change landscapes. In Australia, the prickly pear cactus covered over 25 million hectares by 1920. To stop this, the cactus moth was introduced. Between 1926 and 1931, tens of millions of moth eggs were distributed. By 1932, most of the prickly pear had been destroyed. In Zimbabwe, the salvinia weevil helped control the giant salvinia weed. This program achieved 99 percent control of the weed over a two-year period.

Biological control is a vital part of integrated pest management (IPM) programs. However, scientists must be very careful when introducing new species. If a species is introduced without understanding the consequences, it can harm biodiversity. This happens if the agent attacks non-target species that were not meant to be part of the control. Today, new technology is even being used to help. For example, drones are now being introduced to assist with inundative releases of control agents.