Biopesticides: Nature's Pest Control
Bacillus thuringiensis: (Bt) was first registered
as a biopesticide in 1961. It is considered to be one
of the most successful biopesticides ever introduced.
It is highly specific in killing only a narrow range of
target pests by producing specific Cry and Cyt
toxins that do not kill beneficial pests or harm any
other neighboring organisms. Bt can be sprayed on
crops or Bt toxins can be incorporated into the host
plant’s genetic material. Bt primarily acts against
leaf and needle feeding caterpillars but strains have
been developed that act against flies and beetles.
It kills insects by producing toxins that paralyze
the digestive system of the pests, causing the
insect to stop eating, and leading to its death within
days. It is frequently sprayed on tomato, corn, alfalfa,
and cabbage crops. Bt crops are widespread, with 29 million acres of Bt protected crops cultivated in 1999. Bt has proven to be very effective, saving approximately $92 million on cotton crops alone in the U.S. Because of Bt’s record as a safe and effective biopesticide, it has acted as a paradigm for future biopesticides. Its success has led to greater crop yields in a safe manner, thus helping feed the growing world and acting as an example for future researchers to develop new biopesticides.
What Are some Examples of Biopesticides?
Baculoviruses: Baculoviruses are viruses that infect insects and other arthropods. They serve as excellent biopesticides because they only infect the target pest and do not harm plants, mammals, birds, fish or non target pests. However, this high specificity can be viewed as a weakness because it means that baculoviruses cannot be used to control a wide range of pests on one crop. To combat this, researchers are working to genetically engineer baculoviruses to kill a wide range of pests. Although the success of baculoviruses is undisputed, many farmers do not utilize them because they are relatively costly. This is because growing and isolating the virus usually involves growing live host insects, which is costly and labor intensive. The process of growing and isolating baculoviruses is detailed in the video in “impacts.” (Shown in the figure below.)
Beauveria bassiana: Beauveria bassiana is a fungus that is used to control a wide variety of insect pests. Various strains of it are found in the soil throughout the world. It grows on insects, secretes enzymes that weaken their outer shell, then enters the insect’s body and keep growing until the insect dies. It is used against a wide range of insects including weevils, aphids, borers, and whiteflies. There are no known risks to human health associated with Beauveria bassiana and it has been approved for all food uses. Beauveria bassiana is beneficial to the public as it provides a safe way to effectively manage pests.
Grasshoppers infected with Beauveria bassiana (Citation 29)
Bacillus thuringiensis (Citation 29)
How Bt works (Citation 27)
