The wasp Aleiodes indiscretus is used to control gypsy moth.  They can be reared to large numbers and released in pest-infested areas
Image: Public Domain.

Biocontrol, short for biological control, uses living organisms to reduce and control populations of pest organisms. In classical biological control the pest organisms can be an invasive animal or plant species with no or few natural enemies in its new location, and the biocontrol agent can be a natural enemy of the pest species imported from the pest’s home range.

Depending on the nature of the pest species, control agents might be pathogens, insects, grazing or predatory animals. There also are other biological control strategies that do not involve importation of natural enemies and focus on augmenting or promoting populations of native species that can control the pest.

For more information:

Biocontrol in Australia: Can a carp herpesvirus (CyHV-3) deliver safe and effective ecological restoration?

Biological control of pests and a social model of animal welfare

Biocontrol: what is it?

North American Invasive Species Management Association (NAISMA) is a good place to explore this topic further.

This is a form of biological control in which genetic variants or genetically modified forms of the target species serve as controlling agents in some way, so that the threat posed by the target species is reduced or eliminated. For example, the target might be an agricultural pest species or a vector species that transmits human, animal, or plant diseases. Genetic biocontrol has the advantage of expanding the scope of target pest species beyond those for which classical biocontrol agents are available.

For more information:

See also:

The promise and challenges of genetic biocontrol for malaria elimination https://www.mdpi.com/2414-6366/8/4/201

Most forms of genetic biocontrol have a similar goal as classical biocontrol: to reduce the population of a problem-causing organism, generally by inhibiting its ability to reproduce. These are termed “population suppression strategies.” Some forms of genetic biocontrol are now being developed that aim to modify the pest organism in such a way that its ability to cause the problem is reduced. This might be accomplished, for example, by inhibiting its ability to transmit a disease-causing pathogen. These are termed “population replacement” or “population modification strategies.”

Various types of genetic biocontrol have been proposed for use in public health, agriculture, and conservation. For public health, they can contribute to preventing transmission of vector-borne infectious diseases. For agriculture, they can help to reduce crop loss caused by insect pests. For conservation, they have been proposed as a method for controlling invasive species that cause loss of biodiversity.

For more information:

https://www.youtube.com/playlist?list=PLbopRNGowKJ9dtCMDZ9_LQRHyw084vgIP
https://www.geneticbiocontrol.org/

There are a number of conditions in which genetic biocontrol approaches can be useful. For example, when other control strategies are or are becoming ineffective, as is the case with development of pesticide resistance in insects or weeds. Like classical biocontrol, genetic biocontrol strategies can be a powerful adjunct to pesticide-based strategies and reduce our dependence upon them. Genetic biocontrol can also be useful in situations where conventional chemical approaches cannot fully address the problem because it is so difficult or expensive to deliver these approaches in areas where pests breed or cause damage. Living biocontrol organisms have the advantage of being biologically inclined to seek out the pest they are intended to control, simplifying delivery. Additionally, genetic biocontrol may be considered by some as more environmentally friendly or humane than chemical approaches.

This is a matter of definition. If one defines genetic modification as a change in the genetic material through the use of modern biotechnology (genetic engineering), then the answer is no. Genetic biocontrol does not always use organisms that are genetically modified. The genetic make-up of an organism can be altered in several ways other than via molecular biology. Traditionally, this has been accomplished over time through selective breeding. Genetic changes also can be introduced using irradiation, as is the case for the classical Sterile Insect Technique (SIT), or by infection of the organism with a new microbe, such as a virus or bacterium.

There are variants of SIT and other biocontrol strategies that involve the release of insects that have been modified in the laboratory (genetically engineered) to effect a functional change. Genetic changes introduced using molecular biology technologies are expected to be more controllable and predictable than the random chromosomal damage caused by irradiation.

Fore more information:

https://royalsociety.org/topics-policy/projects/gm-plants/how-does-gm-differ-from-conventional-plant-breeding/

The most well developed and widely used genetic biocontrol is the Sterile Insect Technique (SIT). This is an insect control strategy devised in the middle of the 20th century, in which a target species of insect is mass-reared to large numbers and then sterilized using ionizing radiation, which causes a multitude of random chromosomal mutations that lead to infertility. Large numbers of irradiated insects are released into wild populations of the same target species. Preferably only sterilized males are released and when they find and mate with a fertile wild female, the female will produce no viable offspring although her drive to find a mate and reproduce has been satisfied. Regular repeated releases of sterile males over time can result in a reduction of the target population and in some cases its local elimination.

Another example of genetic biocontrol involves the use of a hybrid incompatibility phenomenon wherein mating between two strains of a species results in a reduced number of offspring as compared to mating between individuals of the same strain.

For more information:

https://www.iaea.org/sites/default/files/19/02/controlling-insect-pests-with-the-sterile-insect-technique.pdf
https://www.youtube.com/playlist?list=PLbopRNGowKJ9dtCMDZ9_LQRHyw084vgIP

The genetic biocontrol known as the Sterile Insect Technique, based on irradiation, has been used safely across the globe for decades to control agricultural pests. For example, in Central America sterile New World Screwworm flies are released to prevent the northern migration of these important livestock pests from South America into Mexico, Central America, and the Southern US.  Mass reared radiation-sterilized male Mediterranean Fruit Flies are or have been used to control this major pest of citrus and other fruits in countries including Argentina, Mexico, Portugal, Dominican Republic, Guatemala, Spain, South Africa, and the USA.

Genetic engineering also is being applied to control of agricultural pests such as Mediterranean Fruit Fly and Fall Armyworm. Oxitec’s Friendly^TM technology for Fall Armyworm has been approved by the Brazilian biosafety agency.

For more information:

https://www.iaea.org/topics/sterile-insect-technique;

https://www.taylorfrancis.com/books/oa-edit/10.1201/9781003169239/area-wide-integrated-pest-management-jorge-hendrichs-rui-pereira-marc-vreysen; https://www.oxitec.com/en/food-sustainability

Genetically modified mosquitoes are developed using genetic engineering. Gene drive-modified mosquitoes are a type of genetically modified-mosquitoes. In both cases, mosquitoes of the targeted species are modified to exhibit one or more different traits from wild type (non-modified) mosquitoes of the same species. An example of a desirable new trait would be a decreased ability of the modified mosquitoes to transmit diseases such as malaria or dengue. Modifications might involve altering the sequence of existing genes, disabling or excising of existing genes, or introducing new genes or other genetic elements within the mosquito genome.

Several genetic modification approaches are being explored, from those that will have no lasting effect on the targeted vector population after release to those that are intended to introduce a more persistent change. When not coupled to a gene drive, a gene (including any introduced genetic modification) is typically transmitted to the progeny from mating of modified with wild type mosquitoes according to the standard (Mendelian) pattern of inheritance, where each gene has a 50% chance of being passed from the parent to the next generation. If the gene or genetic modification is associated with a fitness cost (reduced competitive ability), the related trait is expected to disappear from the population over time. If the fitness cost is severe, the introduced gene(s) can disappear rapidly; this would be the case, for example, if the modification caused reduced fertility in those mosquitoes that carried it.

When coupled with a gene drive, the genetic modification is inherited preferentially. The related new trait will eventually become dominant in the population because more than 50% (sometimes almost 100%) of the progeny from matings between gene drive-modified mosquitoes and their wild-type counterparts inherit the modification.

For more information: https://www.geneconvenevi.org/gene-drive-defined/