**2. Genetically engineered plant insecticides**

The technology of 'genetically engineered insecticides' is based on the development of plants or viruses genetically engineered to produce insect-selective toxins. This involves transferring naturally occurring poison-coding genes from microorganisms into crops. Such insecticides may be referred to as biopesticides or biological pesticides. The latter are based on pathogenic microorganisms specific to a target pest and offer an ecologically sound and effective solution to pest problems. The most commonly used biopesticides are living organ‐ isms, which are pathogenic for the pest of interest. Biopesticides fall into three major catego‐ ries namely: biofungicides (*Trichoderma*), bioherbicides (*Phytophthora*) and bioinsecticides (*Bacillus thuringiensis*). Biopesticides contain a microorganism such as bacterium, fungus, vi‐ rus, protozoa or alga, as the active ingredient.

The most widely known microbial insecticides are based on the bacterium *Bacillus thurin‐ giensis* (Bt.), which is incorporated into plants to produce genetically modified (GM) crops or genetically modified organisms (GMO). Bt is a soil dwelling Gram-positive bacterium, dis‐ covered in 1901 by a Japanese biologist, Shigetane Ishiwatari. Later it was rediscovered in Germany by Ernst Berliner in flour moth caterpillars. The spores and crystalline insecticidal proteins produced by Bt have been used for insect control since 1920s (Lemaux, 2008). ). In 1995 potato plants, incorporating Bt, were first introduced in the USA (Romeis et al, 2008) and by 1996 Bt maize, potato and cotton were grown. GMO technology is claimed to allevi‐ ate poverty by ensuring high incomes from insect prone cash crops such as cotton, maize or rice. Some Bt-based insecticides are often applied as liquid sprays on crops, where the insec‐ ticide is expected to be ingested by pests for it to be effective. A Bt strain, *Bacillus thuringien‐ sis serovar israelensis*, is widely used against mosquito larvae.

Crops are genetically modified with *Bacillus thuringiensis* (Bt) so as to develop insect resist‐ ance. *B. thuringiensis* produces a diverse group of insecticidal protein toxins with narrow specificity towards different insects (Santie et al, 2011). Bt bacterium contains insecticidal protein crystal that is eaten by insects. The crystal then dissolves in the midgut of the insect. The toxin mixture is released and the proteins are cleaved into active forms. The toxins bind to the midgut cells, assembling a pore that leads to disintegration of the cells, gut paralysis and death. The Bt strains are known to have toxins specific for insects such as caterpillars, beetles, flies and mosquitoes and have little or no effect on mammals. South Africa has been reported to grow more than 85% of the countries cotton and some maize and is the only Af‐ rican country reported so far to grow 67% of the country's total maize production for food (James, 2007) using the Bt insecticides technology. Outside of South Africa, only Burkina Fa‐ so and Egypt allow commercial cultivation of GM crops. Accessibility of these products is, however, relatively restricted, especially in developing countries such as in Africa, due to vocal opposition to GM technology and lack of regulatory mechanisms to deploy such tech‐ nology (Sentie and David, 2011). South African farmers and consumers have already shown a willingness to embrace biotechnology (cotton, maize, and soybean) resulting in improved yield or reduced cost, however, the Bt potato would be the first publicly-funded bioengi‐ neered crop to be released in Africa. Some commercially available Bt varieties and target pests include: *Bacillus thuringiensis*, var. *tenebrionis*- for control of Colorado potato beetle and elm leaf beetle larvae; var. *kurstaki* - for caterpillars; var. *israelensis* – for mosquito, black fly, and fungus gnat larvae; var. *aizawai* for wax moth larvae and various caterpillars, especially the diamondback moth caterpillar.
