The concept of Sterile Insect Technique (SIT)

The sterile insect technique (SIT) is arguably the most ecologically-compatible means of pest control in existence. It is not a stand-alone technology, but should be integrated with other pest management technologies, such as bait application and sanitation, in an area-wide programme.

Simply put, SIT is birth control for insects. It is used primarily to control or eradicate insect pests, usually crop pests or human and animal pests. The target insect is reared in great numbers, and the males sterilized, usually using gamma radiation. The sterile males are released weekly in high numbers in the target areas, usually throughout the year. They mate with the wild females which results in infertile eggs being laid, and provided certain other population management activities are properly carried out, the wild population then declines rapidly.

Released sterile males compete with the wild males for mating with females. A high ratio of sterile males to wild males is therefore required. A key requirement of SIT is therefore that the sterile males be released into areas where the wild fruit fly population has been previously reduced to very low levels. If this is not done, there will be too many wild males mating with wild females, and the population will not decrease. Reduction of the wild fruit fly population to low levels before sterile releases commence is therefore essential.

Furthermore:

  • It is a proven technique, used in a number of other countries to create fruit fly-free areas, and can be very cost-effective.
  • It is an area-wide technique – it must be applied over large areas, e.g. 500 ha and larger.
  • SIT is highly environmentally friendly, making it very acceptable to export markets, which increasingly focus on ecologically compatible production techniques.
  • Depending on the size of the area under SIT and other factors, there are various options for release of sterile fruit flies, which can have a favourable impact on the cost-effectiveness of SIT.
  • SIT is management intensive – it requires very good coordination, and the cooperation of all the growers in an SIT area.