The Sterile Insect Technique

Daniel Starwalt
July 17, 2015

Submitted as coursework for PH241, Stanford University, Winter 2015

The Issue

Fig. 1: First pest eliminated in an area using SIT. (Source: Wikimedia Commons)

Farmers versus pests is a battle for the ages that will never be completely solved. Today there are many ways that Farmers protect their crops. The most common understood pest repellant for farming, is the use of pesticides, in which a poison is used, to kill the insects or pests but not harm the crops. The issue with pesticides is that, although the pesticides are not meant to harm the crop, there are traces of pesticides found on produce, even when brought to market. It is well known that pesticide residue is found on produce at the market. The EPA is in control of how much of this pesticide residue will be tolerated on the produce. There a varying amounts of residue that are tolerated depending on the product or produce. The issue is that, insects and other pests will always be a problem to farmers and their crops. The underlying issue is that the current solution, to rid the crops of pests is to kill them with pesticides. Although the pesticides do not harm the crops, the residues on the produce pose a harm for the consumers.

The Solution

There are many alternatives to pesticides when it comes to protecting crops from pests. One alternative way that stands out from the rest is called the Sterile Insect Technique (SIT). The SIT is used in situations, where one specific, insect is overwhelming a crop. The females of the insects are the ones who cause the the damage to the crops by laying eggs in them. The SIT was developed to extinguish the problem of the female insects before they can lay their eggs and harm the crop. SIT is used by first using X-ray radiation to sterilize the male insects so they are not able to produce. Once the male insects are sterilized, they are then released in a large number to go out and mate with their female counterparts who are causing damage to the crops. Once the males are released and mate with the females, the females will not be able to reproduce, and thus will eventually die, not enlarging the population. If the females are only able to mate with sterile males, then the population will diminish and the targeted specie of insect may even cease to exist in the specific area where the sterile males were released [1].

The Downsides to SIT

The SIT is an effective way to eliminate, a specific species of problem insects. But there are many issues with the SIT, that are keeping it from being in use all over. One issue is that, for some pests there is no cheap, fast, or effective way to sort through the pests in a large number, and determine whether they are male or female. Another issue is that the amount of radiation used to sterilize the insects, is too damaging to the insects will just die. This makes sterilizing insects a tricky process who must be run by personnel who have high levels of training [2].

The Upsides to SIT

The largest and most important upside to the SIT is that it is environmentally clean and sustainable. Another positive for the SIT is that if farmers are having issues with one specific problem insect, then they would be able to use the SIT in order to rid their crops of said problem insect. The SIT reduces the need for generic pesticides or insecticides that will leave harmful residues on the crops.

What Is Used to Sterilize the Insects?

Exposing the insects to ionizing radiation is the current method of choice, when it comes to sterilizing insects so they may no longer produce. Isotopic sources such as cobalt-60 or cesium-137 are used to produce gamma radiation for sterilizing the insects. X-rays and high energy elections are other useful ways in which insects may be exposed to radiation [3]. The most important factor when radiating insects for sterilization, is the amount of radiation that is absorbed by the insect. This factor is extremely important, and must be controlled very closely, in order for the insects to be unable to reproduce, but still be strong enough to mate and compete with other wild insects. Insects range when it comes to the amount of radiation that is absorbed by each particular insect. The range is from as little as below 5 Gy all the way up to and some even beyond 300 Gy [2]. Each insect species has its own Gy value that is needed in order for it to be sterilized, what is tricky is that factors such as the age or the oxygen levels of the insect come into play when determining how radiation each insect species will absorb.

The Future

The SIT technique is the insect control technique of the future. In a world demanding for cleaner foods and environments the SIT will thrive. It is an eco-friendly way of reducing the number of problem pests in an area. The only thing that must be done in order for the SIT to be able to expand further and overtake conventional pesticides and insecticides, is that the technique must be able to expand and encompass more key problem species of insects.

© Daniel Starwalt. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.


[1] J. E. Brody, "Scientists Press War on Insect Pests' Birth Rate; Residues Abound Other Insect Lures Hormone Under Study," New York Times, 26 Nov 67.

[2] W. Sullivan, "Use of Radiation on Insects Hailed," New York Times, 12 Sep 64.

[3] W. Sullivan, "Mass Production of Male Flies Raises Hopes for Eradication," New York Times, 1 May 71.