For the first time, a combination of the nuclear sterile insect technique (SIT) with the incompatible insect technique (IIT) has led to the successful suppression of mosquito populations, a promising step in the control of mosquitoes that carry dengue, the Zika virus and many other devastating diseases. The results of the recent pilot trial in Guangzhou, China, carried out with the support of the IAEA in cooperation with the Food and Agriculture Organization of the United Nations (FAO), were published in Nature on 17 July 2019.
SIT is an environmentally-friendly insect pest control method involving the mass-rearing and sterilization of a target pest using radiation, followed by the systematic area-wide release of sterile males by air over defined areas. The sterile males mate with wild females, resulting in no offspring and a declining pest population over time. IIT involves exposing the mosquitoes to the Wolbachia bacteria. The bacteria partially sterilizes the mosquitoes, which means less radiation is needed for complete sterilization. This in turn better preserves the sterilized males’ competitiveness for mating.
While SIT, as part of area-wide insect management strategies, has been successfully used to control a variety of plant and livestock pests such as fruit flies and moths, the control of mosquitoes still had to be demonstrated.
The main obstacle in scaling up the use of SIT against various species of mosquitoes has been overcoming several technical challenges with producing and releasing enough sterile males to overwhelm the wild population. Researchers at Sun Yat-sen University, and its partners, in China, have now successfully addressed these challenges, with the support of the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture, which is leading and coordinating global research in SIT.
For example, the researchers used racks to rear over 500 000 mosquitoes per week that were constructed based on models developed at the Joint FAO/IAEA Division’s laboratories near Vienna, Austria. A specialized irradiator for treating batches of 150 000 mosquito pupae was also developed and validated with close collaboration between the Joint FAO/IAEA Division and the researchers.