Damage from insect pests can endanger farmers’ livelihoods and affect international trade and global food security, all of which restrict the movement of some plants to contain the spread of pests. However, exposure to such pests can be slowed down, and in some cases completely eliminated, by harnessing the power of nuclear engineering. The technology used requires the mass rearing of insects, which, thanks to the new knowledge, can become more efficient.
The IAEA, in partnership with the United Nations Food and Agriculture Organization (FAO), has been researching and improving sterile insect technology (SIT) for 60 years to help countries fight diseases that insects transmit. The FAO estimates that between 20 and 40 percent of the world’s harvests are lost to pests each year. This corresponds to a loss of sales of around $ 220 billion for farmers. As an environmentally friendly form of insect population management, SIT uses radiation to sterilize male insects. The sterilized male insects are then released into target areas to breed with wild females. This results in no offspring and minimizes damage to the plants from insects that may burrow into or ingest the plant.
The daily production and release of millions of sterile men who are healthy and able to compete against wild men is key to the success of an SIT program. Participants in a Coordinated Research Project (CRP) comparing the rearing performance and competitiveness of sterile male strains produced using genetic, transgenic or symbiote-based technologies have explored the challenges associated with this process and ways to overcome them. As a result of the CRP, a collection of articles has now been published highlighting the achievements of research.
Sexing of the fruit fly
Ideally, to ensure effective SIT programs, insects must be segregated by sex, which is a challenging and arduous task for many species. “The active component of SIT are the male insects, and we have now been able to isolate and use genetically selectable markers that can be used to identify and differentiate men from women,” said Konstantinos Bourtzis, molecular biologist at the FAO / IAEA Insect Pest Control Laboratory. “With male-only releases, we can ensure that SIT is cheaper and more effective at suppressing a target insect population as women lay eggs in the harvest.”
Over a period of five years, the CRP participants compared the efficiency of different technologies for producing sterile male insect strains. The project involved 18 scientists from 13 countries who studied a range of technologies and sterilization capabilities.
As the first research project on the South American fruit fly (Anastrepha fraterculus), the project was able to find a genetic marker and link it to the gender of the fly as a result of the development of a genetic sex strain (GSS) (see What is a genetic sex strain (GSS)?). The marker, black in women and brown in men, is observed at the pupal stage and can identify the gender of the fly earlier than before. With this marker, the female pupae in a production facility can be automatically separated from the males so that only males can be sterilized and transported and released into target areas.
Now that there is a marker that will allow sex segregation at the pupal stage of the South American fruit fly, the next step is to assess the strain’s genetic stability and biological quality under mass rearing conditions and to evaluate its efficiency under field conditions.
“In South America, a GSS strain is critical to the implementation of a mass rearing facility and field project,” said José Salvador Meza Hernández, deputy director of Genetic Sexing Laboratories as part of the Moscafrut Operating Program at the Inter-American Institute for Agricultural Cooperation in Chiapas, Mexico, and principal researcher in the CRP. “The recent discovery of pupae marker and its use in building GSS based on black pupae has great potential to increase the effectiveness and reach of SIT in the region.”
Towards More Sterilized Flies Another major achievement of this project was the refinement of strains to improve genetic stability. Men could have a certain desired trait, such as: For example, improved rearing performance, gender separation, genetic stability or the competitiveness of mating These refinement efforts took place with the Mediterranean fruit fly (Ceratitis capitata), the Mexican fruit fly (Anastrepha ludens), the New World screwworm (Cochliomyia hominivorax), the yellow fever mosquito (Aedes aegypti) and the Asian tiger mosquito (Aedes albopictus).
“We need to mass-produce males of high biological quality in a cost-effective manner for sterilization and release,” said Bourtzis. “They have to compete with wild men. If they fail to do this, we cannot suppress the target population.”
A CRP follow-up is currently in progress, focusing on developing generic approaches to building GSS. This research on GSS and the development of strategies for building GSS will be assessed in terms of the efficiency, applicability, and transferability of GSS in a number of ways. The successes of generic approaches to GSS are then assessed through small-scale tests for their application in SIT projects.