Does the source matter for SIT? Negligible effects of irradiator source, X-ray vs. gamma, for
sterilization and sterile male mating competitiveness in the mosquito Aedes aegypti.

Sterile insect technique (SIT) has proven to be very effective as a key component in area-wide integrative pest management for multiple agricultural pests, and in recent years interest has been growing in applying SIT to mosquito vectors of importance to human health. SIT may be particularly useful for peridomestic disease vectors like Aedes aegypti that live in close proximity to humans, occupy cryptic larval breeding sites with adults that rest in places difficult to reach with sprays, and that have some populations showing resistance to common chemicals used in mosquito control. For SIT, males are typically sterilized by exposing them to gamma radiation. However, these irradiators typically use Co-60 or Cs-137; high activity sources that are vulnerable to theft or misuse and thus require substantial security and monitoring. In support of the National Nuclear Security Administration (NNSA) Office of Radiological Security (ORS) mission to reduce the risk of these sources by encouraging use of non-radioisotopic technologies, Sandia National Laboratories has funded a study to compare the efficacy of gamma versus Xray-based irradiation for SIT. Specifically, this study seeks to compare an established Cs-137 gamma irradiator used for an operational Ae. aegypti SIT pilot program with a new X-ray irradiator for sterilizing male pupae and adults while maintaining male performance after irradiation. We show negligible differences in efficacy of sterilization or post-irradiation male performance between the X-ray and gamma sources. Our results show that insect SIT programs can successfully transition from gamma to X-ray sources and suggests that new programs can begin their programs using X-ray irradiation sources to avoid regulatory and cost hurdles associated with installation of new gamma-radiation sources, overall showing that X-ray irradiators provide a viable alternative technology to radioactive gamma sources for insect pest control.