Abstract: Sterile Insect Technique (SIT) is a species-specific pest control technique used to target Aedes mosquitoes. Benefits of SIT include increased effectiveness of control of pesticide-resistant populations and minimizing harm to non-target organisms. There are environmental contexts in which SIT will release larvae from competition, which may yield the same, or even increased, adult production. Such environmental contexts are strongly influenced by the larval environment, because Aedes larvae experience negative density dependent effects – i.e., the size and survivorship of larvae decreases with increasing density. Thus, it is important to identify these environmental contexts, so we can avoid them and maximize the effectiveness of population management using SIT. I hypothesized that SIT is effective when resource level and larval density do not result in strong negative-density dependent effects on adult production. I predicted that SIT will be effective in the early summer, when Aedes albopictus populations are low. I further predicted that SIT would yield more adults in the late season in containers with low resource levels.
We collected Aedes eggs, water, and detritus from 26 containers placed in the field for one week, then transferred the field material to controlled lab conditions. We simulated larval density reduction by SIT as a treatment by adding Ae. albopictus at 50% or 25% of the observed egg density for the associated field container; we added Ae. albopictus at the original egg density to control containers. We collected detritus resources from the field containers weekly and added those to the corresponding experimental containers. We conducted this experiment in summer of 2022 – once in June and again in August, when Aedes abundances were expected to be low and high, respectively.
We recorded the number of adult Ae. albopictus that emerged from each experimental container. Resource levels did not affect the number of adult Ae. albopictus emerging in either the control or simulated SIT containers in June. Preliminary analysis from the August experiment shows that there are a range of egg densities where simulated SIT, at 50% and 75% mortality, increased or did not change the number of emerging adults compared to control containers. Our results suggest that targeting Ae. albopictus with SIT in June when Aedes abundances are low would be an effective control measure. Our research shows how extrinsic mortality can result in different outcomes at different times of the year for populations that fluctuate in size annually.
