Evaluation of large volume yeast interfering RNA lure‐and‐kill ovitraps for attraction and control of Aedes mosquitoes

Abstract

Aedes mosquitoes (Diptera: Culicidae), principle vectors of several arboviruses, typically lay eggs in man‐made water‐filled containers located near human dwellings. Given the widespread emergence of insecticide resistance, stable and biofriendly alternatives for mosquito larviciding are needed. Laboratory studies have demonstrated that inactivated yeast interfering RNA tablets targeting key larval developmental genes can be used to facilitate effective larvicidal activity while also promoting selective gravid female oviposition behaviour. Here we examined the efficacy of transferring this technology toward development of lure‐and‐kill ovitraps targeting Aedes aegypti (L.) and Aedes albopictus (Skuse) female mosquitoes. Insectary, simulated field and semi‐field experiments demonstrated that two mosquito‐specific yeast interfering RNA pesticides induce high levels of mortality among larvae of both species in treated large volume containers. Small‐scale field trials conducted in Trinidad, West Indies demonstrated that large volume ovitrap containers baited with inactivated yeast tablets lure significantly more gravid females than traps containing only water and were highly attractive to both A. aegypti and A. albopictus females. These studies indicate that development of biorational yeast interfering RNA‐baited ovitraps may represent a new tool for control of Aedes mosquitoes, including deployment in existing lure‐and‐kill ovitrap technologies or traditional container larviciding programs.

Field trials reveal the complexities of deploying and evaluating the impacts of yeast-baited ovitraps on Aedes mosquito densities in Trinidad, West Indies

“…In general, the rainy season oviposition patterns in 10 L ovitraps distributed in the Curepe neighborhood were similar to those observed in a previous study on the adjacent University of the West Indies campus, with the greatest average egg numbers per trap occurring during August 34 . This pattern is also consistent with that observed for St. Joseph, Trinidad in 1988 using 400 ml ovitraps 23 , 24 .…”

“…In this investigation, we sought to obtain baseline information on the logistics associated with efforts directed toward large-scale deployment of yeast interfering RNA lure-and-kill ovitraps in a residential neighborhood in Curepe, Trinidad, West Indies. In a previous study conducted on the University of the West Indies campus, adjacent to Curepe, we determined that large 10 L ovitrap containers baited with yeast interfering RNA tablets were significantly more attractive than identical but unbaited containers to gravid A. aegypti and A. albopictus females 34 . As a proxy for simulating 100% lethality, our ovitraps were lined with seed germination papers that were removed and replaced weekly throughout the rainy season.…”

“…Our previous laboratory assays with small volume (500 ml) containers have shown that gravid A. aegypti females were significantly more likely to oviposit in those baited with yeast compared to those with water only 30 . Subsequent laboratory and semi-field studies in Indiana, USA, as well as small-scale field trials in Trinidad, West Indies, all conducted with large volume ovitraps (7.5 L or 10 L) confirmed a preference to oviposit in those baited with yeast by A. aegypti as well as A. albopictus females 34 . In this study, we conducted a preliminary, small-scale field trial in neighborhoods around Curepe, Trinidad.…”

A Yeast RNA-Interference Pesticide Targeting the Irx Gene Functions as a Broad-Based Mosquito Larvicide and Adulticide

“…The ability of these insecticides to kill both larvae and adults opens opportunities to design integrated RNAi mosquito control programs in which a combination of methods, such as larvicidal treatment of breeding sites with interfering RNA larvicides, larval lethal lure-and-kill interfering RNA ovitraps [17], and RNAi-ATSBs is used simultaneously. Recent studies have uncovered a high level of acceptance of yeast RNAi-based larvicides and ovitraps among stakeholders in Trinidad and Tobago [59,60].…”

“…Laboratory evaluation of several different interfering RNA delivery mechanisms resulted in the identification of baker's yeast (Saccharomyces cerevisiae) as a promising method for oral transfer of interfering RNA to mosquitoes. S. cerevisiae is an excellent system for producing interfering RNA [4], and yeast is a potent odorant attractant for both gravid adult mosquitoes, which are lured to lay eggs in yeast-treated containers [17], as well as mosquito larvae, which readily consume larvicidal yeast upon hatching [9]. Moreover, the selection of S. cerevisiae, a model organism that is amenable to genetic manipulation, has facilitated generation of multiple yeast interfering RNA larvicide strains, each one targeting a different gene required for mosquito survival, resulting in the creation of an arsenal of yeast IRPs to combat pesticide resistance [4,5].…”