Does environment influence sweetpotato weevil host plant resistance?

Sweetpotato weevil, Cylas formicarius elegantulus (Summers) (Coleoptera: Brentidae), is the primary pest of sweetpotato in subtropical regions of North America.  Adult feeding induces terpene production and larval tunneling reduces yield, both limiting marketability. In Louisiana, sweetpotato is grown under varied environmental conditions; from sandy/silty alluvial soils that are irrigated to loamy loess soils that are under dryland protection. These varied growing conditions provide an opportunity for assessing whether environment impacts host plant resistance. Cultivars Beauregard (susceptible), Vermillion (resistant), and Murasaki (resistant) were grown at three locations in Louisiana under the same growing practices. The only difference in growing conditions was soil type and rainfall. At harvest, storage roots of similar size from each variety were selected and used adult emergence assays. In no-choice tests, ten storage roots of each variety were exposed individually to six gravid females which oviposited for four days and were then removed. After thirty days, adult emergence was counted tri-weekly for thirty-five days. Results showed the effect of location and variety had significant impact on adult emergence. This indicates different environmental conditions can alter host plant resistance.