Monitoring of the sugarcane aphid feeding behavior across multiple developmental stages of sorghum

Sorghum is the fifth most produced cereal in the world due to its high nutritional properties and also a good source of bioactive compounds important to human health. Sugarcane aphid (SCA) is a piercing-sucking type key pest of sorghum. Although SCA had been reported in the US earlier, it started to expand their populations becoming an important pest of sorghum in the United States since 2013. Previously, it was reported that SCA reproduction varies between younger and older sorghum plants. However, mechanisms involving sorghum resistance to SCA in different developmental stages are not well understood. In this study, we used the Electrical Penetration Graph (EPG) to monitor the aphid feeding behavior in two- and six-week-old sorghum BTx623 plants. The EPG data revealed that aphids spent more time in the sieve element phase on six-week-old plants compared to two-week-old plants. We also found significant differences in the pathway phase and time spent to reach the first sieve element phase between two-week and six-week-old plants. In addition, a no-choice bioassay was performed to assess the SCA population growth between the different developmental stages. In summary, SCA population number was higher in two-weeks-old plants and lower in six-weeks-old plants.