Differential Flight Capacity of Spissistilus festinus (Hemiptera: Membracidae) by Sex and Age

The three-cornered alfalfa hopper (TCAH), also known as Spissistilus festinus (Hemiptera: Membracidae), infests legumes and poses a threat to the grapevine industry by acting as a vector for grapevine red blotch virus (GRBV), which causes red blotch disease. Assessing TCAH flight capacity is key for understanding the risk of GRBV transmission. In this study, we examined the flight propensity and flight capacity of male and female TCAH using a flight mill apparatus under laboratory conditions. Our results revealed that sex and age had a significant effect on flight capacity. As insects aged, their flight capacity increased, with two-to-seven-day-old insects flying for shorter durations and covering shorter distances compared to mature insects (≥ eight days). Moreover, male insects exhibited significantly longer and farther flights compared to females, with an average flight capacity of 570.22 m for males and 239.57 m for females. Flight propensity, however, was not influenced by sex or age, as 88% (37/42) of males and 70% (31/44) of females engaged in flight. We observed that female TCAH were heavier and possessed larger wings than males. Nevertheless, wing loading and wing aspect ratio were similar between sexes, suggesting that morphological characteristics were not responsible for the observed differences in flight capacity. Our findings indicate that males have a greater capacity for GRBV dispersal compared to females, thereby providing a foundation for assessing the risk of GRBV spread facilitated by TCAH in vineyards.