Differential reproductive maturity between geographically separated populations of Homalodisca vitripennis (Germar) in California

The glassy-winged sharpshooter, Homalodisca vitripennis (Germar), is native to the southeastern United States and northeastern Mexico. It was detected in southern California in the late 1980s and in the San Joaquin Valley in 1999, where it transmits the bacterium Xylella fastidiosa to grapevines and other crops. The reproductive success of hybrid and pure line H. vitripennis from two geographically separated populations in California (Riverside (RIV) and Bakersfield (BAK)) was evaluated under identical conditions. The RIV and BAK populations had different preoviposition periods that persisted through the second generation of each lineage. From adult molt, the preoviposition period in both female generations was significantly shorter for RIV (F0 = 28.2 days and F1 = 62.3 days) than BAK females (F0 = 46.1 days and F1 = 170.4 days). After a 21-day mating period, F0 and F1 females deposited on average 391 (range, 21–967) and 196 (range, 0–755) eggs, respectively, without significant differences in fecundity among the F0 and F1 mating pair treatments. Egg accumulation rates among F1 treatments showed that females in the RIV groups rapidly deposited their eggs within the first 120 days after adult molt while BAK females maintained a steady accumulation rate during their life. The performance of both hybrid lines was intermediate between the pure lineages. The F0 mating pairs: ♀RIV × ♂RIV, ♀RIV × ♂BAK, ♀BAK × ♂RIV, and ♀BAK × ♂BAK produced on average 185, 94, 79, and 0 viable eggs, respectively, which suggested a delayed sexual maturity of BAK males and females. The proportion of viable eggs deposited decreased gradually, which suggests that females completely exhausted sperm reserves. From a management perspective, delayed reproductive maturity and polyandry are weak links in H. vitripennis’ biology that may be exploited through mating disruption or insect sterilization strategies to reduce population growth and augment pressure by natural enemies.

Research Highlights► Demonstrated that the preoviposition period (i.e., the number of days from adult molt to first oviposition) of Homalodisca vitripennis in two female generations was significantly shorter for insects originated from a population in Riverside (F0 = 28.2 days and F1 = 62.3 days) than Bakersfield, California (F0 = 46.1 days and F1 = 170.4 days). ► Demonstrated a gradual decrease in the number of viable eggs deposited by H. vitripennis females, which suggests that females can exhaust sperm reserves and thus, re-mating may be necessary to successfully produce progeny. Mating disruption strategies or improved timing of insecticide applications may have the potential to reduce population growth by reducing the number of fertilized eggs produced. ► Based on the deposition of viable eggs, the majority of tested H. vitripennis required a period longer than 21 days to achieve sexual maturity, which differs from previous reports that the majority of H. vitripennis females would mate within 7 days posteclosion and store sperm for the rest of their life. ► Finally, data support the hypothesis that oviposition rate after summer months is an additional key mechanism regulating the population growth of H. vitripennis in different environments in California. Precise knowledge for each of these factors is pivotal to the success of pest control and critical for development and implementation of management strategies aimed at suppressing H. vitripennis populations.