In China, the rice stem borer (RSB), Chilo suppressalis (Walker) causes (extensive rice damage and yields loss. One of compatible management strategies and methods for an integrated approach to the RSB control is to manipulate RSB’s reproductive behavior, which suppression of pheromonal communication via trapping and interfering mating is a particularly common method. Therefore, it’s very important to understand the mating process, the factors affecting it as well as its role in reproduction. In this study, we focused on RSB mating ability, the effects of delayed mating and male mating history on the longevity and reproductive performance of female RSB under laboratory condition.
When daily paired with 2-day-old virgin males, females normally copulated only once in their whole life span. However, the mating frequency of males was much higher, 2.7 times per life span when they daily paired with 2-d-old virgin females, few males could even mate 4 times during their life span. Female age influenced mating behavior as well: the ratio of mating increased with the age and reached the maximum when females were 2 or 3 days old, then, decreased rapidly with age. The onset time of mating (time after light switched off) would start earlier with the increase of the female age, which ranged from 225.5 min to 120.0 min. However, the duration of mating prolonged as the female mating age increased. On the contrary, both the starting time and duration of mating were not significantly affected by mating age of males.
In another experiment, the mating of virgin male and female RSB moths of different age groups (female 1, 2, 3, 5 and 7 d, and male 1, 2, 3, 4 and 6 d, respectively) were delayed to determine the effects of delayed mating on female longevity, preoviposition period, oviposition periods, fecundity, and egg fertility. The results indicated that female delayed mating significantly influenced the reproductive output and longevity of female RSB. Both female longevity and the preoviposition period increased as female mating age increased, showing positive correlation. When female mated on following night of eclosion, they survived for 6.3 days in average. Longevity increased as mating delayed, which females could survive for 10.2 days when their mating was prolonged for 7 days. And virgin females survived even longer, 10.6 days. However, female delayed mating had negative impact on the oviposition period, fecundity and egg fertility. The oviposition period decreased with the mating delay, depending on the mating age. Oviposition was delayed or disappeared in the absence of mating, and virgin females laid an average of 18 eggs, which indicated that mating could result in the maturation and deposition of eggs. Mean fecundity and egg fertility were 241.3 and 98.3% for the female mating in the day after emergence, and 96.2 and 75.5% for the mating at 7 day after emergence. Both were reduced significantly when mating was delayed over 5 days after emergence. The reduced fecundity and fertility with female mating delay resulted in a 69.4% decrease in the number of viable eggs laid. On the contrary, delayed mating of male had less impact on reproductive output and longevity of female RSB than that of female, no matter how long the male mating had delayed. In addition, we also studied the effect of male mating history on female reproductive output. The results showed that males with different mating history did not result in a significant difference in the quality of their contributions to females.
In conclusion, the female mating delay caused more negative impact on female reproductive potential than that of male. Therefore, reducing the mating rate as well as delaying mating can help us to successfully control RSB in the field using the sex pheromone.