Host plants will affect the performance and population dynamics of the polyphagous insect pest Grapholitha molesta (Busck) (Lepidoptera: Tortricidae). Cultivar‐level variability needs to be considered in assessing the performance of G. molesta. We evaluated the fitness of G. molesta on five apple varieties in the laboratory by placing eggs on apples and observing their performance including survival, development, and fecundity of the adult insect. Our results demonstrated differences between indices such as larval duration, pupal weight, egg production, length of tunnel, and exiting rate of larvae, which gave similar host rankings. Variety Danxia was less suitable than Jinqing and Shuohong, and more suitable than Empire and Jinxing. However, other indices such as pupal duration, total pre‐oviposition time, and the estimated population parameters resulted in a different host ranking. We calculated weighted fitness scores to overcome the problem of inconsistent rankings. Empire changed from being the second highest ranking variety based on all population parameters to the second lowest using weighted fitness scores. The difference in ranking observed between apple varieties demonstrates the care needed in predicting population performance in the field using single traits.

The Oriental fruit moth, Cydia molesta (Busck, 1916) (Lepidoptera: Tortricidae), is a key pest of fruit and is widely distributed around the world. There are important connections between its behavior and biology and its management in agriculture, but few studies have investigated the associations between adult behaviors and oviposition. In this study, adult emergence, mating, and reproduction were investigated under laboratory and field conditions. The ratio of females to males at eclosion was approximately 1:1. When one virgin female had access to one virgin male, 66% and 34% of the couples copulated just once and twice, respectively; and the infertility rate of eggs (21.39 ± 1.25%) did not vary daily. Males, given access to one new female daily, could copulate multiple times, whereas females seldom mated more than once, indicating a male-biased operational sex ratio, but mating status of the male parent had no effect on progeny egg reproduction. Also, the number of eggs that hatched by all female partners of a male was inversely proportional to copulation duration for the female laying the eggs for total female reproductive success; and the number of eggs laid by all female partners of a male was proportional to their number of matings for total male reproductive success. However, the total number of eggs that hatched did not significantly differ for eggs laid by a female given new virgin males daily for mating (17.75 ± 4.28) versus eggs laid by virgin females (19.17 ± 7.51) presented daily with a male that re-mated daily with the series of females. Therefore, our results showed that females engaged in mate choice and males engaged in mate competition, affecting egg production, a factor that may be used to enhance mating disruption technology against Cydia molesta.

Grapholita molesta (Busck) (Lepidoptera: Tortricidae), Oriental fruit moth (OFM), attacks fruits and shoots of the economically important trees in Rosaceae. Amygdalin is a cyanogenic glucoside of rosaceous plants that may be related to the seasonal patterns of infestation in many pests. The amygdalin concentration of fruits and shoots of peach, pear, and apple varies over the growing season. However, the relationship between the amygdalin concentration and G. molesta performance has not been reported. Here, we measured the performance (feeding, growth, development, and fecundity) of G. molesta larvae (as subsequent adults) reared on artificial diets with six amygdalin concentrations (0, 3, 6, 12, 24, and 48 mg/g), and we then calculated the population parameters. We found that these different concentrations of amygdalin affected the developmental time and fecundity, except for the proportion of larvae feeding on the diet and the survival rates of larvae and pupae. When compared with the control diet without amygdalin, diets with 3 or 6 mg/g (low and moderate concentrations) of amygdalin shortened developmental times and increased the number of eggs laid by females; however, a diet with 12 mg/g (moderate concentration) of amygdalin only increased the number of eggs laid by females and did not affect the larval and pupal developmental rate. A diet with 48 mg/g (high concentration) of amygdalin prolonged developmental times and reduced the number of eggs laid by females when compared with the control diet without amygdalin. Furthermore, the intrinsic rate of increase (r_m) for insects reared on diets with 3 or 6 mg/g (low and moderate concentrations) of amygdalin versus the control diet without amygdalin showed a slightly improved population growth. However, this increase in the r_m value did not persist over ten successive generations of rearing on the same diet. We concluded that the diet with 6 mg of amygdalin per g of diet can enhance the performance and population growth of G. molesta, but the effects of amygdalin are concentration-dependent.