Host plant preference during the larval stage may help shape not only phenotypic plasticity but also behavioral isolation. We assessed the effects of diet on population parameters and mate choice in Spodoptera litura. We raised larvae fed on tobacco, Chinese cabbage, or an artificial diet, and we observed the shortest developmental time and highest fecundity in individuals fed the artificial diet. However, survival rates were higher for larvae on either of the natural diets. Population parameters including intrinsic rate of increase and finite rate of increase were significantly higher with the artificial diet, but this diet led to a lower mean generation time. Copulation duration, copulation time, and number of eggs reared significantly differed between diets. In terms of mate choice, females on the artificial diet rarely mated with males fed on a natural host. Our results support the hypothesis that different diets may promote behavioral isolation, affecting mating outcomes. Thus, findings for populations fed an artificial diet may not reflect findings for populations in the field.

Spodoptera litura is an important pest that seriously affects Asparagus officinalis production. To clarify the population characteristics and feeding preference of S. litura on different asparagus tissues, asparagus stems and leaves were selected as the research objects, related studies were conducted by constructing the life table and the feeding preference experiment. The results showed that S. litura could complete its development and reproduction normally on asparagus stems or leaves. Although the adult longevity and fecundity of S. litura on the two types of tissues were not significantly different, the development duration of larvae and pupae, and total preoviposition period on leaves were significantly longer than those raised on stems. The intrinsic rate of increase and finite rate of increase were 0.186 d⁻¹ and 1.204 d⁻¹ on stems, which were significantly higher than those fed on leaves (0.161 d⁻¹ and 1.175 d⁻¹). The mean generation time on stems (32.88 d) was significantly lower than on leaves (36.88 d). It indicated that stems were more suitable for its population growth. In the feeding preference, the third and fifth instar larvae preferred to feed on leaves, and other instar larvae (except for the sixth instar of 2.5 h) had no significant difference. These results will provide a theoretical reference for further research and forecasting and integrated control.

Efficient rearing is necessary for the successful biological control of pests. The braconid wasp, Microplitis manilae, is a natural solitary parasitoid of larval Spodoptera frugiperda. However, the effect of the host diet on the parasitism success of M. manilae on S. frugiperda larvae remains unclear. Here, we determined the parasitism rate, oviposition, eclosion rate, developmental period and offspring sex ratio of M. manilae parasitizing S. frugiperda fed with fresh corn leaves or an artificial diet. M. manilae parasitizing the corn leaf‐fed S. frugiperda larvae exhibited a significantly higher parasitism rate (40%), oviposition (62.50 eggs/female) and eclosion rate (81.38%) than the wasp parasitizing the artificial diet‐fed S. frugiperda larvae (22%, 38.33 eggs/female, and 58.73%, respectively). Furthermore, M. manilae parasitizing the corn leaf‐fed S. frugiperda larvae exhibited a significantly shorter developmental period (16.35 days) and lower sex ratio (1.17) than the wasp parasitizing the artificial diet‐fed S. frugiperda larvae (18.00 and 2.15 days, respectively). Overall, M. manilae exhibited better parasitic success on corn leaf‐fed S. frugiperda larvae than on artificial diet‐fed S. frugiperda larvae. Therefore, using fresh corn leaf‐fed S. frugiperda is the most suitable strategy for mass‐rearing M. manilae for pest biocontrol. Our findings suggest M. manilae as an effective biocontrol candidate for controlling S. frugiperda in corn fields.

The braconid wasp Microplitis manilae (Hymenoptera: Braconidae) is a solitary, koinobiont endoparasitoid of young Spodoptera litura (Fabricius) larvae and one of its most crucial natural parasitic enemies. The establishment of a stable and sufficient population of M. manilae by rearing them in a laboratory is the cornerstone of field release management. However, when reared in a laboratory, M. manilae is affected by temperature. Here, we attempted to optimize the rearing temperature of M. manilae for parasitizing second-instar S. litura larvae by examining the effects of rearing at 5 temperatures: 16 °C, 20 °C, 24 °C, 28 °C, and 32 °C. Our results suggest that the development of the parasitoid progeny speeded up with shorter durations of the egg–larval, pupal, and preadult stages with the increase in temperature from 16°C to 32 °C. The parasitism rate and fecundity of M. manilae upon parasitizing second-instar S. litura larvae increased with rearing temperature from 16°C to 24 °C, with the peaks at 24 °C reaching 52.90% and 111.70 eggs/female, respectively, and then decreased at 28 °C to 32 °C. At 24 °C, the sex ratio (0.22) was the lowest, whereas the emergence rate (68.54%) did not differ significantly compared with those at other temperatures. Meanwhile, at 28 °C, the parasitism rate, fecundity, and emergence rate approached the levels at 24 °C, whereas the sex ratio was higher (0.29) than at 24 °C. These findings suggest 24 °C to 32 °C is the most appropriate temperature range for M. manilae mass rearing under laboratory conditions.

Delayed mating is an effective strategy that can decrease the fecundity of a pest by reducing the time that females have to mate. This disruption does not completely inhibit mating and may lead to multiple matings. The effects of delayed mating with multiple partners on different indexes of mating in female and male Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) were determined in this study. The delay in mating significantly decreased the number of matings and the mating success of both sexes and the male contribution to reproduction. Compared with the effect on female fecundity, the delayed mating with multiple partners had a greater effect on the male mate contribution to fecundity. The longevity of females and males increased significantly with a 72 h delay in mating. Linear regression analysis showed negative relationships between delayed mating and fecundity and number of matings in both sexes. Thus, delayed mating with multiple partners can disrupt the mating and reproductive potential of S. litura.

Biological control is an effective and sustainable method of integrated pest management. Microplitis manilae (Hymenoptera: Braconidae) is a common internal parasitoid wasp of the order Lepidoptera. To determine a suitable host species for the reproduction of parasitoids, it is essential to assess host suitability and parasitic potential of the parasitized pests. Herein, we investigated host selection and exploitation of M. manilae. We evaluated the parasitic efficacy of M. manilae in 4 pest species in the Spodoptera and Mythimna genera of the Noctuidae family. The results indicated that the parasitism rate of M. manilae on 3 species in the Spodoptera genus is higher than on Mythimna separata in the Mythimna genus, with M. manilae exhibiting a higher parasitism rate and shorter development duration on Spodoptera litura compared to other species. The parasitism rate for 1st instars hosts was 86.67 ± 0.04%, while the development duration was 14.1 ± 0.03 days. However, when parasitizing the 3rd instar of Spodoptera frugiperda, parasitoids showed a higher sex ratio, of 0.71 ± 0.05. Additionally, M. manilae had parasitic effect on M. separata, providing a new choice for its parasitism. The results identify the optimal host, which could enhance and reproduction rate and survival rate of M. manilae, thus facilitating their large-scale propagation. Understanding the parasitic effects of M. manilae on pests can further its field application, also plays a major role in promoting the development of biological control technologies and sustainable agricultural production.