Reproductive attributes and functional response of Anastatus japonicus on eggs of Antheraea pernyi, a factitious host.

BACKGROUND: Anastatus japonicus Ashmead (Hymenoptera: Eupelmidae) is a solitary egg endoparasitoid that has been studied for inundative biological control of Halyomorpha halys Stål (Hemiptera: Pentatomidae) in China. In this study, we assessed the reproductive attributes and functional response of Anastatus japonicus on a factitious host, Antheraea pernyi (Guérin-Méneville) (Lepidoptera: Anthelidae) at 25 ± 1 °C, 70 ± 5% relative humidity and 16 h:8 h light/dark photoperiod. RESULTS: The mean lifetime fecundity of Anastatus japonicus females was 404.3 progeny produced over an average oviposition period of 42.3 days. The sex ratio of adult progeny was slightly male biased (51.2%), whereas more female progeny were produced before day 20 of a female's life. Single 1-day-old mated Anastatus japonicus females exhibited a type II functional response to increasing host densities (1-50 eggs), with an inverse host density-dependent pattern of percent parasitism. The upper limit to the daily attack rate was estimated as 7.6 Antheraea pernyi eggs. Furthermore, mutual interference among Anastatus japonicus females occurred when increasing densities of parasitoids (1, 2, 4, 8, 16) were exposed to 30 host eggs. CONCLUSION: Laboratory functional response result revealed that individual Anastatus japonicus might be unable to respond effectively to increasing host density in the field, which could be compensated by releasing larger numbers of wasps. Strong mutual interference among foraging Anastatus japonicus females should be considered in any future inundative biological control programs for the sustainable management of Halyomorpha halys or other host insect pests. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Characterizations of botanical attractant of Halyomorpha halys and selection of relevant deorphanization candidates via computational approach.

Halyomorpha halys has been recognized as a global cross-border pest species. Along with well-established pheromone trapping approaches, there have been many attempts to utilize botanical odorant baits for field monitoring. Due to sensitivity, ecological friendliness, and cost-effectiveness for large-scale implementation, the selection of botanical volatiles as luring ingredients and/or synergists for H. halys is needed. In the current work, botanical volatiles were tested by olfactometer and electrophysiological tests. Results showed that linalool oxide was a potential candidate for application as a behavioral modifying chemical. It drove remarkable attractiveness toward H. halys adults in Y-tube assays, as well as eliciting robust electroantennographic responsiveness towards antennae. A computational pipeline was carried out to screen olfactory proteins related to the reception of linalool oxide. Simulated docking activities of four H. halys odorant receptors and two odorant binding proteins to linalool oxide and nerolidol were performed. Results showed that all tested olfactory genes were likely to be involved in plant volatile-sensing pathways, and they tuned broadly to tested components. The current work provides insights into the later development of field demonstration strategies using linalool oxide and its molecular targets.

Effect of Photoperiod on Longevity, Food Consumption, and Reproduction of Holotrichia oblita (Coleoptera: Scarabaeidae).

Holotrichia oblita (Faldermann) (Coleoptera: Scarabaeidae) is a major soil insect pest that damages forest trees, crops, and lawns. Adults of H. oblita fly, forage, and mate at night but remain underground during the day. We studied the effect of photoperiod on H. oblita reproduction. H. oblita females laid more eggs at 8:16 (L:D) h and 0:24 (L:D) h than other photoperiods. As the scotophase increased, the preoviposition period decreased and the oviposition period increased. Female longevity exceeded that of males at all photoperiods, and both males and females at 0:24 (L:D) h had the shortest longevity. The number of eggs laid per female increased with increasing food consumption. Females at 8:16 (L:D) h had the greatest food consumption and laid the most eggs, while females at 24:0 (L:D) h had the lowest food consumption and laid few eggs. The food intake of adults increased gradually and decreased slowly after reaching a peak. Females began to lay eggs when their food consumption reached a maximum. These results indicate that a scotophase is necessary for the reproduction of H. oblita. A long scotophase promotes greater oviposition. The effect of photoperiod on reproduction is affected by food intake.

Behavioral Evidence and Olfactory Reception of a Single Alarm Pheromone Component in Halyomorpha halys.

Halyomorpha halys is a major herbivore insect in the fruit orchards of China that has become a devastating invasive pest in North America and Europe since its accidental introductions in the 1990s and 2000s, respectively. Like other hemipteran insects, H. halys releases defensive chemicals against natural enemies, including (E)-2-decenal, which is an aldehyde associated with alarm pheromones. In this study, a series of electrophysiological and behavioral tests were conducted to characterize the alarm functions of (E)-2-decenal among H. halys adults and nymphs. An antennal transcriptome was obtained from a Chinese H. halys population, and 44 odorant-binding protein (OBP) genes were annotated. Among them, five putative alarm pheromone-binding proteins were screened and were extremely consistent with their homologs from US populations. These five OBPs were later expressed in a heterologous expression system, harvested, and then challenged with (E)-2-decenal in a binding assay. All five OBPs showed high binding activities to (E)-2-decenal, which demonstrated its behavioral significance as a defensive component in H. halys, as well as being the first report of its olfactory reception. These findings will help develop behavioral-mediating tools as part of integrated pest management approaches to control this invasive pest.