Involvement of Chemosensory Protein CrufCSP3 in Perception of the Host Location in a Parasitic Wasp Cotesia ruficrus.

Chemosensory proteins (CSPs) constitute a class of olfactory proteins localized in insect sensory organs that serve a crucial function in decoding external chemical stimuli. This study aims to elucidate the involvement of CrufCSP3 in olfactory perception within the context of Cotesia ruficrus, an indigenous endoparasitoid targeting the invasive pest Spodoptera frugiperda. Through fluorescence-competitive binding assays and site-directed mutagenesis, we pinpointed four amino acids as pivotal residues involved in the interaction between CrufCSP3 and five host-related compounds. Subsequent RNA interference experiments targeting CrufCSP3 unveiled a reduced sensitivity to specific host-related compounds and a decline in the parasitism rate of the FAW larvae. These findings unequivocally indicate the essential role of CrufCSP3 in the chemoreception process of C. ruficrus. Consequently, our study not only sheds light on the functional importance of CSPs in parasitic wasp behavior but also contributes to the development of eco-friendly and efficacious wasp behavior modifiers for effectively mitigating pest population surges.

Characterization of CrufCSP1 and Its Potential Involvement in Host Location by Cotesia ruficrus (Hymenoptera: Braconidae), an Indigenous Parasitoid of Spodoptera frugiperda (Lepidoptera: Noctuidae) in China.

Chemosensory proteins (CSPs) are a class of soluble proteins that facilitate the recognition of chemical signals in insects. While CSP genes have been identified in many insect species, studies investigating their function remain limited. Cotesia ruficrus (Hymenoptera: Braconidae) holds promise as an indigenous biological control agent for managing the invasive pest Spodoptera frugiperda (Lepidoptera: Noctuidae) in China. This study aimed to shed light on the gene expression, ligand binding, and molecular docking of CrufCSP1 in C. ruficrus. A RT-qPCR analysis revealed that the expression of CrufCSP1 was higher in the wings, with male adults exhibiting significantly higher relative expression levels than other developmental stages. A fluorescence competitive binding analysis further demonstrated that CrufCSP1 has a high binding ability with several host-related volatiles, with trans-2-hexenal, octanal, and benzaldehyde showing the strongest affinity to CrufCSP1. A molecular docking analysis indicated that specific amino acid residues (Phe24, Asp25, Thr53, and Lys81) of CrufCSP1 can bind to these specific ligands. Together, these findings suggest that CrufCSP1 may play a crucial role in the process of C. ruficrus locating hosts. This knowledge can contribute to the development of more efficient and eco-friendly strategies for protecting crops and managing pests.

Comparative studies of ovipositional preference, larval feeding selectivity, and nutritional indices of Spodoptera frugiperda (Lepidoptera: Noctuidae) on 6 crops.

The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith), is a significant invasive pest identified as a serious threat to global agricultural production and food security. However, its ovipositional preference, larval feeding selectivity, and nutritional indices are less studied. Here, we investigated these traits of FAW when fed on maize, wheat, soybean, tomato, cotton, and Chinese cabbage, and analyzed the correlation between its nutritional indices and the nutritional contents of crops. The results showed that the highest number of eggs were laid on maize and the lowest number were laid on tomato. The highest feeding choice rate of third instar larvae was on maize, and the lowest was on Chinese cabbage. The fifth instar larvae showed the highest feeding choice rate on maize, but no significant differences were found among other crop species. The food consumption (FC), the relative growth rate (RGR), and the approximate digestibility (AD) were significantly higher on maize and wheat, while the efficiency of conversion of ingested food (ECI) and the efficiency of conversion of digested food (ECD) were significantly higher when fed on cotton and Chinese cabbage. The FC, the relative consumption rate (RCR), RGR, and AD were significantly and positively correlated with soluble sugar and protein contents of host plants, while the ECI and ECD were significantly and negatively correlated with the soluble sugar content. The present study indicates that FAW may cause potential economic losses to these crops besides maize, and these findings are valuable in managing and controlling this pest.

Fall Armyworm Gut Bacterial Diversity Associated with Different Developmental Stages, Environmental Habitats, and Diets.

The fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae), is a major invasive pest that seriously threatens world agricultural production and food security. Microorganisms play a crucial role in the growth and development of insects. However, the diversity and dynamics of gut microbes with different developmental stages, environmental habitats, and diets in S. frugiperda remain unclear. In this study, we found the changes of the microbiome of S. frugiperda across their life stages, and the bacteria were dominated by Firmicutes and Proteobacteria. The community composition of the egg stage was quite different from other developmental stages, which had the highest community diversity and community richness, and was dominated by Proteobacteria. The bacterial community compositions of male and female adults were similar to those of early larvae stage (L1-L2), and operational taxonomic units (OTUs) with abundant content were Enterococcus and Enterobacteriaceae bacteria, including Enterobacteria, Klebsiella, Pantoea, and Escherichia. The third instar larvae (L3) mainly consist of Enterococcus. The late stage larvae (L4-L6) harbored high proportions of Enterococcus, Rhodococcus, and Ralstonia. There was no significant difference in gut microbial composition between field populations and laboratory populations in a short period of rearing time. However, after long-term laboratory feeding, the gut microbial diversity of S. frugiperda was significantly reduced. Enterococcus and Rhodococccus of S. frugiperda feeding on maize showed higher relative proportion, while the microbial community of S. frugiperda feeding on artificial diet was composed mainly of Enterococcus, with a total of 98% of the gut microbiota. The gene functions such as metabolism, cell growth and death, transport and catabolism, and environmental adaptation were more active in S. frugiperda feeding on corn than those feeding on artificial diet. In short, these results indicate that developmental stage, habitat, and diet can alter the gut bacteria of S. frugiperda, and suggest a vertical transmission route of bacteria in S. frugiperda. A comprehensive understanding of gut microbiome of S. frugiperda will help develop novel pest control strategies to manage this pest.

Melanin synthesis genes BgTH and BgDdc affect body color and cuticle permeability in Blattella germanica.

Melanin is involved in cuticle pigmentation and sclerotization of insects, which is critical for maintaining structural integrity and functional completeness of insect cuticle. The 2 key enzymes of tyrosine hydroxylase (TH) and dopa decarboxylase (DDC) predicted in melanin biosynthesis are usually conserved in insects. However, it is unclear whether their function is related to epidermal permeability. In this study, we identified and cloned the gene sequences of BgTH and BgDdc from Blattella germanica, and revealed that they both showed a high expression at the molting, and BgTH was abundant in the head and integument while BgDdc was expressed highest in the fat body. Using RNA interference (RNAi), we found that knockdown of BgTH caused molting obstacles in some cockroaches, with the survivors showing pale color and softer integuments, while knockdown of BgDdc was viable and generated an abnormal light brown body color. Desiccation assay showed that the dsBgTH-injected adults died earlier than control groups under a dry atmosphere, but dsBgDdc-injected cockroaches did not. In contrast, when dsRNA-treated cockroaches were reared under a high humidity condition, almost no cockroaches died in all treatments. Furthermore, with eosin Y staining assay, we found that BgTH-RNAi resulted in a higher cuticular permeability, and BgDdc-RNAi also caused slight dye penetration. These results demonstrate that BgTH and BgDdc function in body pigmentation and affect the waterproofing ability of the cuticle, and the reduction of cuticular permeability may be achieved through cuticle melanization.

Improvement of Bemisia tabaci (Hemiptera: Aleyrodidae) Fitness on Chinese Kale upon Simultaneous Herbivory by Plutella xylostella (Lepidoptera: Plutellidae).

Bemisia tabaci and the diamondback moth (DBM), Plutella xylostella, are two major cosmopolitan pests that often occur together and cause severe economic losses to cruciferous crops. However, little is known about how they interact with each other. To determine the effects of defense responses induced by the two pests on the biology and population dynamics of the herbivores, we studied the performance and fitness of B. tabaci and DBM when they damaged Chinese kale simultaneously and in different orders. The results showed that DBM pre-infestation shortened the developmental duration, increased longevity, oviposition days, and fecundity of B. tabaci. Meanwhile, the intrinsic rate of increase (r), net reproductive rate (R0) and finite rate of increase (λ) of B. tabaci increased significantly with dual infection as compared with only B. tabaci infestation. In contrast, B. tabaci pre-infestation reduced the longevity and oviposition days of DBM, but the population parameters r, R0, and λ did not vary significantly compared with only DBM infestation. Thus, co-infestation of B. tabaci and DBM was beneficial to the performance of the B. tabaci population. The present findings highlight that B. tabaci has become a dominant competitor when mixing with DBM on the same host plant.

Effects of periodically repeated high-temperature exposure on the immediate and subsequent fitness of different developmental stages of Propylaea japonica.

BACKGROUND: Repeated extreme high temperature occurs frequently in summer. Propylaea japonica is a predominant predator in South-East Asia and has been considered as a successful natural enemy to control aphids. However, how repeated extreme high temperature affects the fitness of P. japonica remains unclear. This study evaluated the immediate and subsequent fitness of P. japonica when egg, larva, pupa, and adult were exposed to repeated high temperatures (39, 41, or 43 °C for 3 h exposure duration per day) during several days. RESULTS: The effect of repeated high temperatures on P. japonica fitness was stage-specific: the egg stage was the most sensitive, the larval and pupal stages were moderately resistant and the adult stage was the most resistant to heat. Repeated high temperatures extended the immature developmental time and decreased the sex ratio of eggs treated with these temperatures, compared to control eggs. A temperature of 39 °C had no significant effect on the pre-oviposition period, oviposition period, fecundity (except stress pupa), or longevity compared with the control, but negative carry-over effects above 39 °C on subsequent stages were found. CONCLUSION: Repeated high temperature for consecutive days not only had a significant effect on the immediate survival and developmental time, but also had deleterious effects on the subsequent development and performance of P. japonica. The present study provides valuable information for understanding and utilizing P. japonica to control aphids in challenging environments. © 2022 Society of Chemical Industry.

A new pest management strategy: transforming a non-host plant into a dead-end trap crop for the diamondback moth Plutella xylostella L.

BACKGROUND: The use of trap crops can reduce the egg production of female Plutella xylostella in cruciferous vegetables and is an effective method for controlling this pest. To date, most of the trap plants that have been studied are cruciferous plants containing high concentrations of glucosinolates, which are more attractive to P. xylostella female adults. However, the application of these trap plants also has some limitations. Studies have shown that aqueous extracts of cruciferous plants can attract P. xylostella to lay eggs. In this study, we utilized the extract of Chinese kale to treat a non-host plant, the faba bean, and evaluated the possibility of using it as a dead-end trap plant for P. xylostella control. RESULTS: Plutella xylostella females laid significantly more eggs on faba beans that had been sprayed with the extract of Chinese kale rather than on Chinese kale itself. The first instar larvae of P. xylostella failed to survive on faba beans. Notably, the faba beans with the Chinese kale extract had the strongest attraction effect on P. xylostella females when placed 3 m away from the Chinese kale. Moreover, this attraction effect of faba beans on P. xylostella for oviposition lasted for up to 15 days. CONCLUSION: Faba bean plants sprayed with the aqueous extract of Chinese kale represent a potential dead-end trap plant for P. xylostella adults and their oviposition while being invariably deadly for their offspring. The present study provides a new proof of concept of using a non-cruciferous trap plant for P. xylostella management.

[Drug Knowledge of Middle School Students in HIV-prone Areas of Liangshan].

OBJECTIVE: To investigate drug knowledge of middle school students in HIV prone areas in Liangshan of Sichuan Province. METHODS: Students were randomly selected from the middle schools located in the HIV prone areas in Liangshan. A questionnaire survey was conducted. Drug knowledge of the respondents and associated factors were analyzed. RESULTS: Of the 10 749 respondents,10.1% had wrong knowledge about drugs. The respondents of male gender and minority ethnicity in the region and those who were in a lower grade,had poor academic records,more sisters,and a schoolmate taking drugs,and lived in a family with HIV infected member were more likely to had poor drug knowledge. By contrast,the respondents who had a peasant father,lived with both parents,resided in a city or township,self-rated in the middle and low 1/3 of wealth,lived in a community with >50% school attendance,and had a family member taking drugs were less likely to have wrong drug knowledge. CONCLUSION: Middle school students in the HIV prone areas in Liangshan have poor drug knowledge. Socioeconomic factors influence the drug knowledge of students,which require systematic interventions.

[Smoking in Middle School Students in Priority Areas for HIV Control in Liangshan].

OBJECTIVE: To determine the prevalence and determinants of smoking in middle school students in priority areas for HIV control in Liangshan of Sichuan Province. METHODS: Students were randomly selected in all of the schools located in the priority areas for HIV control in Liangshan. A questionnaire survey was conducted,collecting data in relation to socio-demographic characteristics of the participants,their smoking behavior,drug abuse in family members,and HIV infections in family members. Risk factors associated with smoking were identified using univariate and multivariate statistical analyses. RESULTS: About 21.3% of respondents were smoking at the time of survey; 33.4% attempted smoking; 5% were heavy smokers; and 16.8% started smoking before 13 years old. The Logistic regression analysis identified male gender,senior high school students,poor academic records,low household income,rural residency,family drug abuse and HIV infections as predictors of attempted smoking. Male gender,minority ethnicity,average academic records,broken family,medium and high household income,family drug abuse and HIV infections were identified as predictors of smoking. Male gender,senior high school students,low or medium academic records,rural residency,and family drug abuse were identified as predictors of heavy smoking. Male gender,broken family,average academic records,medium or high household income,family drug abuse and HIV infections were associated with smoking before thirteen. CONCLUSION: Smoking rate in middle school students in the priority areas for HIV control in Liangshan is high. They start smoking at a young age. School smoking control programs should place priorities on those who are in the groups of boys,minority ethnicity,senior high school students,rural residency,poor academic records,and those with family drug abuse and HIV infections.

The Potential Coordination of the Heat-Shock Proteins and Antioxidant Enzyme Genes of Aphidius gifuensis in Response to Thermal Stress.

Aphidius gifuensis is one of the most important aphid natural enemies and has been successfully used to control Myzys persicae and other aphid species. High temperature in summer is one of the key barriers for the application of A. gifuensis in the field and greenhouse. In this work, we investigated the biological performance of A. gifuensis and the response of heat-shock proteins and antioxidant enzymes under high temperature. The results showed that A. gifuensis could not survive at 40°C and female exhibited a higher survival in 35°C. Furthermore, the short term exposure to high temperature negatively affected the performance of A. gifuensis especially parasitism efficiency. Under short-term heating, the expression of AgifsHSP, Agifl(2)efl, AgifHSP70, AgifHSP70-4 and AgifHSP90 showed an increased trend, whereas AgifHSP10 initially increased and then decreased. In 35°C, the expressions of Agifl(2)efl, AgifHSP70-4 and AgifHSP90 in female were higher than those in male, whereas the expression of AgifHSP70 exhibited an opposite trend. Besides the HSPs, we also quantified the expression levels of 11 antioxidant enzyme genes: AgifPOD, AgifSOD1, AgifSOD2, AgifSOD3, AgifCAT1, AgifCAT2, AgifGST1, AgifGST2, AgifGST3, AgifGST4 and AgifGST5. We found that the sex-specific expression of AgifSOD2, AgifSOD3, AgifPOD, AgifGST1 and AgifGST3 were highly consistent with sex-specific heat shock survival rates at 35°C. Furthermore, when the temperature was above 30°C, the activities of GST, SOD, CAT and POD were significantly increased; however, there was no significant difference of the CAT activity between the male and female at 35°C. Collectively, all of these results suggested that the protection of thermal damage is coordinated by HSPs and antioxidant enzymes in A. gifuensis. Based on the heat tolerance abilities of many aphid natural enemies, we also discussed an integrated application strategy of many aphid enemies in summer.