Yonghui Xie

The tobacco cutworm, Spodoptera litura F. (Lepidoptera: Noctuidae), is a polyphagous pest that causes enormous losses in tobacco production as it develops resistance to pesticides in China. Telenomus remus N. (Hymenoptera: Scelionidae) is an effective egg parasitoid for the genus Spodoptera. However, little is known about the volatile compounds that attract the parasitoid. In the present study, we investigated the response of T. remus to volatiles released from various sources, including Spodoptera litura egg masses, healthy tobacco plants, plants with manually introduced eggs, and plants with natural oviposition. The chemical profiles of the crude extracts were identified using gas chromatography–mass spectrometry (GC–MS), and the behavioral assay was performed using a Y‐tube olfactometer. Naïve and experienced T. remus showed significant attraction to crude extracts of S. litura egg masses and to oviposition‐induced plant volatiles (OIPVs). In subsequent experiments, different concentrations and combinations of the synthetic volatiles obtained from these crude extracts were tested. Notably, the binary and ternary mixtures showed significant attraction, where the binary combination of linalool (L) with tetracosane (T) and linalool (L) with cis‐3‐hexenyl acetate (C) was strongly attractive. These results underscore the potential of using synthetic volatile dispensers, particularly binary combinations with precise doses, to enhance retention of T. remus and improve the efficacy of the biological control program.

Successful biological control requires accurate knowledge of the host preference of the released parasitoid. Telenomus remus Nixon (1973) is an effective parasitoid of Spodoptera frugiperda (J.E. Smith) in many regions, but S. frugiperda is not ideal for mass rearing due to cannibalism and high feeding costs. This study evaluated the efficacy of T. remus by assessing parasitization and emergence rates on eggs of S. frugiperda and Spodoptera litura (Fabricius). Host preference was tested through choice and non-choice experiments using parasitoids reared on both hosts, and various host-parasitoid ratios were tested to assess density-dependent parasitism. Results showed that T. remus had higher parasitism and emergence rates on S. litura eggs, regardless of the rearing host. The highest parasitism was observed on S. litura (94.63%) from T. remus reared on S. litura eggs and the highest emergence rates was also on S. litura eggs from T. remus reared on S. frugiperda (88.03%). The lowest emergence rate (52.29%) was observed on S. frugiperda eggs under no-choice conditions. Parasitoids reared on S. frugiperda achieved the highest parasitism on S. litura eggs (98.11%) in host-parasitoid ratio tests, while the lowest emergence rate (55.02%) occurred when reared and tested on S. frugiperda. These results suggest that S. litura is a more suitable host for mass rearing T. remus, enhancing its potential as a biological control agent in the field.

The MC4-2 bacterium strain was isolated and purified from the Periplaneta americana intestine as a biocontrol agent with good antagonistic effect against the pathogens of a soil-borne disease called tobacco black shank. The MC4-2 strain was found to have good broad-spectrum inhibition by plate stand-off test. Based on 16S rRNA and gyrB genes, ANI analysis, and other comparative genomics methods, it was determined that the MC4-2 strain was Bacillus subtilis. The complete genome sequence showed that the genome size was 4,076,630bp, the average GC content was 43.78, and the total number of CDSs was 4,207. Genomic prediction analysis revealed that a total of 145 genes were annotated by the CAZy, containing mainly GH and CE enzymes that break down carbohydrates such as glucose, chitin, starch, and alginate, and a large number of enzymes involved in glycosylation were present. A total of ten secondary metabolite clusters were predicted, six clusters of which were annotated as surfactin, bacillaene, fengycin, bacillibactin, subtilosin A, and bacilysin. The present investigation found the biological control mechanism of B. subtilis MC4-2, which provides a strong theoretical basis for the best use of this strain in biological control methods and provides a reference for the subsequent development of agents of this bacterium.

Background: The mass production of natural predators with prolonged shelf life is a prerequisite for their field application as pest control agents. The traditional methods used for the mass production ofSerangium japonicumrely heavily on the consistent supply of natural prey. This study explains the effects ofB. tabaci(natural prey) andC. cephalonicaeggs (alternative food) on life history and transcriptome profile ofS. japanicum.Methods: This study compares the effects ofB. tabaci(natural prey) andC. cephalonicaeggs (alternative food) on biology, reproduction, and predatory efficacy, and transcriptome profile ofS. japanicum.Results: This study revealed thatS. japonicumwas able to successfully complete its life cycle while feeding onB. tabaci(natural prey) andC. cephalonicaeggs (alternative food). TheC. cephalonicaeggs fedS. japonicumindividuals had longer developmental period and lower fecundity as compared to those feeding on whitefly but the survival rates (3rd instar nymphs, 4th instar nymphs and pupae) and predatory efficacy ofC. cephalonicaeggs fedS. japonicumindividuals were significantly similar to to those feeding on whitefly.Transcriptome analysis showed that when faced with dietary changes,S. japanicumcould successfully feed onC. cephalonicaeggs by regulating genes related to nutrient transport, metabolism, and detoxification. Moreover,S. japanicumdegraded excess cellular components through ribosomal autophagy and apoptosis, which provided sufficient materials and energy for survival and basic metabolism.Conclusion: Corcyra cephalonicaeggs can be used as an alternate host for the predator,Serangium japonicum,as the survival rates and predatory efficacy of the predator are similar to those feeding on the natural host (B.tabaci). When faced with dietary changes,S. japanicumcould successfully feed onC. cephalonicaeggs as revealed by upregulation of genes related to nutrient transport, metabolism, and detoxification. These findings are of great significance for studying the functional evolution ofS. japonicumin response to dietary changes.

The genus Ajothrips was erected for two new species from India (Bhatti 1967), although subsequently a third Indian species was added (Bhatti 1997). All three species have remained known only from females, although Mound (2009) recorded the presence of sternal pore plates in unspecified males of this genus. The purpose of this note is to record the type species, A. karma, from China, and to describe the unknown male. The systematic position of the genus has a confusing history. Considered by Bhatti (1967) as related to Scirtothrips, it was subsequently excluded from the Scirtothrips genus-group (Masumoto & Okajima 2007). However, more recent studies (Ng & Mound 2015; Lima & Mound 2016) have retained the systematic relationship proposed by Bhatti.