Summary Soil‐dwelling entomopathogenic nematodes ( EPN s) kill arthropod hosts by injecting their symbiotic bacteria into the host hemolymph and feed on the bacteria and the tissue of the dying host for several generations cycles until the arthropod cadaver is completely depleted. The EPN –bacteria–arthropod cadaver complex represents a rich energy source for the surrounding opportunistic soil fungal biota and other competitors. We hypothesized that EPN s need to protect their food source until depletion and that the EPN symbiotic bacteria produce volatile and non‐volatile exudations that deter different soil fungal groups in the soil. We isolated the symbiotic bacteria species ( Alcaligenes faecalis ) from the EPN Oscheius spp. and ran infectivity bioassays against entomopathogenic fungi ( EPF ) as well as against plant pathogenic fungi ( PPF ). We found that both volatile and non‐volatile symbiotic bacterial exudations had negative effects on both EPF and PPF . Such deterrent function on functionally different fungal strains suggests a common mode of action of A. faecalis bacterial exudates, which has the potential to influence the structure of soil microbial communities, and could be integrated into pest management programs for increasing crop protection against fungal pathogens.

In this study, we tested the utility of the mitochondrial gene cytochrome c oxidase subunit 1 (CO1) as the barcode region to deal with taxonomical problems of Polypedilum (Tripodura) non-biting midges (Diptera: Chironomidae). The 114 DNA barcodes representing 27 morphospecies are divided into 33 well separated clusters based on both Neighbor Joining and Maximum Likelihood methods. DNA barcodes revealed an 82% success rate in matching with morphospecies. The selected DNA barcode data support 37-64 operational taxonomic units (OTUs) based on the methods of Automatic Barcode Gap Discovery (ABGD) and Poisson Tree Process (PTP). Furthermore, a priori species based on consistent phenotypic variations were attested by molecular analysis, and a taxonomical misidentification of barcode sequences from GenBank was found. We could not observe a distinct barcode gap but an overlap ranged from 9-12%. Our results supported DNA barcoding as an ideal method to detect cryptic species, delimit sibling species, and associate different life stages in non-biting midges.

Spodoptera frugiperda invaded China in the end of 2018 and has caused severe damage to maize and other crops. Several S. frugiperda naturally parasitized by nematodes were observed in Hainan Province, China. The morphological characteristics based on the results of scanning electron microscopy indicated that the nematode belongs to the family Mermithidae. Additionally, coding sequences for the 18 S and 28 S rDNA were amplified from the nematode genome, and phylogenetic analysis revealed that the nematode belongs to Ovomermis sinensis, a known entomoparasitic nematode. Our finding is the first record that S. frugiperda was naturally parasitized by O. sinensis. The results of this study are of great significance for potential biological control of S. frugiperda by indigenous natural beneficial organisms, i.e. O. sinensis within an integrated pest management system.

Spodoptera litura is a notorious leaf feeding insect pest in the Asia-Pacific region and leads to a significant economic loss in vegetable and field crop production. Entomopathogenic nematodes (EPNs), lethal parasites of insects, are used as biocontrol agents. Yunnan Province in China is a well-known region due to its rich biodiversity. In the present study, a survey of EPNs using the Galleria-baiting technique was conducted in 2017 and 2018 throughout the entire Yunnan province. In total, 789 soil samples were collected from 232 sites, of which 75 samples were positive for EPNs. Phylogenetic analyses of ITS, D2D3 expansion region of the 28S rRNA gene, as well as mitochondrial cytochrome c oxidase subunit I (COI), were performed to identify isolated nematode species and evaluate their genetic diversity. In total, 13, 3, and 58 identified populations belong to Steinernema, Heterorhabditis, and Oscheius, respectively. The phylogenetic relationships of EPN species in the three genera were analyzed with the Neighbor-Joining method. The virulence of the trapped isolates in the genera of Steinernema, Heterorhabditis, and Oscheius against S. litura was evaluated. Ten new indigenous isolates from Steinernema and Heterorhabditis showed prominent virulence to S. litura within 48 hr which is equivalent to that of commercial EPNs populations. The present study provides background information on indigenous EPN resources for S. litura control in Asia-Pacific region.

Pythium myriotylum is a destructive soil-borne pathogen, which causes severe yield losses in many crops. The pathogen is a major economic issue for the production of ginger. Due to environmental and regulatory concerns, it is necessary to find biological alternatives to chemical pesticide for P. myriotylum control. In the present study, trans-cinnamic acid (TCA) and the fermentation broth of symbiotic bacteria from eight species of entomopathogenic nematodes alone and the combination of TCA with the fermentation broth of each symbiotic bacterium, were tested for their effects on mycelial growth and zoospore germination of P. myriotylum. Results showed that TCA significantly inhibited mycelial growth. Fermentation broths from seven of the eight strains of symbiotic bacteria directly inhibited mycelial growth, especially symbiotic bacteria isolated from Steinernema feltiae (SN strain) and S. riobrave (7-12 strain). Moreover, adding TCA significantly increased the extent of the inhibitory effect of mycelial growth by fermentation broths of seven tested bacteria except that associated with S. rarum. All bacteria fermentation broths showed inhibitory effects on zoospore germination. However, TCA alone did not show an apparent inhibitory effect on zoospore germination as it did on mycelial growth. Antimicrobial effects on mycelial growth and zoospore germination were proportional to the concentration of symbiotic bacteria isolated from S. feltiae (SN strain). This research provides new options for biorational control of P. myriotylum using TCA and symbiotic bacteria of entomopathogenic nematodes and will facilitate the sustainable production of ginger and other crops affected by this oomycete pathogens disease.