The migratory locust, Locusta migratoria manilensis, is an immensely destructive agricultural pest that forms a devastating and voracious gregarious phase. The fungal insect pathogen, Metarhizium acridum, is a specialized locust pathogen that has been used as a potent mycoinsecticide for locust control. Little, however, is known about locust immune tissue, i.e. fat body and hemocyte, responses to challenge by this fungus. RNA-seq (RNA sequencing) technology were applied to comparatively examine the different roles of locust fat body and hemocytes, the two major contributors to the insect immune response, in defense against M. acridum. According to the sequence identity to homologies of other species explored immune response genes, immune related unigenes were screened in all transcriptome wide range from locust and the differential expressed genes were identified in these two tissues, respectively. Analysis of differentially expressed locust genes revealed 4660 and 138 up-regulated, and 1647 and 23 down-regulated transcripts in the fat body and hemocytes, respectively after inoculation with M. acridum spores. GO (Gene Ontology) enrichment analysis showed membrane biogenesis related proteins and effector proteins significantly differentially expressed in hemocytes, while the expression of energy metabolism and development related transcripts were enriched in the fat body after fungal infection. A total of 470 immune related unigenes were identified, including members of the three major insect immune pathways, i.e. Toll, Imd (immune deficiency) and JAK/STAT (janus kinase/signal transduction and activator of transcription). Of these, 58 and three were differentially expressed in the insect fat body or hemocytes after infection, respectively. Of differential expressed transcripts post challenge, 43 were found in both the fat body and hemocytes, including the LmLys4 lysozyme, representing a microbial cell wall targeting enzyme. These data indicate that locust fat body and hemocytes adopt different strategies in response to M. acridum infection. Fat body gene expression after M. acridum challenge appears to function mainly through activation of innate immune related genes, energy metabolism and development related genes. Hemocyte responses attempt to limit fungal infection primarily through regulation of membrane related genes and activation of cellular immune responses and release of humoral immune factors.

Background: The fall armyworm (FAW), Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is an aggressive pest species that causes severe economic losses in outbreak regions. Use of FAW natural enemies, particularly native parasitoids, has been suggested as a promising control strategy. Campoletis chlorideae Uchida (Hymenoptera: Ichneumonidae) is a solitary ichneumonid larval endoparasitoid with a broad host range that includes S. frugiperda. However, its parasitism rate, developmental stages, and population dynamics during parasitization of S. frugiperda remain unclear. A field survey was conducted to determine the emergence rate and sex ratio of C. chlorideae, evaluated the biological control performance, and investigated the production potential of it on the individually reared and group-reared S. frugiperda through age-stage, two-sex life tables, respectively. Results: The results showed that C. chlorideae parasitizing individually reared FAW resulted for the parasitoid in a lifetime total fecundity (F) of 301.5 ± 16.4 eggs/female, a net reproduction rate (R₀) of 62.03 ± 9.07 adult females/female, an overall life span of females of 28.3 ± 0.52 days, and an intrinsic rate of increase (r) of 0.1946 ± 0.0076 day⁻¹. In contrast, the parameters of F, R₀, overall life span of females, and r were 87.71 ± 6.32 pupae/female, 6.02 ± 1.61 adult females/female, 25.21 ± 0.79 days, and 0.0918 ± 0.0148 day⁻¹ in group-reared S. frugiperda. Conclusions: This study suggests that C. chlorideae has a promising biological control potential against S. frugiperda. Future research should focus on developing methods to increase the production of C. chlorideae.

Editorial: Insect behavioral adaptations and immune responses to stress