Starvation and Imidacloprid Exposure Influence Immune Response by Anoplophora glabripennis (Coleoptera: Cerambycidae) to a Fungal Pathogen

High Trunk Truncation as a Potential Sustainable Management Option for Asian Longhorned Beetle on Salix babylonica

The Asian longhorned beetle (ALB) causes substantial economic and ecological losses, thus, an environmentally friendly management strategy is needed. Here, we propose high trunk truncation (HTT), the removal of the above 200 cm portion of trees, as a sustainable management strategy to control ALB. To examine the hypothesis, an initial step involved the assessment of various biological characteristics of ALB. Subsequently, a controlled field experiment was carried out utilizing HTT. Finally, HTT was applied in two additional ALB infestation regions. The results of the study of the biological characteristics of ALB showed that 76.31-78.88% of frass holes and 85.08-87.93% of emergence holes were located on branches above 200 cm. Adults preferred to feed on branches 2-3 cm in diameter, ALB eggs were predominantly laid on 5 cm branches, and both were primarily located above 200 cm. These results revealed a correlation between the number of ALBs and the tree crown height. The controlled field experiment showed that the number of ALBs was significantly decreased when the HTT strategy was implemented: approximately 90% of frass holes and 95% of adults were eradicated by HTT compared with the control. Different field surveys involving HTT have shown similar results. These findings provide valuable insights into a sustainable and efficient management strategy for reducing the number of ALBs.

Tenuazonic acid alters immune and physiological reactions and susceptibility to pathogens in Galleria mellonella larvae

Tenuazonic acid (TeA) is synthesized by phytopathogenic and opportunistic fungi and is detected in a broad range of foods. This natural compound is of interest in terms of toxicity to animals, but its mechanisms of action on insects are poorly understood. We administered TeA orally at different concentrations (0.2-5.0 mg/[gram of a growth medium]) to the model insect Galleria mellonella, with subsequent estimation of physiological, histological, and immunological parameters in different tissues (midgut, fat body, and hemolymph). Susceptibility of the TeA-treated larvae to pathogenic microorganisms Beauveria bassiana and Bacillus thuringiensis was also analyzed. The feeding of TeA to the larvae led to a substation delay of larval growth, apoptosis-like changes in midgut cells, and an increase in midgut bacterial load. A decrease in activities of detoxification enzymes and downregulation of genes Nox, lysozyme, and cecropin in the midgut and/or hemocoel tissues were detected. By contrast, genes gloverin, gallerimycin, and galiomycin and phenoloxidase activity proved to be upregulated in the studied tissues. Hemocyte density did not change under the influence of TeA. TeA administration increased susceptibility of the larvae to B. bassiana but diminished their susceptibility to B. thuringiensis. The results indicate that TeA disturbs wax moth gut physiology and immunity and also exerts a systemic action on this insect. Mechanisms underlying the observed changes in wax moth susceptibility to the pathogens are discussed.

Microbial Control of Invasive Forest Pests with Entomopathogenic Fungi: A Review of the Current Situation

The health of the forestlands of the world is impacted by a number of insect pests and some of them cause significant damage with serious economic and environmental implications. Whether it is damage of the North American cypress aphid in South America and Africa, or the destruction of maple trees in North America by the Asian long horned beetle, invasive forest pests are a major problem in many parts of the world. Several studies explored microbial control opportunities of invasive forest pests with entomopathogenic bacteria, fungi, and viruses, and some are successfully utilized as a part of integrated forest pest management programs around the world. This manuscript discusses some invasive pests and the status of their microbial control around the world with entomopathogenic fungi.

Parasitoid envenomation alters the Galleria mellonella midgut microbiota and immunity, thereby promoting fungal infection

Gut bacteria influence the development of different pathologies caused by bacteria, fungi and parasitoids in insects. Wax moth larvae became more susceptible to fungal infections after envenomation by the ectoparasitoid Habrobracon hebetor. In addition, spontaneous bacterioses occurred more often in envenomated larvae. We analyzed alterations in the midgut microbiota and immunity of the wax moth in response to H. hebetor envenomation and topical fungal infection (Beauveria bassiana) alone or in combination using 16S rRNA sequencing, an analysis of cultivable bacteria and a qPCR analysis of immunity- and stress-related genes. Envenomation led to a predominance shift from enterococci to enterobacteria, an increase in CFUs and the upregulation of AMPs in wax moth midguts. Furthermore, mycosis nonsignificantly increased the abundance of enterobacteria and the expression of AMPs in the midgut. Combined treatment led to a significant increase in the abundance of Serratia and a greater upregulation of gloverin. The oral administration of predominant bacteria (Enterococcus faecalis, Enterobacter sp. and Serratia marcescens) to wax moth larvae synergistically increased fungal susceptibility. Thus, the activation of midgut immunity might prevent the bacterial decomposition of envenomated larvae, thus permitting the development of fungal infections. Moreover, changes in the midgut bacterial community may promote fungal killing.

Imidacloprid Pesticide Regulates Gynaikothrips uzeli (Thysanoptera: Phlaeothripidae) Host Choice Behavior and Immunity Against Lecanicillium lecanii (Hypocreales: Clavicipitaceae)

We attempted to develop an efficient management strategy against gall thrips (Gynaikothrips uzeli Zimmermann (Thysanoptera: Phlaeothripidae)) via the combined application of a systemic insecticide (imidacloprid) and an entomopathogenic fungus (Lecanicillium lecanii Zimmerman (Hypocreales: Clavicipitaceae)). The attraction of G. uzeli to Ficus microcarpa volatiles after imidacloprid treatment was weaker than for untreated plants, which could be due to modulation of volatile metabolite profiles by imidacloprid. The toxicity of L. lecanii against nymph and adult thrips was much higher for those that fed on plants treated with a 50% lethal concentration (LC50) of imidacloprid than for the controls. Phenoloxidase (PO) activity was significantly inhibited in treated G. uzeli, while hemocyte abundances were not different in treated and healthy individuals. Thus, imidacloprid impacted the PO-related humoral immunity of G. uzeli, but not their cellular immunity. Overall, F. microcarpa treated with imidacloprid at LC50 concentrations exhibited volatile profiles that decreased the attraction of G. uzeli and also indirectly increased the pathogenicity of L. lecanni by inhibiting the humoral immunity of gall thrips. The results reported here suggest that combined application of imidacloprid and L. lecanii could be used as a new integrated control strategy against gall thrips.