Larval Frass Research Articles

Impacts of black soldier fly, Hermetia illucens, larval frass on the emergence and seedling vigor of three vegetable crop species

Abstract The waste material from rearing black soldier fly, Hermetia illucens (L.), (Diptera: Stratiomyidae), larvae (BSFL), frass, could serve as a partial replacement for fertilizer or growing media, such as peat. Studies have shown that depending on the crop life cycle, long or short, the incorporation of frass can have positive impacts on vegetable growth. Investigating the earlier stages of growth, such as emergence, can provide more information on the acute impacts of insect frass on plant production. Two greenhouse studies were designed to investigate the use of frass in vegetable production at the seedling stage: BSFL frass as a partial replacement for peat in a growth germination medium and BSFL frass as a fertility replacement in a growth germination medium. Tomato, lettuce, and arugula seeds were grown in a standard control growing media, a growing media amended with frass to partially replace peat, and a growing media with frass applications to substitute the fertility source. In all treatments and varieties, the control growing media produced better or comparable results to the treatments. As a peat replacement, the two tomato varieties, lettuce, and arugula seedlings grown in frass had comparable seedling vigour and days to emergence to those grown in the control. As a fertility replacement, seedlings grown in frass had significantly lower percent emergence in all four cultivars when compared to the control. The tomato varieties also had significantly lower seedling vigour in the BSFL fertility treatments than the control. Depending on crop and growing media composition, the impacts of frass on early plant development vary. The adoption of frass into growing practices should include preliminary tests for nutrient composition and microbial contamination.

Evaluation of the Fertilizer Potential of Black Soldier Fly Larval Frass Obtained by the Processing of Multiple Organic Wastes in Agriculture in Cameroon: Effects on Plant Growth Parameters and Maize Kernel Nutrient Composition

The growing utilization of inorganic fertilizers results in the depletion of a minimal quantity of essential elements, including phosphorus, nitrogen, and potassium. The residual fraction is discharged into the environment as organic waste, posing a threat to the ecosystem.The black soldier fly larvae (BSFL) have been acknowledged as a solution for the increasing problem of organic waste. BSFL provides numerous benefits, including their current use of waste material, known as frass, as an organic fertilizer. The aim of this study is to examine the fertilizing properties of frass and its effects on plant growth parameters and nutrient concentration in maize kernels when consumed. This will be compared to other cultivation methods including synthetic fertilizers, conventional compost, and no compost. Following a 90-day timeframe, a comprehensive analysis was performed to assess the growth characteristics and nutrient composition within the kennels. The results of this study indicate that frass positively affects plant growth and has a favorable blend of nutrients, as previously demonstrated by studies investigating the nutrient levels in maize. This study showcased the capacity of utilizing frass as a carrier to boost agricultural output and enhance the accessibility of particular nutrients in plants. Further investigation is required to substantiate these conclusions. The widespread use of black soldier fly larvae in the agricultural sector in poor countries, particularly in Sub-Saharan Africa, has the capacity to have a beneficial effect on integrated sustainable agriculture and the achievement of Sustainable Development Goals 2, 11, and 12.

Effect of black soldier fly larval frass on the soil microbial communities, nutrient uptake and yield of radish (Raphanus sativus L.)

Effect of black soldier fly larval frass on the soil microbial communities, nutrient uptake and yield of radish (Raphanus sativus L.)

Impact of Black Soldier Fly Larval Frass on Growth and Yield of Cluster Bean (Cyamopsis tetragonoloba L.)

Hermetia illucens L., commonly known as the Black Soldier Fly (BSF), has garnered global attention for its role in insect farming due to its efficient conversion of organic waste into nutrient-rich larval biomass, with frass as a primary byproduct. This study aimed to explore the potential of BSF larval frass (BSFF) as an organic fertilizer for agricultural production, especially evaluating its performance compared to vermicompost on cluster bean growth and yield under field conditions during rabi season at Rajendranagar, Hyderabad. Using a completely randomized block design with eight treatments, various growth parameters such as plant height, number of branches plant-1 and dry matter production, along with yield attributes including number of clusters plant-1, number of pods cluster-1, number of pods plant-1, pod weight (g), pod yield plant-1 and yield (t ha-1) were assessed. Significant differences were observed among treatments, the highest growth and yield parameters were recorded in application of 25 % N through BSF frass + 75 % RDN (T5) and it was on par with 25 % N through vermicompost + 75 % RDN (T6), 50 % N through BSF frass + 50 % RDN (T7), 50 % N through vermicompost + 50 % RDN (T8) and RDF (T2) compared to 100 % N through BSF frass (T3), 100 % N through vermicompost (T4) and control (T1).These treatments resulted in yield increase of 35.7 % (T5), 24.7 % (T6), 23.4 % (T7), 22 %(T8) and 24.36 % (T2) respectively, compared to the control. These findings indicated that BSF larval frass holds promise as a sustainable alternative to vermicompost for enhancing cluster bean production, offering potential benefits for agricultural sustainability and organic waste management.

Recirculating frass from food waste bioconversion using black soldier fly larvae: Impacts on process efficiency and product quality

Biowaste generation is increasing worldwide and inadequate disposal has strong negative impacts on food systems and ecosystems. Biodigestion of biowaste using black soldier fly (Hermetia illucens) larvae (BSFL) generates valuable by-products such as animal feed (larval biomass) and organic fertiliser (frass). However, the latter is typically unstable immediately after waste conversion and is thus unsafe for use as a fertilizer in terms of maturity. This study evaluated recirculation of frass within bioconversion of post-consumer food waste (FW) as a dietary component for BSFL to improve the quality of the subsequent frass obtained. Frass was introduced at increasing inclusion levels replacing food waste (2.5–100% on wet-weight basis) as part of the larvae's feeding substrate. Bioconversion efficiency and material reduction were significantly reduced by frass inclusion, while larval yield per experimental unit remained unchanged. When considering only the waste component in the larval diet, larval yield (dry-weight basis) ranged between 207 (0% frass inclusion) and 403 (40% frass inclusion) kg tonne FW−1, thus increasing by up to 94% at higher frass inclusion. With increasing dietary inclusion rate of frass from 0% to 100%, crude protein content of larval biomass increased by 41%, while fat content was reduced by 32%. The recirculated frass (obtained after including frass in the larval diet) had elevated concentrations of P, K, S, Na and B and around 6% lower organic matter content, demonstrating a higher degree of decomposition. Frass inclusion in the larval diet generated recirculated frass that were more stable and mature, as indicated by self-heating capacity, CO2 and NH3 volatilisation, seed germination bioassays and other parameters. It was concluded that frass recirculation improves waste bioconversion efficiency in relation to food waste unit, as well as larval biomass and frass quality, ensuring safer use as a fertilizer.

Eco-friendly pH-responsive iron-doped insect larval frass extract as a hexaconazole nano-delivery system for controlling fungal disease and promoting crop growth

Developing environmentally friendly pesticides and improving pesticide utilization efficiency are urgent needs for modern agriculture. Herein, a pH-responsive biodegradable dual pesticide-fertilizer was fabricated using extracts from naturally occurring Protaetia brevitarsis larval frass (PBLF) material. Iron ions (Fe3+) were integrated as metal nodes into PBLF, and hexaconazole (Hex), a triazole fungicide, was encapsulated in Fe-PBLF with a loading rate of 22.93 %. Hex@Fe-PBLF nanoparticles (NPs) presented a sphere-like construction with a hydrated size of 715.3 ± 5.0 nm and exhibited acid-responsive controlled release behavior, gradually self-degrading in acidic environments within 120 h. The NPs showed good foliar adhesion and were effectively absorbed and translocated by pathogenic fungal mycelium and the rice seedling. Compared with Hex Technical control (TC), the control effects of Hex@Fe-PBLF against Rhizoctonia solani (R. solani) and Botrytis cinerea (B. cinerea) increased by 9.9 % and 12.73 %, respectively, after 7 days. This naturally sourced nanocarrier not only promoted the growth of rice seedlings as a fertilizer but also enhanced their stress resistance. The low mobility of Hex@Fe-PBLF NPs in soil effectively reduced environmental risks. The excellent biosafety of the Fe-PBLF nanocarrier was further evaluated. Overall, this environmental-friendly multifunctional nano pesticide-fertilizer has promising application potential in agriculture.

Impacts of black soldier fly, Hermetia illucens, larval frass on lettuce and arugula production

Impacts of black soldier fly, Hermetia illucens, larval frass on lettuce and arugula production

Larval Frass of Hermetia illucens as Organic Fertilizer: Composition and Beneficial Effects on Different Crops.

Hermetia illucens has received a lot of attention as its larval stage can grow on organic substrates, even those that are decomposing. Black soldier fly breeding provides a variety of valuable products, including frass, a mixture of larval excrements, larval exuviae, and leftover feedstock, that can be used as a fertilizer in agriculture. Organic fertilizers, such as frass, bringing beneficial bacteria and organic materials into the soil, improves its health and fertility. This comprehensive review delves into a comparative analysis of frass derived from larvae fed on different substrates. The composition of micro- and macro-nutrients, pH levels, organic matter content, electrical conductivity, moisture levels, and the proportion of dry matter are under consideration. The effect of different feeding substrates on the presence of potentially beneficial bacteria for plant growth within the frass is also reported. A critical feature examined in this review is the post-application beneficial impacts of frass on crops, highlighting the agricultural benefits and drawbacks of introducing Hermetia illucens frass into cultivation operations. One notable feature of this review is the categorization of the crops studied into distinct groups, which is useful to simplify comparisons in future research.

Evaluation of Virgibacillus dokdonensis MCCC 1A00493 as a biological control agent and microbial organic fertilizer against root-knot nematodes

Root-knot nematodes (RKNs) can result in severe losses to crop production and economies. Virgibacillus dokdonensis MCCC 1A00493, a deep-sea bacterium, has demonstrated potent antagonistic effects against Meloidogyne incognita in vitro. However, the control efficacy under greenhouse and field conditions remains unclear. In this study, we investigated the nematicidal effect of MCCC 1A00493 fermentation liquid and its synergism with black soldier fly (BSF) larval frass organic fertilizer both in greenhouse and field experiments. MCCC 1A00493 fermentation liquid demonstrated a significant control efficacy on RKNs both in greenhouse and field experiments, with the highest control efficacy reaching 68.97 % and 74.87 %, respectively. Meanwhile, the synergistic effects of MCCC 1A00493 and BSF larvae frass organic fertilizer was investigated by adding 10 % suspension (1 × 109 CFU/mL) of MCCC 1A00493 into 71.51 kg of chicken manure organic fertilizer produced by co-conversion of BSF larvae and Bacillus subtilis BSF-CL. It was noted that MCCC 1A00493 microbial organic fertilizer reduced disease incidence of RKNs significantly both in greenhouse and field experiments, with the root gall index decreasing by 51.75 % and 63.22 %, respectively. MCCC 1A00493 fermentation liquid and microbial organic fertilizer demonstrated a control efficacy on RKNs exceeded commercial nematicide avermectin and commercial bio-organic fertilizer, respectively. In addition, MCCC 1A00493 fermentation liquid and microbial organic fertilizer had positive effects on the growth of tomato plants. These findings confirmed that V.dokdonensis MCCC 1A00493 as a biological control agent and microbial organic fertilizer have significant effect on RKNs and can be used as potential biocontrol preparations.

Effect of Protaetia brevitarsis larval frass fertilizer on the growth of ginseng sprout (Panax ginseng) in commercial potting soil

Effect of Protaetia brevitarsis larval frass fertilizer on the growth of ginseng sprout (Panax ginseng) in commercial potting soil

Functional and Compositional Changes in Sirex noctilio Gut Microbiome in Different Habitats: Unraveling the Complexity of Invasive Adaptation.

The mutualistic symbiosis relationship between the gut microbiome and their insect hosts has attracted much scientific attention. The native woodwasp, Sirex nitobei, and the invasive European woodwasp, Sirex noctilio, are two pests that infest pines in northeastern China. Following its encounter with the native species, however, there is a lack of research on whether the gut microbiome of S. noctilio changed, what causes contributed to these alterations, and whether these changes were more conducive to invasive colonization. We used high-throughput and metatranscriptomic sequencing to investigate S. noctilio larval gut and frass from four sites where only S. noctilio and both two Sirex species and investigated the effects of environmental factors, biological interactions, and ecological processes on S. noctilio gut microbial community assembly. Amplicon sequencing of two Sirex species revealed differential patterns of bacterial and fungal composition and functional prediction. S. noctilio larval gut bacterial and fungal diversity was essentially higher in coexistence sites than in separate existence sites, and most of the larval gut bacterial and fungal community functional predictions were significantly different as well. Moreover, temperature and precipitation positively correlate with most of the highly abundant bacterial and fungal genera. Source-tracking analysis showed that S. noctilio larvae at coexistence sites remain dependent on adult gut transmission (vertical transmission) or recruitment to frass (horizontal transmission). Meanwhile, stochastic processes of drift and dispersal limitation also have important impacts on the assembly of S. noctilio larval gut microbiome, especially at coexistence sites. In summary, our results reveal the potential role of changes in S. noctilio larval gut microbiome in the successful colonization and better adaptation of the environment.

Germination Behavior and Geographical Information System-Based Phenotyping of Root Hairs to Evaluate the Effects of Different Sources of Black Soldier Fly (Hermetia illucens) Larval Frass on Herbaceous Crops.

Insect larval frass has been proposed as a fertilizer and amendment, but methods for testing its effects on plants are poorly developed and need standardization. We obtained different types of black soldier fly (Hermetia illucens) frass via the factorial combination of (a) two insect diets, as follows: G (Gainesville = 50% wheat bran, 30% alfalfa meal, 20% maize meal) and W (43% sheep whey + 57% seeds); (b) two frass thermal treatments: NT = untreated and T = treated at 70 °C for 1 h. We tested the effects on the germination of cress (Lepidium sativum L.) and wheat (Triticum durum Desf.) by applying 1:2 w:w water extracts at 0, 25, 50, 75 and 100% concentration. Standardizing frass water content before extraction affected chemical composition. Frass extracts showed high electrical conductivity (8.88 to 13.78 mS cm-1). The W diet was suppressive towards Escherichia coli and showed a lower content of nitrates (e.g., WNT 40% lower than GNT) and a concentration-dependent phytotoxic effect on germinating plants. At 25% concentration, germination indices of G were 4.5 to 40-fold those at 100%. Root and shoot length and root hair area were affected by diet and concentration of frass extracts (e.g., root and shoot length in cress at 25% were, respectively, 4.53 and 2 times higher than at 100%), whereas the effects of the thermal treatment were few or inconclusive. On barley (Hordeum vulgare L.) grown in micropots on a silty loam soil, root mass was reduced by 37% at high extract concentration. A quick procedure for root hair surface area was developed based on the geographic information system (GIS) and may provide a fast method for incorporating root hair phenotyping in frass evaluation. The results indicate that below-ground structures need to be addressed in research on frass effects. For this, phyotoxicity tests should encompass different extract dilutions, and frass water content should be standardized before extraction in the direction of canonical procedures to allow comparisons.

Parasitoid-induced changes in metabolic rate and feeding activity of the emerald ash borer (Coleoptera: Buprestidae): implications for biological control

Parasitoid-host interactions form the foundation of biological control strategies against many agriculture and forest insect pests. The emerald ash borer (EAB), Agrilus planipennis (Coleoptera: Buprestidae), is a serious invasive pest of ash (Fraxinus spp.) trees in North America. Tetrastichus planipennisi (Hymenoptera: Eulophidae) is a gregarious, koinobiont endoparasitoid, attacking late (3rd to 4th) instars of EAB larvae, which feed in the live phloem of ash trunks or branches, making serpentine-like galleries filled with larval frass. In the present study, we tested the hypothesis that T. planipennisi regulates the host metabolism and feeding activity to optimize its offspring development and fitness. We first compared the respiration rate of parasitized and unparasitized host larvae at different times after parasitism, and then measured feeding activity of both parasitized and unparasitized host larvae inside their feeding galleries. Although parasitized host larvae increased metabolic rate and feeding activity in the first few days of parasitism, T. planipennisi parasitism induced an overall reduction of the metabolic rate and decrease in feeding activity of parasitized host larvae over their development period. In addition, there was a negative relationship between feeding activity of parasitized hosts and brood sizes of the parasitoid progeny—i.e., the more parasitoid progeny a host larva received, the less feeding activity the host had. These findings suggest that T. planipennisi has limited ability to optimize its offspring development and fitness through regulations of the host metabolism and feeding activity and its parasitism reduces feeding damage of parasitized EAB larvae to infested ash trees.

An extract from the frass of swallowtail butterfly (Papilio machaon) larvae inhibits HCT116 colon cancer cell proliferation but not other cancer cell types

BackgroundThe frass of several herbivorous insect species has been utilised as natural medicines in Asia; however, the metabolite makeup and pharmaceutical activities of insect frass have yet to be investigated. Oligophagous Papilionidae insects utilise specific kinds of plants, and it has been suggested that the biochemicals from the plants may be metabolised by cytochrome P450 (CYP) in Papilionidae insects. In this study, we extracted the components of the frass of Papilio machaon larvae reared on Angelica keiskei, Oenanthe javanica or Foeniculum vulgare and examined the biological activity of each component. Then, we explored the expression of CYP genes in the midgut of P. machaon larvae and predicted the characteristics of their metabolic system.ResultsThe components that were extracted using hexane, chloroform or methanol were biochemically different between larval frass and the host plants on which the larvae had fed. Furthermore, a fraction obtained from the chloroform extract from frass of A. keiskei-fed larvae specifically inhibited the cell proliferation of the human colon cancer cell line HCT116, whereas fractions obtained from the chloroform extracts of O. javanica- or F. vulgare-fed larval frass did not affect HCT116 cell viability. The metabolites from the chloroform extract from frass of A. keiskei-fed larvae prevented cell proliferation and induced apoptosis in HCT116 cells. Next, we explored the metabolic enzyme candidates in A. keiskei-fed larvae by RNA-seq analysis. We found that the A. keiskei-fed larval midgut might have different characteristics from the O. javanica- or F. vulgare-fed larval metabolic systems, and we found that the CYP6B2 transcript was highly expressed in the A. keiskei-fed larval midgut.ConclusionsThese findings indicate that P. machaon metabolites might be useful as pharmaceutical agents against human colon cancer subtypes. Importantly, our findings show that it might be possible to use insect metabolic enzymes for the chemical structural conversion of plant-derived compounds with complex structures.

High-quality DNA isolation protocol for detection of Khapra beetle (Dermestidae: Trogoderma granarium Everts, 1898) in standard wheat germ trap.

Khapra beetle (Dermestidae: Trogoderma granarium Everts, 1898) is an internationally significant pest of grain crops and stored grain products. Wheat germ traps, routinely used in surveillance sampling of Khapra beetle provide feed-substrates used by the pest throughout its life cycle. However, Khapra beetle larvae, eggs and other traces of the pest, such as larval frass and exuviae, in wheat germ traps are difficult to sort and taxonomically identify. Additionally, high levels of polysaccharides in wheat germ can inhibit PCR based molecular detection of this pest captured in the traps. We have developed a sensitive and low-cost protocol for extracting trace levels of Khapra beetle DNA from an entire wheat germ trap. Overnight digestion of entire trap contents in 6 mL of ATL buffer, followed by a 40min lysis step was optimal for DNA extraction. Paired with reported qPCR assays, this protocol allows the detection of a few hairs of T. granarium in a typical 2-gram wheat germ trap. This DNA extraction protocol makes it possible to perform a more rapid identification of the pest following wheat germ sample collection. The protocol has potential to improve international efforts for Khapra beetle surveillance.

A biochemical analysis of Black Soldier fly (Hermetia illucens) larval frass plant growth promoting activity.

Black Soldier fly (Hermetia illucens) larval (BSFL) frass was examined for its nutrient nitrogen, phosphate and potassium (N:P205:K2O), phytohormone and biogenic amine content, its plant growth promoting activity, and screened to test the hypothesis that bacteria characteristic of the genus Enterococcus (present in the biome of decaying catering waste and the larval gut) are excreted by BSFL in their frass. Frass plant growth promoting activity was measured by comparing the growth of winter wheat berry (Triticum aestivum) in frass treated soil to that of untreated (control) soil. The N:P205:K2O percent dry matter average, biogenic amine and phytohormone content of frass was determined by standard soil analysis, HPLC and HPLC/GC-MS methodologies, respectively. All were at too low of concentrations to account for its plant growth promoting activity. Frass added to soil induced a 11% increase in aerial mass and shoot length in treated plants over controls. Numerous colonies of Enterococci growing out on BEA (bile-esculin-agar) plates were detected in frass collected directly from larvae confirming the hypothesis that viable Enteroccoci are passing from the larval gut into their frass. Since a number of rhizobacteria, including Enterococci, have previously been identified as part of the larval gut biome, the passage of Enterococci from the larval gut into frass in the face of only trace N:P205:K2O percent dry matter averages, biogenic amine and phytohormone content is consistent with the hypothesis that Enterococci exhibiting rhizobacterial activity have a role in conferring to frass its plant growth promoting activity.

Host’s genetic background determines the outcome of reciprocal faecal transplantation on life-history traits and microbiome composition

BackgroundMicrobes play a role in their host's fundamental ecological, chemical, and physiological processes. Host life-history traits from defence to growth are therefore determined not only by the abiotic environment and genotype but also by microbiota composition. However, the relative importance and interactive effects of these factors may vary between organisms. Such connections remain particularly elusive in Lepidoptera, which have been argued to lack a permanent microbiome and have microbiota primarily determined by their diet and environment. We tested the microbiome specificity and its influence on life-history traits of two colour genotypes of the wood tiger moth (Arctia plantaginis) that differ in several traits, including growth. All individuals were grown in the laboratory for several generations with standardized conditions. We analyzed the bacterial community of the genotypes before and after a reciprocal frass (i.e., larval faeces) transplantation and followed growth rate, pupal mass, and the production of defensive secretion.ResultsAfter transplantation, the fast-growing genotype grew significantly slower compared to the controls, but the slow-growing genotype did not change its growth rate. The frass transplant also increased the volume of defensive secretions in the fast-growing genotype but did not affect pupal mass. Overall, the fast-growing genotype appeared more susceptible to the transplantation than the slow-growing genotype. Microbiome differences between the genotypes strongly suggest genotype-based selective filtering of bacteria from the diet and environment. A novel cluster of insect-associated Erysipelotrichaceae was exclusive to the fast-growing genotype, and specific Enterococcaceae were characteristic to the slow-growing genotype. These Enterococcaceae became more prevalent in the fast-growing genotype after the transplant, which suggests that a slower growth rate is potentially related to their presence.ConclusionsWe show that reciprocal frass transplantation can reverse some genotype-specific life-history traits in a lepidopteran host. The results indicate that genotype-specific selective filtering can fine-tune the bacterial community at specific life stages and tissues like the larval frass, even against a background of a highly variable community with stochastic assembly. Altogether, our findings suggest that the host's genotype can influence its susceptibility to being colonized by microbiota, impacting key life-history traits.

Alteration of Manure Antibiotic Resistance Genes via Soil Fauna Is Associated with the Intestinal Microbiome.

ABSTRACTLivestock wastes contain high levels of antibiotic resistance genes (ARGs) and a variety of human-related pathogens. Bioconversion of livestock manure using larvae of the beetle Protaetia brevitarsis is an effective technique for waste reduction and value creation; however, the fate of manure ARGs during gut passage and interaction with the gut microbiome of P. brevitarsis remains unclear. To investigate this, we fed P. brevitarsis with dry chicken manure for 6 days and measured bacterial community dynamics and ARG abundance and diversity along the P. brevitarsis gut tract using high-throughput quantitative PCR and metagenomics approaches. The diversity of ARGs was significantly lower in larval midgut, hindgut, and frass than in raw chicken manure, and around 80% of pathogenicity-related genes (PRGs) exhibited reduced abundance. Network analysis demonstrated that Bacteroidetes and Firmicutes were the key bacterial phyla associated with ARG reduction. Metagenomic analysis further indicated that ARGs, mobile genetic elements (MGEs), and PRGs were simultaneously attenuated in the hindgut, implicating a decreased likelihood for horizontal gene transfer (HGT) of ARGs among bacteria and pathogens during manure bioconversion. Our findings demonstrated that the attenuation of ARGs is strongly associated with the variation of the gut microbiome of P. brevitarsis, providing insights into mechanisms of risk mitigation of ARG dissemination during manure bioconversion.IMPORTANCE Saprophagous fauna like the oriental edible beetle (P. brevitarsis) plays a fundamental role in converting organic wastes into biofertilizer. Accumulating evidence has shown that soil fauna can reduce the abundance of ARGs, although the underlying mechanism of ARG reduction is still unclear. In our previous research, we found a large reduction of ARGs in vegetable roots and leaves from frass compared with raw manure, providing a promising biofertilizer for soil-vegetable systems. Therefore, in this study, temporal dynamic changes in the microbiomes of the donor (chicken manure) and host (P. brevitarsis) were investigated, and we found a close association between the gut microbiome and the alteration of ARGs. These results shed new light on how the insect gut microbiome can mitigate manure-borne ARGs and provide insights into the bioconversion process via a typical member of the saprophagous fauna, P. brevitarsis.

Comparison on the effectiveness of Fourier transform infrared (FT-IR) and attenuated total reflection Fourier transform infrared (ATR-FT-IR) in characterizing plastics biodegradation by insect larvae

The discovery that insect larvae can feed on foam plastics provided new exploration ideas and potential for plastic wastes biodegradation. In previous studies, both attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FT-IR) and conventional FT-IR have been used but no comparison has been done to evaluate the difference of effectiveness for the characterization of oxidization and biodegradation of plastics by insect larvae. To address this, foam plastics of polystyrene, polyurethane and polyethylene, as well as the frass of plastics-fed superworms Zophobas atratus were characterized using both FT-IR and ATR-FT-IR, and the differences were compared. For FT-IR, spectra were found to vary due to the difference in shape and thickness of the samples, as well as the moisture absorption of KBr. For ATR-FT-IR, although tests could be performed directly without pretreatment, the reflection with short wavelength could not deeply penetrate into the frass samples. Since the composition of plastics-fed larval frass is more complex than the original plastics, the spectra of FT-IR and ATR-FT-IR were observed significantly different. Therefore, the ATR-FT-IR was more effective in monitoring functional groups of original plastics, and be recommended to employ in combination with FT-IR for a more comprehensive characterization of plastics-fed larval frass in future studies.

Colorado potato beetle exploits frass-associated bacteria to suppress defense responses in potato plants.

Colorado potato beetle (CPB; Leptinotarsa decemlineata) is a destructive quarantine pest that develops broad physiological adaptations to potato plants. During feeding, CPB deposits a copious amount of wet frass onto the surface of leaves and stems that remains in place for long periods. Insect behaviors such as feeding, crawling and oviposition are able to mediate plant defenses. However, the specific role of CPB defecation-associated cues in manipulating plant defenses remains unclear. CPB larval frass significantly suppressed potato polyphenol oxidase activity and enhanced larval growth on treated potato plants. The incorporation of antibiotics into larval frass triggered higher jasmonic acid (JA)-regulated defense responses in potato plants compared with antibiotic-free frass. Four bacterial symbionts belonging to the genera Acinetobacter, Citrobacter, Enterobacter and Pantoea were isolated from larval frass and suppressed plant defenses. After reinoculation of these bacteria into axenic larvae, Acinetobacter and Citrobacter were found to be highly abundant in the frass, whereas Enterobacter and Pantoea were less abundant probably due to the negative effect of potato steroidal glycoalkaloids (SGA) such as α-solanine. Furthermore, direct application of Acinetobacter and Citrobacter to wounded potato plants significantly inhibited the expression of genes associated with the JA-mediated defense signaling pathway and SGA biosynthesis. Our findings demonstrate that CPB exploits frass-associated bacteria as a deceptive strategy of plant defense suppression, adding an interesting dimension to our understanding of how CPB successfully specializes on potato plants. © 2022 Society of Chemical Industry.