New publication: Lopes et al. (2026) Plant Growth Regul, in press

In this study, we show that black soldier fly larvae frass is not only a fertilizer but also a rich source of bioactive plant compounds, including multiple phytohormone classes such as cytokinins, auxins, ABA, salicylates, indoleamines and an ethylene precursor, detected at nano– to picomolar levels. Comparing fresh frass from one food-waste bioconversion cycle with frass that was recirculated through a second bioconversion cycle, we observed that recirculation reduced humic and fulvic acids and broadly lowered phytohormone concentrations, while significantly reshaping the bacterial community, with a higher relative abundance of Proteobacteria. Specific bacterial genera, including Proteus, Providencia and Morganella, were positively associated with key hormones, suggesting that the frass microbiome helps shape its hormonal profile and may underlie the biostimulant effects of black soldier fly frass in soil–plant systems.

Microbial diversity and community structure in fress and recirculated black soldier fly frass.

References

2026

Plant biostimulants in Hermetia illucens frass: insights into fresh and recirculated frass

Ivã Guidini Lopes, Thomas Klammsteiner, Ondřej Vrobel, Petr Tarkowski, Cecilia Lalander, and Jean Wan Hong Yong

Plant Growth Regulation, Jun 2026

Abstract doi Bib PDF

This is the first and extensive study investigating the bioactive composition of black soldier fly larvae (BSFL) frass through liquid chromatography tandem mass spectrometry (LC-MS/MS), with specific focus on phytohormones and their links to frass microbial composition. Two types of frass were evaluated: fresh frass (Fr-Cycle 1), obtained after one larval bioconversion cycle of food waste; and recirculated frass (Fr-Cycle 2), produced by reintroducing fresh frass into a subsequent bioconversion cycle. Frass recirculation did not affect overall nutrient composition but resulted in marked reductions in humic (80%) and fulvic (65%) acid concentrations, likely due to further decomposition of organic matter during recirculation. In parallel, recirculation significantly altered the bacterial community, decreasing the relative abundance of Actinobacteria while increasing Proteobacteria. Saliently, this is the first mass spectrometric evidence for the presence of cytokinins (both cZ and tZ, as well as their precursors) in BSFL frass, but several other phytohormones were identified in frass at nanomolar levels, including auxins (IAA, PAA, IAM, among others), abscisic acid, salicylates, indoleamines and an ethylene precursor. Interestingly, specific microbial genera were found to be positively correlated with phytohormones, including Proteus, Providencia and Morganella. The potential connections between microorganisms, phytohormones and physico-chemical characteristics of frass might help explain the results reported in the current literature exploring frass as a biofertilizer or soil amendment. The results presented herein open possibilities for approaching BSFL frass research from a new perspective, paving the way for future studies aiming at a more mechanistic understanding of its interactions with soil, plants and microorganisms.
@article{lopes_plant_2026, title = {Plant biostimulants in {Hermetia} illucens frass: insights into fresh and recirculated frass}, issn = {1573-5087}, shorttitle = {Plant biostimulants in {Hermetia} illucens frass}, url = {https://doi.org/10.1007/s10725-026-01470-3}, doi = {10.1007/s10725-026-01470-3}, language = {en}, urldate = {2026-06-06}, journal = {Plant Growth Regulation}, author = {Lopes, Ivã Guidini and Klammsteiner, Thomas and Vrobel, Ondřej and Tarkowski, Petr and Lalander, Cecilia and Yong, Jean Wan Hong}, month = jun, year = {2026}, keywords = {Auxin, Black soldier fly, Cytokinin, Microbiome, My publications, Phytohormone, Signalling}, dimensions = true, }