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Frass, a byproduct of insect rearing, has become popular for its potential use in sustainable agriculture. The rapid growth of insect production results in an increased frass output. This study examined the effects of frass as soil amendment on plant growth and resistance to insect herbivory. In greenhouse experiments, Brassica rapa L. (Brassicaceae), was grown in unamended soil (NoFrass; control) or soil amended with frass (2 g kg−1) from larvae of black soldier fly (BSFF), Hermetia illucens L. (Diptera: Stratiomyidae), or yellow mealworm (MWF), Tenebrio molitor L. (Coleoptera: Tenebrionidae). Frass was applied as raw, incubated, or composted frass before seed germination. Plant growth and performance were measured of larvae of root‐feeding Delia radicum L. (Diptera: Anthomyiidae) and shoot‐feeding Plutella xylostella L. (Lepidoptera: Plutellidae). Initially, raw BSFF and MWF reduced the growth of B. rapa and resulted in a smaller leaf area than NoFrass. However, over time, a notable trend emerged. Whereas the difference in leaf area between MWF and NoFrass disappeared, BSFF consistently resulted in a smaller leaf area than MWF and NoFrass. Raw BSFF reduced D. radicum larval survival and pupal biomass and larval survival of P. xylostella. In contrast, raw MWF increased larval survival and biomass of D. radicum and the survival of P. xylostella larvae. Interestingly, incubation of frass in the soil for 16 days before seed germination removed plant growth inhibition and increased plant leaf area, especially for MWF compared to NoFrass. In addition, composting MWF increased leaf growth. Therefore, frass may be used as a sustainable and natural alternative to conventional organic fertilisers, promoting plant growth and enhancing resistance to herbivory. Our results indicate that soil amendment with raw BSFF may negatively impact herbivore performance, whereas raw MWF may enhance herbivore performance. [ABSTRACT FROM AUTHOR]

While the response of Arabidopsis thaliana to drought, herbivory or fungal infection has been well‐examined, the consequences of exposure to a series of such (a)biotic stresses are not well studied. This work reports on the genetic mechanisms underlying the Arabidopsis response to single osmotic stress, and to combinatorial stress, either fungal infection using Botrytis cinerea or herbivory using Pieris rapae caterpillars followed by an osmotic stress treatment. Several small‐effect genetic loci associated with rosette dry weight (DW), rosette water content (WC), and the projected rosette leaf area in response to combinatorial stress were mapped using univariate and multi‐environment genome‐wide association approaches. A single‐nucleotide polymorphism (SNP) associated with DROUGHT‐INDUCED 19 (DI19) was identified by both approaches, supporting its potential involvement in the response to combinatorial stress. Several SNPs were found to be in linkage disequilibrium with known stress‐responsive genes such as PEROXIDASE 34 (PRX34), BASIC LEUCINE ZIPPER 25 (bZIP25), RESISTANCE METHYLATED GENE 1 (RMG1) and WHITE RUST RESISTANCE 4 (WRR4). An antagonistic effect between biotic and osmotic stress was found for prx34 and arf4 mutants, which suggests PRX34 and ARF4 play an important role in the response to the combinatorial stress. [ABSTRACT FROM AUTHOR]

Plants can detect neighbouring plants through a reduction in the ratio between red and far‐red light (R:FR). This provides a signal of plant–plant competition and induces rapid plant growth while inhibiting defence against biotic stress, two interlinked responses designated as the shade avoidance syndrome (SAS). Consequently, the SAS can influence plant–herbivore interactions that could cascade to higher trophic levels. However, little is known about how the expression of the SAS can influence tritrophic interactions. We investigated whether changes in R:FR affect the emission of herbivore‐induced plant volatiles (HIPVs), and whether these changes influence the attraction of the zoophytophagous predator Macrolophus pygmaeus. We also studied how the expression of the SAS and subsequent inhibition of plant defences affects the reproduction of M. pygmaeus in both the presence and absence of the greenhouse whitefly (WF) (Trialeurodes vaporariorum) as arthropod prey. The results show that changes in R:FR have little effect on HIPV emissions and predator attraction. However, a reduction in R:FR leads to increased reproduction of both the predator and the WFs. We discuss that shade avoidance responses can increase the population development of M. pygmaeus through a combination of reduced plant defences and increased herbivore densities. Summary statement: Changes in red and far‐red light (FR) have little influence on the emission of volatiles by tomatoes and also do not influence the attraction of the predatory bug Macrolophus pygmaeus. However, FR light does increase M. pygmaeus reproduction on tomatoes, both in the absence and presence of whiteflies (WFs) as arthropod prey. This is related to reduced plant defences in FR light and increased WF densities. [ABSTRACT FROM AUTHOR]