Rearing insects is expected to dramatically increase during the next few years, and this will be associated with generating high quantities of frass (insect excreta). It is necessary to find solutions allowing the efficient valorization of these by-products before a major upscaling of the industry takes place. therefore, this study aims at investigating the fertilizer potential of frass. A pot experiment was established and soil was amended either with mealworm (Tenebrio molitor L.) frass (10 Mg ha −1 ), with mineral fertilizer (NPK) at equivalent nutrient level to frass or with a mixture of 50% NPK and 50% frass. Changes of soil properties and growth and nutrient uptake by barley (Hordeum vulgare L.) were then analyzed. Due to its rapid mineralization and the presence of nutrient in a readily-available form, we found that frass is as efficient as mineral NPK fertilizer to improve biomass and N, P and K uptake by barley. Compared to mineral fertilizer, water soluble P concentration is five times lower in the presence of frass, which prevents p from loss and sorption onto soil constituents. More importantly, BioLoG ecoplate reveals that addition of frass stimulates soil microbial activity, especially when it is mixed with mineral fertilizer, suggesting a synergistic effect between both amendments. Taken together, our results indicate that frass has a great potential to be used as a partial or a complete substitute for mineral npK fertilizer. this is especially relevant in the context of a reduced availability of mineral fertilizers while being consistent with circular economy's principles.

1 The disruption of host-finding cues has been proposed as a key mechanism underlying the lower damage caused by phytophagous insects in mixed forests. We tested this hypothesis by investigating the distribution of pine processionary moth Thaumetopoea pityocampa (Denis & Schiffer-Müller) (Lepidoptera) infestation at the edges of pure stands of Pinus pinaster (Aïton) at some distance from nonhost trees (Experiment 1) or bordered in part by a broadleaved hedgerow (Experiment 2). 2 An 'edge effect' was demonstrated, with trees at the edge of the stand being more heavily infested than those at the interior of the stand. 3 The presence of a nonhost broadleaved hedgerow in front of the edge of the pine stand resulted in lower T. pityocampa infestation. There were significantly fewer T. pityocampa nests behind the hedgerow than on the exposed part of the edge. The presence of the hedgerow did not dilute or repel T. pityocampa infestation further into the pine stand, although it decreased the infestation of T. pityocampa throughout the pine stand. The decrease in T. pityocampa infestation behind the hedgerow was greater when the broadleaved hedgerow was taller than the pine trees. 4 These results highlight the benefits of using nonhost tree species on the edge of monospecific forest stands to reduce insect damage. This approach could be promoted as an innovative forest pest management method.

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