Cabbage root fly （Delia radicum L.） control represents a major challenge in brassica production, therefore different management strategies for its control were tested in conventionally managed open field cauliflower...Cabbage root fly （Delia radicum L.） control represents a major challenge in brassica production, therefore different management strategies for its control were tested in conventionally managed open field cauliflower production. Strategies included treatments with low-risk methods such as nitrogen lime, the insecticide spinosad and the Beauveria bassiana ATCC 74040-based biopesticide Naturalis. Their effects were compared with treatments based on nonformulated fungal species Metarhizium brunneum, B. bassiana, Clonostachys solani, Trichoderma atroviride, T. koningiopsis, and T. gamsii and commercial insecticides λ-cyhalothrin and thiamethoxam. Spinosad and thiamethoxam were pipetted to individual plants before transplanting; λ-cyhalothrin was sprayed after transplanting; nitrogen lime was applied at first hoeing. Nonformulated fimgi were delivered onto cauliflower plantlets＇ roots as a single pretransplantation inoculation. The cabbage root fly population dynamics exhibited a strong spatiotemporal variation. The lowest number of cabbage root fly pupae recovered from cauliflower roots in the field experiments was recorded in plants treated with spinosad （significant reduction）, followed by Naturalis and one of the tested M. brunneurn strains （nonsignificant reduction）. Significantly more pupae were counted in the nitrogen lime treatment. The field experiments showed that a single drench of cauliflower plantlets with spinosad offered consistent and enduring cabbage root fly control. Naturalis and nonformulated fungal isolates did not decrease cabbage root fly pressure significantly, apparently due to lack of statistical power. The implications of the substantial intra- and inter-annual pest pressure variation and the benefits of using single plant treatments are discussed, and recommendations for improvement of rhizosphere-competence utilizing biological control strategies provided.展开更多
Interactions between plants and phytophagous insects play an important part in shaping the biochemical composition of plants. Reciprocally plant metabolites can influ- ence major life history traits in these insects a...Interactions between plants and phytophagous insects play an important part in shaping the biochemical composition of plants. Reciprocally plant metabolites can influ- ence major life history traits in these insects and largely contribute to their fitness. Plant rhizospheric microorganisms are an important biotic factor modulating plant metabolites and adaptation to stress. While plant-insects or plant-microorganisms interactions and their consequences on the plant metabolite signature are well-documented, the impact of soil microbial communities on plant defenses against phytophagous insects remains poorly known. In this study, we used oilseed rape （Brassica napus） and the cabbage root fly （Delia radicum） as biological models to tackle this question. Even though D. radicum is a belowground herbivore as a larva, its adult life history traits depend on aboveground signals. We therefore tested whether soil microbial diversity influenced emergence rate and fitness but also fly oviposition behavior, and tried to link possible effects to modifications in leaf and root metabolites. Through a removal-recolonization experiment, 3 soil microbial modalities （＂high,＂ ＂medium,＂ ＂low＂） were established and assessed through amplicon sequencing of 16S and 18S ribosomal RNA genes. The ＂medium＂ modality in the rhizosphere significantly improved insect development traits. Plant-microorganism interactions were marginally associated to modulations of root metabolites profiles, which could partly explain these results. We highlighted the potential role of plant-microbial interaction in plant defenses against Delia radicum. Rhizospheric microbial communities must be taken into account when analyzing plant defenses against herbivores, being either below or aboveground.展开更多
文摘Cabbage root fly （Delia radicum L.） control represents a major challenge in brassica production, therefore different management strategies for its control were tested in conventionally managed open field cauliflower production. Strategies included treatments with low-risk methods such as nitrogen lime, the insecticide spinosad and the Beauveria bassiana ATCC 74040-based biopesticide Naturalis. Their effects were compared with treatments based on nonformulated fungal species Metarhizium brunneum, B. bassiana, Clonostachys solani, Trichoderma atroviride, T. koningiopsis, and T. gamsii and commercial insecticides λ-cyhalothrin and thiamethoxam. Spinosad and thiamethoxam were pipetted to individual plants before transplanting; λ-cyhalothrin was sprayed after transplanting; nitrogen lime was applied at first hoeing. Nonformulated fimgi were delivered onto cauliflower plantlets＇ roots as a single pretransplantation inoculation. The cabbage root fly population dynamics exhibited a strong spatiotemporal variation. The lowest number of cabbage root fly pupae recovered from cauliflower roots in the field experiments was recorded in plants treated with spinosad （significant reduction）, followed by Naturalis and one of the tested M. brunneurn strains （nonsignificant reduction）. Significantly more pupae were counted in the nitrogen lime treatment. The field experiments showed that a single drench of cauliflower plantlets with spinosad offered consistent and enduring cabbage root fly control. Naturalis and nonformulated fungal isolates did not decrease cabbage root fly pressure significantly, apparently due to lack of statistical power. The implications of the substantial intra- and inter-annual pest pressure variation and the benefits of using single plant treatments are discussed, and recommendations for improvement of rhizosphere-competence utilizing biological control strategies provided.
文摘Interactions between plants and phytophagous insects play an important part in shaping the biochemical composition of plants. Reciprocally plant metabolites can influ- ence major life history traits in these insects and largely contribute to their fitness. Plant rhizospheric microorganisms are an important biotic factor modulating plant metabolites and adaptation to stress. While plant-insects or plant-microorganisms interactions and their consequences on the plant metabolite signature are well-documented, the impact of soil microbial communities on plant defenses against phytophagous insects remains poorly known. In this study, we used oilseed rape （Brassica napus） and the cabbage root fly （Delia radicum） as biological models to tackle this question. Even though D. radicum is a belowground herbivore as a larva, its adult life history traits depend on aboveground signals. We therefore tested whether soil microbial diversity influenced emergence rate and fitness but also fly oviposition behavior, and tried to link possible effects to modifications in leaf and root metabolites. Through a removal-recolonization experiment, 3 soil microbial modalities （＂high,＂ ＂medium,＂ ＂low＂） were established and assessed through amplicon sequencing of 16S and 18S ribosomal RNA genes. The ＂medium＂ modality in the rhizosphere significantly improved insect development traits. Plant-microorganism interactions were marginally associated to modulations of root metabolites profiles, which could partly explain these results. We highlighted the potential role of plant-microbial interaction in plant defenses against Delia radicum. Rhizospheric microbial communities must be taken into account when analyzing plant defenses against herbivores, being either below or aboveground.
