Benjamin Joubard’s research while affiliated with École Nationale Supérieure des Sciences Agronomiques de Bordeaux-Aquitaine and other places

In most viticulture countries, the grape phylloxera (GP) Daktulosphaira vitifoliae (Fitch) (Hemiptera: Phylloxeridae) is controlled by planting grafted plants on rootstocks resistant to this pest. In the search for alternative protective methods, the effectiveness of Metarhizium robertsii in protecting non-grafted Vitis vinifera grapevines against radicicole GP was assessed in vitro. In the first approach, GP eggs from a single clonal lineage were infected with M. robert- sii strain EF3.5(2) obtained from a French vineyard. In bioassays, three application methods (egg spraying, root spraying, and both) were assessed using fresh woody root sections of V. vinifera cv. Cabernet Sauvignon. M. robertsii pathogenic effect translated to a significant reduction of 90.0 % by the egg spraying, 70.0 % by the root spraying, and 86.1 % by spray- ing both in the survival probability of GP larvae and adults compared to controls, and 92.0 %, 89.0 % and 93.0 % in the reduction of successful development to the adult stage after 28 days post-treatment, respectively. In the second approach, the impact of M. robertsii’s association with non-grafted V. vinifera roots on radicicole GP establishment and symptom induction was assessed in a pot experiment. After 76 days post-GP inoculation, a remarkable 91 % reduction in damage was observed in plants co-inoculated with M. robertsii and GP, compared to those infected solely with GP. Furthermore, 100 % of M. robertsii-inoculated plants and 92.0 % of GP-M. robertsii co-inoculated plants were colonized by the fungus at the rhizosphere level. Notably, grapevine growth remained unaffected during the trial by neither M. robertsii inocula- tion nor GP infestation. In conclusion, these findings highlight the potential of M. robertsii for durable association and GP biocontrol in non-grafted grapevines. Future investigations are warranted under field conditions to validate and optimize the larger-scale practical application of this biocontrol strategy.

Decline in species richness as well as changes in community evenness or functional diversity have been hypothesised to jointly affect ecosystem functioning. However, disentangling the relative effects of these changes in community structure is hard as these different aspects often covary with species richness in real‐world ecosystems. In this study, we investigated the individual and interactive effects of functional diversity and community evenness of predators on the level of control of herbivorous prey. Using a highly replicated mesocosm experiment, we crossed three levels of functional diversity of arthropod predators with two levels of community evenness while controlling for the effect of species richness. Using this experimental setting, we hypothesised that the effect size of functional diversity of predators depends on community evenness. We expected a positive effect of functional diversity of predators on top‐down control at high level of community evenness while we thought that species identity and their associated traits should drive most of the effect on top‐down control at low level of community evenness. Our results did not provide any evidence for an interaction between functional diversity and community evenness nor any beneficial effect of increased functional diversity overall on predation rates of herbivorous prey. In addition, our results revealed that species and functional identity drives most of the effects of predator community composition on top‐down control of their prey in our study system. Assemblages composed of active hunters with low handling time and no starvation ability tended to have the highest impacts on prey biomass. By indicating that top‐down control of herbivorous prey by arthropod predators is mainly driven by species and functional identity and not by functional diversity, our study provides insights into the consequences of ongoing species loss on ecosystem functioning. Future research should now explore the predictability of trophic interactions based on functional traits of predator and herbivorous prey to anticipate the consequences of changes in species composition on ecosystem functioning. Read the free Plain Language Summary for this article on the Journal blog.

Organic farming is a promising but still debated option to ensure sustainable agriculture. However, whether organic farming fosters synergies or mitigates tradeoffs between biodiversity, ecosystem services and crop production has rarely been quantified. Here, we investigate relationships between multitrophic diversity (14 taxa above and belowground), yield, natural pest control and soil quality (14 proxies of ecosystem services) in organic and conventional vineyards along a landscape gradient. Organic farming enhanced biodiversity and pest control, but decreased wine production. Compared to conventional systems, multitrophic diversity was 15 % higher, and pest control services were 9 % higher in organic systems, while wine production was 11 % lower. Regardless of management type, we found a strong tradeoff between wine production and pest control, but not between wine production and biodiversity. The landscape context was not a strong moderator of organic farming effects across taxa groups and ecosystem services, but affected specific taxa and ecosystem services, especially natural pest control. Our study reveals that wine production and biodiversity conservation do not necessarily exclude each other, which implies the existence of a safe operating space where biodiversity and wine production can be combined. We conclude that organic farming can contribute to improve the sustainability of viticulture, but needs to be complemented by management options at the local and landscape scales in order to fully balance biodiversity conservation with the simultaneous provision of multiple ecosystem services.

Understanding the response of biodiversity to organic farming is crucial to design more sustainable agriculture. While it is known that organic farming benefits biodiversity on average, large variability in the effects of this farming system exists. Moreover, it is not clear how different practices modulate the performance of organic farming for biodiversity conservation. In this study, we investigated how the abundance and taxonomic richness of multiple species groups responds to certified organic farming and conventional farming in vineyards. Our analyses revealed that farming practices at the field scale are more important drivers of community abundance than landscape context. Organic farming enhanced the abundances of springtails (+ 31.6%) and spiders (+ 84%), had detrimental effects on pollinator abundance (− 11.6%) and soil microbial biomass (− 9.1%), and did not affect the abundance of ground beetles, mites or microarthropods. Farming practices like tillage regime, insecticide use and soil copper content drove most of the detected effects of farming system on biodiversity. Our study revealed varying effects of organic farming on biodiversity and clearly indicates the need to consider farming practices to understand the effects of farming systems on farmland biodiversity.

An amendment to this paper has been published and can be accessed via the original article.

Background: Although native to North America, the invasion of the aphid-like grape phylloxera Daktulosphaira vitifoliae across the globe altered the course of grape cultivation. For the past 150 years, viticulture relied on grafting-resistant North American Vitis species as rootstocks, thereby limiting genetic stocks tolerant to other stressors such as pathogens and climate change. Limited understanding of the insect genetics resulted in successive outbreaks across the globe when rootstocks failed. Here we report the 294-Mb genome of D. vitifoliae as a basic tool to understand host plant manipulation, nutritional endosymbiosis, and enhance global viticulture. Results: Using a combination of genome, RNA, and population resequencing, we found grape phylloxera showed high duplication rates since its common ancestor with aphids, but similarity in most metabolic genes, despite lacking obligate nutritional symbioses and feeding from parenchyma. Similarly, no enrichment occurred in development genes in relation to viviparity. However, phylloxera evolved > 2700 unique genes that resemble putative effectors and are active during feeding. Population sequencing revealed the global invasion began from the upper Mississippi River in North America, spread to Europe and from there to the rest of the world. Conclusions: The grape phylloxera genome reveals genetic architecture relative to the evolution of nutritional endosymbiosis, viviparity, and herbivory. The extraordinary expansion in effector genes also suggests novel adaptations to plant feeding and how insects induce complex plant phenotypes, for instance galls. Finally, our understanding of the origin of this invasive species and its genome provide genetics resources to alleviate rootstock bottlenecks restricting the advancement of viticulture.

Landscape complexity can benefit natural enemy communities and the biological pest control services they provide in agricultural landscapes. Harvestmen are generalist predators consuming a large range of prey in terrestrial ecosystems including agroecosystems. However, their ecology and their role in controlling pest populations in such ecosystems remain poorly studied. In this study, we examined predator-prey interactions between the European harvestmen (Phalangium opilio L.) and several potential prey species found in a vineyard agroecosystem. We sampled 20 populations of harvestmen in vineyards selected along a gradient of proportion of semi-natural habitats and used gut-content molecular analyses to quantify interaction strength between harvestmen and the grape berry moth, the main insect pest of grape, and two alternative prey species, springtails and the grape phylloxera. We found a high proportion of harvestmen positive to each type of prey with, on average, half of the individuals collected that had consumed grape berry moths. Increasing the proportion of semi-natural habitats in the landscape enhanced the proportion of harvestmen preying upon grape berry moths. Despite a significant number of harvestmen preying on springtails and grape phylloxera, the strength of the feeding interaction between harvestmen and these alternative prey species never significantly explained predation rates of the grape berry moth. Our results indicate that conserving semi-natural habitats increases biological pest control services delivered by harvestmen in vineyard landscapes and highlight the potentially important role of harvestmen in those agricultural systems.