The predatory mites (Phytoseiidae) tested to date cannot effectively control the mite pest Aculops lycopersici (Acari: Eriophyidae) due to the unfavorable characteristics of tomato leaves and stems. However, recent studies show that the phytoseiid, Typhlodromus (Anthoseius) recki, can feed on this pest. Because T. (A.) recki is naturally present in high densities on Mentha suaveolens and Phlomis fruticosa, we performed preliminary studies using these species as banker plants in laboratory and greenhouse conditions. In laboratory conditions, we analyzed the effect of banker plants inoculated with T. (A.) recki and co-planted with tomato plants (infested or not with A. lycopersici) at two banker to tomato plants ratios. T. (A.) recki dispersed and established on tomato plants. Higher predator densities were observed on infested plants when M. suaveolens was used as a banker plant with a ratio of one banker plant to two tomato plants. In greenhouse conditions, predators were introduced on tomato plants (infested with A. lycopersici) via branches of banker plants at two densities. T. (A.) recki significantly reduced the length and intensity of stem russeting and A. lycopersici densities. The number of T. (A.) recki on tomato plants was the highest using branches of M. suaveolens at the higher densities released. These results underscore the efficacy of T. (A.) recki in controlling A. lycopersici and open new avenues for the use of M. suaveolens as a reservoir of this predator.

Given the huge challenges agriculture has to face, both in Northern and Southern countries, a radical change in farming practices towards agroecology is required. Most scientific literature on the design of new farming systems describes de novo approaches, which focus on disruption and novelty, without any concern for the way to move from the current system to the innovative one. In this study, we highlight, for the first time, the particular traits of what we will call the step-by-step design approach. In this aim, we disentangled 9 case studies of practice change in commercial or experimental farms through the lens of theoretical frameworks derived from three scientific fields: design sciences, farming system research, and change pathways analysis. From data collected in each case study, and collective interactions among the authors of this paper, we identified commonalities across cases, in the aim to produce guidelines for actors willing to engage, characterize or support such design processes in the future. We thus show that step-by-step design appears as (i) a situated design process fueled by action, (ii) structured by iterative loops diagnosis – exploration – implementation – assessment, fostered by learning, (iii) progressively shaping a desirable unknown, (iv) supported by specific tools, and (v) intertwining individual and collective dimensions. This approach is well adapted to manage the agroecological transition: by its temporality, by its capacity to overcome knowledge gaps through learning, by its contribution to farmers' empowerment, and by its capacity to tailor solutions to local specificities. By doing so, it allows the progressive implementation of profound systemic changes. Finally, this article provides benchmarks to encourage increased Research & Development investment in this type of approach, contributing to open innovation, to enhance the agroecological transition.

To meet the challenges of sustainability in agricultural system design, reducing the dependency on synthetic plant protection products has become a core issue. There are currently two major reasons for farmers' decision to reduce their use of synthetic products: public policies, and the extralegal requirements of food supply chains. To reduce or eliminate synthetic plant protection products, agroecological crop protection (ACP) relying on the development of agroecology science and practices is a promising holistic approach focused on crop health overall. ACP requires a consistent combination of various agronomic practices at different spatiotemporal and trophic levels. Vegetable crops are minor crops facing the major challenges of producing high-quality produce and of controlling sanitary pressure on yields. Thus, agroecological vegetable systems must not only be adapted to official regulations and environmental parameters but must also comply with the specifications of the targeted food value chains (FVC), which are variable: marketing standards regarding cosmetic issues are very strict in long value chains, whereas they are more flexible in local short chains. Whereas fresh vegetable production is strongly challenged by the reduction of synthetic plant protection products, there are few studies that show how to design, manage and assess agroecological crop protection strategies for such systems, considering the main specifications and criteria of the FVC as a whole. This article reports on the challenges of complying with both FVC specifications and agroecology principles in protected vegetable crop protection. This study relies on four cropping systems implemented in an experimental station for 4.5 years, each of which had a specific strategy of crop protection management and was devoted to a particular FVC. The four FVCs are “local direct sale in low-pesticide farming”, “local direct sale in organic farming”, “super- and hypermarket value chain in low-pesticide farming” and “super- and hypermarkets value chain in organic farming”. Results consist in the description of combination of agronomic practices used, as well as the corresponding decision-making processes. They then present the performance of the four systems tested, showing that agroecological crop protection strategies are successful in reducing or eliminating synthetic plant protection products. We then discuss failure and success factors highlighted by this multi-year experiment. It illustrates that agroecological crop protection and compliance with the FVC's expectations can be compatible but involve specific trade-offs, depending on the targeted food value chain. We finally stress key areas to investigate further in order to achieve still challenging objectives in vegetable systems.

AbstractIn tropical ecosystems, ants represent a substantial portion of the animal biomass and contribute to various ecosystem services, including pest regulation and pollination. Dominant ant species are known to determine the structure of ant communities by interfering in the foraging of other ant species. Using bait and pitfall trapping experiments, we performed a pattern analysis at a fine spatial scale of an ant community in a very simplified and homogeneous agroecosystem, that is, a single‐crop banana field in Martinique (French West Indies). We found that the community structure was driven by three dominant species (Solenopsis geminata, Nylanderia guatemalensis, and Monomorium ebeninum) and two subdominant species (Pheidole fallax and Brachymyrmex patagonicus). Our results showed that dominant and subdominant species generally maintained numerical dominance at baits across time, although S. geminata, M. ebeninum, and B. patagonicus displayed better abilities to maintain dominance than P. fallax and N. guatemalensis. Almost all interspecific correlations between species abundances, except those between B. patagonicus and N. guatemalensis, were symmetrically negative, suggesting that interference competition prevails in this ground‐dwelling ant community. However, we observed variations in the diurnal and nocturnal foraging activity and in the daily occurrence at baits, which may mitigate the effect of interference competition through the induction of spatial and temporal niche partitioning. This may explain the coexistence of dominant, subdominant, and subordinate species in this very simplified agroecosystem, limited in habitat structure and diversity.

Design, experimentation and assessment of four protected vegetable cropping systems adapted to different food systems. 5. International Symposium for Farming Systems Design (AGRO2015)

In different agroecosystems, intercropping has proved to be a promising way to reduce pesticide use, as it can reduce risks of pests or diseases damages (i) by limiting their dispersal (physical or chemical processes) and (ii) by diversifying resources for natural enemies. However, up to now, intercropping in protected market gardening is poorly referenced. Biological processes operating in specific crop combinations are only partially understood and guidelines to design and manage these complex agro ecosystems are scarce. However, few market gardeners already develop intercropping under shelter on diversified farming systems. In order to design innovative cropping systems, we developed a participatory research program involving producers, extension agents and researchers. This research combined: (i) the organization of design workshops gathering these stakeholders. During these workshops, we collectively explored hitherto unseen ways, to design prototypes of innovative intercropping systems aiming at reducing pesticide reduction; (ii) the tracking of on-farm systems based on intercropping. We looked out for the rare intercropping systems developed by farmers to analyze their agronomical logics (practices, objectives inherent to their development) and their performances; (iii) the on-station experiment of innovative intercropping systems. System experiments allowed us to analyze biological processes operating in intercropping and to assess the performances of such systems. Combining these different resources allowed us to explore the complexity and diversity of intercropping systems as well as the diversity of motivations driving farmers to develop them, in order to discuss their benefits and drawbacks. This communication aims to present results of this method which led (i) to design prototypes which were tested and assessed on station, and (ii) to identify guidelines to design, assess and manage intercropping systems suited to contrasted farming systems.

Understanding the mechanisms underlying the movements and spread of a species over time and space is a major concern of ecology. Here, we assessed the effects of an individual's sex and the density and sex ratio of conspecifics in the local and neighboring environment on the movement probability of the banana weevil, Cosmopolites sordidus. In a two patches experiment, we used radiofrequency identification tags to study the C.sordidus movement response to patch conditions. We showed that local and neighboring densities of conspecifics affect the movement rates of individuals but that the density-dependent effect can be either positive or negative depending on the relative densities of conspecifics in local and neighboring patches. We demonstrated that sex ratio also influences the movement of C.sordidus, that is, the weevil exhibits nonfixed sex-biased movement strategies. Sex-biased movement may be the consequence of intrasexual competition for resources (i.e., oviposition sites) in females and for mates in males. We also detected a high individual variability in the propensity to move. Finally, we discuss the role of demographic stochasticity, sex-biased movement, and individual heterogeneity in movement on the colonization process.

Ralstonia solanacearum is responsible for bacterial wilt affecting many crops worldwide. The emergent population of R.solanacearum (phylotype IIB/4NPB) wilts previously resistant varieties and has rapidly spread throughout Martinique. No conventional method is known to control it. In this study, previous crops used as sanitizing crops were investigated as an environmentally safe alternative method of control. The ability of the emergent population of R.solanacearum to persist in planta and in the rhizosphere of Brassicaceae, Asteraceae and Fabaceae grown as previous crops was evaluated in controlled conditions, and the incidence of bacterial wilt was assessed in the following tomato crop. Results showed that all species carried R.solanacearum latently. Among Brassicaceae and Asteraceae, the highest density of R.solanacearum was found in planta and in the rhizosphere of Tagetes erecta. The density of the R.solanacearum population in the rhizosphere of Raphanus sativus cv. Karacter was significantly higher than that in Raphanus sativus cv. Melody. In Fabaceae, the density of R.solanacearum population in planta was statistically similar in all species. The density of the R.solanacearum population in the rhizosphere of Crotalaria juncea was significantly higher than that in Crotalaria spectabilis. This study showed for the first time that Crotalaria spectabilis and Raphanus sativus cv. Melody grown as previous crops improve the performance of the following tomato with similar effects on R.solanacearum populations in the soil as bare soil. The incidence of the disease in tomato decreased by 86% and 60%, after R.sativus cv. Melody and C.spectabilis, respectively, and the proportion of infected plants also decreased. These results suggest that C.spectabilis and R.sativus cv. Melody can be used as previous crops to help bacterial wilt control in ecological management strategies without drastic suppression of R.solanacearum population in stem tissues and in the rhizosphere.

To control bacterial wilt (Ralstonia solanacearum, phylotype IIB/4NPB), the antimicrobial effect of Allium fistulosum aqueous extract was assessed as a preplant soil treatment. Three concentrations of extract (100, 50, and 25%, 1:1 [wt/vol]) were evaluated by in vitro inhibition assay and in vivo experiments in a growth chamber. In vitro, A. fistulosum (100 and 50%) suppressed growth of R. solanacearum. Preplant treatment of the soil with A. fistulosum extract significantly reduced the R. solanacearum populations. No pathogen was detected in the soil after treatment with 100% concentrated extract from the third day after application until the end of the experiment. A. fistulosum also significantly reduced the incidence of tomato bacterial wilt. In the untreated control, the disease affected 61% of the plants whereas, with 100 and 50% extracts, only 6 and 14% of the plants, respectively, were affected. These results suggest that A. fistulosum extracts could be used in biocontrol-based management strategies for bacterial wilt of tomato.