Photosynthesis Inhibiting E ects of Pesticides on Sweet Pepper Leaves

Although a large number of pesticides of di erent compositions are regularly used in agriculture, the impact of pesticides on the physiology of field crops is not well understood. Pesticides can produce negative e ects on crop physiology—especially on photosynthesis—leading to a potential decrease in both the growth and the yield of crops. To investigate these potential e ects in greenhouse sweet peppers, the e ect of 20 insecticides and 2 fungicides (each sprayed with a wetting agent) on the photosynthesis of sweet pepper leaves was analyzed. Among these pesticides, nine caused significant reductions in photosynthetic activity. The e ects were observed in distinctive ways—either as a transitory drop of the photosynthetic-rate values, which was observed at two hours after the treatment and was found to have recovered after 24 h, or as a sustained reduction of these values, which remained substantial over a number of days. The results of this study suggest that the production of a crop may substantially benefit when the frequent use of pesticides can be substituted with alternative pest control methods (e.g., biological control). Our results advocate further investigation of the potential impact of pesticides, either alone or in combination, on the photosynthesis of crop plants

Combined effects of soil silicon and host plant resistance on planthoppers, blast and bacterial blight in tropical rice

Soil silicon enhances rice defenses against a range of biotic stresses. However, the magnitude of these effects can depend on the nature of the rice variety. We conducted a series of greenhouse experiments to examine the effects of silicon on planthoppers (Nilaparvata lugens [BPH] and Sogatella furcifera [WBPH]), a leafhopper (Nephotettix virescens [GLH]), blast disease (Magnaporthe grisea) and bacterial blight (Xanthomonas oryzae) in susceptible and resistant rice. We added powdered silica gel (SiO2) to paddy soil at equivalent to 0.25, 1.0, and 4.0 t ha−1. Added silicon reduced BPH nymph settling, but the effect was negligible under high nitrogen. In a choice experiment, BPH egg-laying was lower than untreated controls under all silicon treatments regardless of nitrogen or variety, whereas, in a no-choice experiment, silicon reduced egg-laying on the susceptible but not the resistant (BPH32 gene) variety. Stronger effects in choice experiments suggest that silicon mainly enhanced antixenosis defenses. We found no effects of silicon on WBPH or GLH. Silicon reduced blast damage to susceptible and resistant (Piz, Piz-5 and Pi9 genes) rice. Silicon reduced damage from a virulent strain of bacterial blight but had little effect on a less virulent strain in susceptible and resistant (Xa4, Xa7 and Xa4 + Xa7 genes) varieties. When combined with resistance, silicon had an additive effect in reducing biomass losses to plants infested with bacterial blight (resistance up to 50%; silicon 20%). We discuss how silicon-containing soil amendments can be combined with host resistance to reduce biotic stresses in rice

Photosynthesis Inhibiting Effects of Pesticides on Sweet Pepper Leaves

Although a large number of pesticides of different compositions are regularly used in agriculture, the impact of pesticides on the physiology of field crops is not well understood. Pesticides can produce negative effects on crop physiology―especially on photosynthesis―leading to a potential decrease in both the growth and the yield of crops. To investigate these potential effects in greenhouse sweet peppers, the effect of 20 insecticides and 2 fungicides (each sprayed with a wetting agent) on the photosynthesis of sweet pepper leaves was analyzed. Among these pesticides, nine caused significant reductions in photosynthetic activity. The effects were observed in distinctive ways—either as a transitory drop of the photosynthetic-rate values, which was observed at two hours after the treatment and was found to have recovered after 24 h, or as a sustained reduction of these values, which remained substantial over a number of days. The results of this study suggest that the production of a crop may substantially benefit when the frequent use of pesticides can be substituted with alternative pest control methods (e.g., biological control). Our results advocate further investigation of the potential impact of pesticides, either alone or in combination, on the photosynthesis of crop plants

Direct and indirect effects of planning density, nitrogenous fertilizer and host plant resistance on rice herbivores and their natural enemies

In rice ecosystems, seeding densities can be adjusted to compensate for lower nitrogen levels that reduce GHG emissions, or to increase farm profitability. However, density-induced changes to plant anatomy could affect herbivore-rice interactions, and alter arthropod community dynamics. We conducted an experiment that varied transplanting density (low or high), nitrogenous fertilizer (0, 60 or 150 kg added ha−1) and rice variety (resistant or susceptible to phloem-feeding insects) over two rice-growing seasons. Yields per plot increased with added nitrogen, but were not affected by variety or transplanting density. Planthopper and leafhopper densities were lower on resistant rice and in high-density field plots. Nitrogen was associated with higher densities of planthoppers, but lower densities of leafhoppers per plot. High planting densities and high nitrogen also increased rodent damage. The structure of arthropod herbivore communities was largely determined by season and transplanting density. Furthermore, two abundant planthoppers (Sogatella furcifera (Horváth) and Nilaparvata lugens (Stål)) segregated to low and high-density plots, respectively. The structure of decomposer communities was determined by season and fertilizer regime; total decomposer abundance increased in high-nitrogen plots during the dry season. Predator community structure was determined by season and total prey abundance (including decomposers) with several spider species dominating in plots with high prey abundance during the wet season. Our results indicate how rice plasticity and arthropod biodiversity promote stability and resilience in rice ecosystems. We recommend that conservation biological control, which includes a reduction or elimination of insecticides, could be promoted to attain sustainable rice production systems.info:eu-repo/semantics/publishedVersio

Reconnecting Farmers with Nature through Agroecological Transitions: Interacting Niches and Experimentation and the Role of Agricultural Knowledge and Innovation Systems

Sustainability transitions in agriculture are explored through an analysis of niche initiatives within a common production system, relying on sustainable transitions, multi-level perspectives, and agroecological frameworks, and involving multi-actor, agricultural knowledge, and innovation systems (AKIS). The article focuses on how experimental niches and sustainable activities affect farmers’ relationships with nature, and the reconceptualisation of the production system in which they operate, particularly where this system is embedded in less sustainable conventional or dominant regimes and landscapes. The need for fundamental changes, in the way that humans interact with nature, is widely argued for in order to achieve sustainable development, and farmers occupy a central role through participation in complex networks of agri-food systems. They have also found themselves disconnected from nature through conventional agri-industrial production practices. Four niches (biological control, ecological restoration, soil health, and ecological pond management) within the greenhouse sector of Almeria (SE Spain) are explored in a case study. Our results indicate that a farmer’s interaction with nature is functional, but through agroecological practices, a deeper understanding of the ecosystems in which greenhouse landscapes are embedded may be gained. As they become more connected to nature and benefit from ecosystem services, they can transition to more sustainable agricultural systems

Bioacoustics Reveal Species-Rich Avian Communities Exposed to Organophosphate Insecticides in Macadamia Orchards

Organophosphates are the most widely used insecticide class in agriculture. The effects of organophosphates on insectivorous birds can potentially reduce the capacity of these birds to regulate insect pest populations as well as jeopardizing the survival of vulnerable bird species in matrix habitats. In this study, we investigated the diversity of birds inhabiting commercial macadamia orchards in Australia and assessed community-wide exposure of birds to an organophosphate insecticide (trichlorfon). We also studied the impact of trichlorfon on arthropods, and how this affected bird activity. We used a novel approach, combining bird acoustic surveys, and three different arthropod trapping devices. Birds and arthropods were surveyed immediately before and after a trichlorfon application, in sprayed and unsprayed orchards, at six different sites. Surveys showed that trichlorfon applications produced no changes in bird activity, either at the species or community level. Only one species (Lichmera indistincta) showed a significant increase in acoustic activity after treatment. These results indicate that several (62) bird species, some of which have been noted as undergoing regional decline, are exposed to trichlorfon applications. Additionally, trichlorfon applications also produced rapid, negative impacts on certain arthropod groups, particularly spiders. Because almost (80%) of the bird species recorded in the study include arthropods in their diets, then arthropod contaminated by trichlorfon are likely consumed by these orchard-dwelling birds. We recommend that pest management should incorporate strategies to reduce wildlife exposure to toxic chemicals to meet the joint goals of crop production and wildlife conservation in structurally complex agricultural habitats

Emerging Patterns in Cultural Ecosystem Services as Incentives and Obstacles for Raptor Conservation

The Millennium Ecosystem Assessment proposed four categories of ecosystem services as regulating, provisioning, supporting and cultural. Of these, cultural services have been the most difficult to quantify despite playing a key role in developing society’s supporting services to ecosystems. By reviewing a series of case studies related to the cultural services derived from raptors, we examine relations between tangible ecosystem services and ‘knowledge’ and ‘beliefs’ as part of supporting services from human societies to ecosystems. We identified types of raptor regulating and provisioning services and patterns in service--knowledge-beliefs that defined positive or negative outcomes for raptor conservation. We also demonstrate how possible interactions between physical, experiential, physical-symbolic and representative-symbolic cultural services and between different stakeholders can create incentives or obstacles for conservation. Predictable patterns in service-knowledge-beliefs provide a framework upon which socio-cultural and ethnobiological aspects of raptor conservation may be combined with ecological research to support conservation initiatives. Based on these patterns we present examples of how cultural services might be employed to better promote raptor conservation while respecting the beliefs and traditions of stakeholders

Restoration of Rice Ecosystem Services: ‘Ecological Engineering for Pest Management’ Incentives and Practices in the Mekong Delta Region of Vietnam

Ecological engineering is an agroecological approach to pest management that has been adopted by thousands of rice farmers in the Mekong Delta Region of Vietnam. Farmers adopted the intervention as part of a heuristic approach to developing the technology. This study assesses the knowledge, attitudes and practices related to ecological engineering among participating and non-participating farmers. Interviews with 315 farmers revealed a diversity of practices under the umbrella of ecological engineering, all of which were associated with the establishment of linear vegetation strips as habitat for natural enemies. As a restoring service from society to the rice ecosystem, ecological engineering incorporated significant positive-feedback loops, particularly regarding the production of supplementary foods (provisioning services) and the aesthetic value (cultural services) of planted rice bunds. Participating farmers reported fewer insecticide applications to their main rice crop; they applied insecticides at a later crop growth stage (protecting pest regulating services); and they reported higher rice yields. However, a high dependency on government support, the role of agrochemical extensionists in providing information, a tendency to apply pesticides to vegetation strips and little change in the appreciation of wildlife-related services all threaten the social sustainability of the intervention. We recommend greater attention to optimizing linear strips to not only support natural enemies but to also enhance supplementary farm incomes while reducing material and labor costs

Effects of Intraspecific Competition and Larval Size on Bioconversion of Apple Pomace Inoculated with Black Soldier Fly

Waste from apple juice and cider industries (pomace) compares poorly against spent grains and other relatively high-nutrient wastes as a substrate for bioconversion by the black soldier fly (BSF: Hermetia illucens). However, global pomace production exceeds 24 million tonnes annually and novel management approaches are required to reduce waste to landfill. We examined the effects of BSF inoculation densities (intraspecific competition) and larval size categories on cohort weight gains and apple pomace waste reduction. We found that, by increasing larval densities, cohort biomass and bioconversion rates (BRs) increased; however, at very high densities (overcrowding), BRs declined and cohorts lost weight. Furthermore, larger larval size classes accelerated substrate desiccation, possibly because of greater demands for water by older larvae. Larger larvae have slower relative growth rates and BRs compared to smaller size categories and require comparatively less dry weight substrate. Our results suggest that overcrowding on low-nutrient substrates reduces BRs and could exaggerate differences between BSF relative performances in comparative studies, particularly if intraspecific interference competition for space and exploitation competition for water diminish BSF weight returns at the end of the bioconversion cycle. We make a series of recommendations for the use of BSF in pomace waste reduction

Spent Coffee Grounds Applied as a Top-Dressing or Incorporated into the Soil Can Improve Plant Growth While Reducing Slug Herbivory

Between 8 and 15 million tons of spent coffee grounds (SCG) are produced as global waste each year. To reduce waste to landfill, SCG are proposed as a carbon and nutrient source for degraded soils. SCG contain caffeine and other toxins that inhibit plant growth. However, they also repel slugs and snails. We examined whether partial decomposition can neutralize SCG to promote plant growth while maintaining anti-herbivore properties. We aged SCG for Hermetia illucens) frass. The aged SCG and frass were applied, either incorporated into soil or as a 1 cm top-dressing, to pots with radish and tomato seedlings. SCG treatments were also examined for direct (repellent) and indirect (plant-mediated) effects on four slug species (Arion ater, Deroceras laeve, Derocerus reticulatum and Lehmannia marginata). SCG of ≤7 months inhibited plant growth and development and reduced herbivory when incorporated into soil, whereas 14-month-old SCG promoted growth but had no effect on herbivory. When applied as a top-dressing, SCG at 7 months promoted growth and reduced herbivory through repellent and host quality effects—including possible systemic effects. Our results indicate that the benefits of SCG for radish and tomato growth and to reduce slug herbivory can be achieved simultaneously by applying partially decomposed SCG (aged for up to 8 months) as a top-dressing