Pest Suppression Research Articles

Spatiotemporal isolation of oilseed rape fields reduces insect pest pressure and crop damage

Abstract Pest management is essential to maintain agricultural production, but recent shifts in policies and the development of insecticide resistance have restricted the availability of insecticides for pest suppression. Identifying the landscape‐level resource requirements of pests to complete their life cycles might unveil new sustainable solutions to regulate their populations and prevent crop damage. We assessed the effects of landscape composition and configuration at different spatial scales on flea beetle densities and crop damage in 56 spring oilseed rape fields sampled over 5 years in Sweden. We considered the cover of non‐crop habitats as an aspect of landscape composition and the distances to the host crop and an alternative host crop in the previous year, edge density and crop diversity as aspects of landscape configuration. The distance from spring oilseed rape in the previous year reduced flea beetle densities and crop damage across most species and spatial scales. Edge density reduced the densities of two flea beetle species, predominantly at the 500 m radius landscape scale. The cover of forests and permanent pastures as well as crop diversity in the previous year increased the densities of different species at several, mostly larger (1000–2000 m) spatial scales. Increasing permanent pasture cover at the 500 m scale also increased crop damage. Synthesis and applications: We find that there is no one fits all approach in designing landscapes for flea beetle regulation as habitat use and scales of effect are species‐specific for these pests. However, increasing the spatiotemporal isolation of host crop fields is a promising and potentially more general means of disrupting pest populations and reducing crop damage. Considering the ecological traits of the pest species is a possible next step to optimise landscape‐based pest management.

Recent advances in agroecological research for increasing scope of areawide pest management of arthropods in cropping systems.

We propose that a growing research base considering pest management as an ecosystem service can be leveraged to expand areawide pest management (AWPM) to an agroecological-oriented framework when addressing pest arthropods in cropping systems. This AWPM framework centers on the innate capacity of the agroecosystem to suppress pests and is supported with strategic insertion of AWPM tactics. Recent studies on agroecological pest management are valuable to identify AWPM candidates. The estimation and predictability of AWPM outcomes may be improved by measuring effects of interactions of pest and pest suppression agents, and mediating factors such as landscape and weather. This knowledge helps formulate selection and strategic insertion of AWPM tactics into the system to support innate pest suppression. Advances in biotechnology and agricultural engineering have increased effectiveness of AWPM tactics, further improving positive AWPM outcomes. Furthermore, multifunctional agricultural, environmental, and economic benefits may be seen when adopting this framework.

Pest suppression potential varies across 10 bioenergy cropping systems

AbstractTop‐down suppression of herbivores is a fundamental ecological process and a critical service in agricultural landscapes. Adoption of bioenergy cropping systems is likely to become an increasingly important driver causing loss or gain of this service in coming decades. We measured natural pest suppression potential in ten model bioenergy crops in a long‐term experimental array by deploying plasticine sentinel caterpillar mimics, which record imprints from predator attacks. Cropping systems included three intensive annual row crop systems and a range of simple perennial monocultures and more complex polycultures. We compared attack rates across the ten cropping systems and assessed differences over time within a growing season and between the ground level and canopy. We found strong differences in attack rates across cropping systems, usually with more attacks in perennial crops than annuals. However, outcomes varied in space and time, both within and among cropping systems. Birds and small mammals were responsible for most, and sometimes all, attacks in annual crops and were most important early in the season. Chewing arthropod attacks increased over the course of the growing season and were responsible for most attack events in perennial systems. In late summer there were almost no attacks in annual crop canopies, while attack rates in perennial canopies at the same time were quite high and were carried out almost entirely by chewing arthropods. Our results underscore the lack of trophic complexity in annual bioenergy cropping systems relative to perennials. They also illustrate the dramatic changes in predator activity and predation intensity that occur both seasonally and between the ground and plant canopy. Policies and practices that increase the footprint of annual crops for bioenergy are likely to cause a deficit in pest suppression services at local and landscape scales.

Photoselective particle films influence physiology and growth of citrus

Particle films impact pest management and crop physiology by redistributing light within the canopy. Although most commercial particle film products have nonselective reflectance, recent studies found positive effects of a red-dyed particle film on pest suppression and growth in citrus. To better understand the impacts of photoselective particle films on tree physiology and growth, we implemented a series of trials in citrus. Photoselective particle films of white (undyed), red, blue, purple, and green color were developed using photostable dyes. The experiment was repeated three times. In Trials 1 and 2 treatment rates were the same quantity of kaolin per treatment. However, because different photoselective films provided differences in shading, in Trial 3 the kaolin rates were adjusted to result in the same incident radiation to the leaves. We measured gas exchange and leaf temperatures midmorning and midday on multiple dates. All particle film treatments reduced leaf temperature (∼ 4–8 °C). Depending on environmental conditions, some particle films increased net CO2 assimilation or stomatal conductance especially white and red. Trees growing under red and white films resulted in higher total dry weights compared to the other colored films, and red films had the highest mean in all three trials. Photoselective particle films impacted both quantity and quality of incident radiation. The red-dyed kaolin film resulted in the best growth and physiological responses in citrus. These products represent an easily deployable technology to manipulate the light environment of crops in the field.

Crop diversity and edge density benefit pest suppression through bottom-up and top-down processes, respectively

Agricultural intensification has resulted in the homogenization of agricultural landscapes, leading to the loss of crop and habitat diversity, and a higher rate of chemical inputs in the landscape, negatively impacting natural enemy communities and their ability to provide pest control services. Landscape heterogeneity is thought to benefit predator populations (increasing landscape complementation) and lower pest colonization (decreasing resource concentration); however, few studies have determined the relative importance of these two processes in pest suppression. Here, we tease apart direct and indirect impacts of landscape heterogeneity on experimental populations of soybean aphid excluded from and open to predation, in 23 soybean fields in Manitoba, in 2017 and 2018. Field plant counts and sweep net samples were conducted to determine aphid and predator abundances, respectively, and Malaise traps were used to quantify predator movement into soybean. Landscape effects differed between a soybean aphid outbreak year (2017) versus a non-outbreak year (2018). We found that crop diversity at a 1.5 km radius had negative impacts on aphid colonization during the outbreak year, resulting in greater aphid suppression but no impacts on predator movement. Edge density at a 1.5 km radius increased aphid suppression during the low aphid year. Predator movement and abundance were driven by aphid colonization in soybean, and syrphid and coccinellid abundance were 33-fold and 15-fold more abundant in the high compared to the low aphid year. Thus, our study revealed complementary effects of landscape heterogeneity on aphid suppression: a reduction of resource concentration associated with increased crop diversity and resulting in bottom-up effects during an outbreak, and an increase in landscape complementation associated with increased edge density and top-down control in a low aphid year. Increasing crop diversity seems a promising strategy to mitigate aphid outbreaks without compromising food production.

Fallow fields and hedgerows mediate enhanced arthropod predation and reduced herbivory on small scale intercropped maize farms – δ13C and δ15N stable isotope evidence

Fallow fields and hedgerows enhance agricultural landscape heterogeneity and boost predatory arthropod diversity, though there is little direct quantitative evidence of their value in mediating pest suppression. Here, stable isotope analyses were used to quantify the influence of fallow field presence, fallow size proportion of farms, hedgerow volume and hedgerow type, on arthropod pest consumption by six predatory taxa. Levels of herbivory by four arthropod taxa on three vegetation groups: maize, beans and non-crops – were also considered. This was achieved through mixing model analysis with δ13C and δ15N stable isotope to identify and estimate food-source proportions incorporated into tissues of arthropod consumers collected from ten maize farms intercropped with beans in western Kenya. Fallow fields’ presence supported predation on Lepidopteran herbivores by attracting predatory bugs and wasps, and mediated lower herbivory levels. Fallow size proportion corresponded to higher taxa-level predation by ants and spiders on phytophagous beetles, and overall increase in bean herbivory, but predicted no difference in maize or non-crop herbivory. Higher hedgerow volumes did not affect overall predation pressure, but supported increased bean herbivory by Lepidoptera, and lower maize consumption by Orthoptera. Exotic hedgerows supported highest wasp predation on Lepidoptera while spiders consumed significantly more Orthoptera and phytophagous beetle pests on indigenous-hedgerow farms. Similarly, exotic hedgerows corresponded to enhanced Lepidoptera bean herbivory while trophic linkage of maize and non-crops to pests overall, were stronger with indigenous hedgerows. Thus, in addition to thicker hedgerows, predatory spillover impacts of wasps, bugs and beetles can be enhanced with fallow presence and exotic hedgerows, and that of spiders and ants, with larger fallows. Overall, the choice, combination and application of farm habitat structural features to maximize predatory arthropods’ contributions to pest biocontrol requires knowledge of focal crops, dominant pest groups and their most important predators. The findings demonstrate that fallow fields and hedgerows are significant in supporting the biological component of integrated crop pest management.

Rows make the field: Winter wheat fields with manipulated crop architecture show potential for ecological intensification based on higher natural pest and weed seed control

Ecological intensification aims to reduce environmental costs of agricultural production by increasing biodiversity and using the associated ecosystem services instead of, or in combination with, external inputs, so that yields are maintained at high levels or increased. However, to date there are few measures available for which such benefits have already been demonstrated in the field.In this study, the seeding pattern in winter wheat fields was manipulated to create a diversified crop architecture consisting of ‘unsown-rows’ and ‘densely-sown-rows’ in treatment fields in comparison to ‘conventionally-sown-rows’ in control fields to assess whether (i) in-field structural and microclimatic conditions are more heterogeneous in fields with manipulated crop architecture compared to conventionally managed fields, (ii) a change in crop architecture is related to higher species richness, activity density and altered body size distribution of carabid communities, (iii) this in turn increases natural pest and weed seed control, but (iv) does not lead to yield loss.In-field structural and microclimatic conditions were more heterogeneous in treatment fields compared to control fields, which was associated with significantly increased body sizes of predatory carabids and a trend for increased predatory carabid species richness (in the ‘unsown-rows’ of treatment fields). These changes were related to significantly stronger pest suppression in the ‘densely-sown-rows’ of treatment fields compared to ‘conventionally-sown-rows’ in control fields, with 10 % higher experimental pest predation rates and 56 % reduced crop damage caused by cereal leaf beetles. Moreover, carabids known to consume weed seeds showed significantly higher activity densities in ‘unsown-rows’ compared to ‘conventionally-sown-rows’, which was related to significantly higher experimental weed seed predation in ‘densely-sown-rows’. Wheat yields were not significantly different in fields with or without manipulated crop architecture.The results suggest that the simple measure of manipulating the seeding pattern in winter wheat fields creates a diversified crop architecture, thereby promoting carabid diversity and altering their community composition and activity density such that important ecosystem services are increased without yield losses. Thus, beyond fostering biodiversity, this measure has, although not directly tested here, the potential for being used for ecological replacement of pesticides through enhanced ecosystem services without entailing agronomic and economic disadvantages such as land opportunity costs or increased workload.

Contrasting roles of landscape compositions on shaping functional traits of arthropod community in subtropical vegetable fields

Agricultural intensification and land use transformation are among the main driving forces of the unprecedented decline of biodiversity and ecosystem services in croplands. Trait-based approaches provide a unique framework to detect the potential mechanisms of how this intensification affects biodiversity and alter ecosystem services. However, the potential relationship between arthropod traits and various types of habitats is still poorly understood, especially in subtropical vegetable agroecosystems. Here, we conducted a trait-based approach to evaluate the variable roles of different habitats on functional trait diversity and the structure of the arthropod community in brassica vegetable crops. Twenty-three conventional cruciferous vegetables fields were sampled over two years in three regions in Fujian, China. We found that the increasing proportion of non-brassica vegetable plantations and water bodies negatively affected the functional diversity of arthropods, whereas forest and grassland habitats showed a positive correlation, indicating habitat filtering for certain traits or trait combinations. This study demonstrates the importance of landscape composition as an ecological filter for vegetable arthropod community, and identifies how the proportion of different habitats selected for or against specific functional traits. Our findings support that increasing forest and grassland areas adjacent to vegetable fields can play a vital role in promoting the functional diversity of arthropod communities. Since the natural enemy assemblages supported by these habitats bear combinations of diverse traits adapted to disturbance, they have the potential to enhance pest suppression in the highly variable environment of vegetable crops.

Flowering plants in open tomato greenhouses enhance pest suppression in conventional systems and reveal resource saturation for natural enemies in organic systems

Vegetable production in open greenhouses is often associated with high inputs of synthetic pesticides. Introducing flowering plants into such greenhouses may promote the top-down pest suppression by natural enemies and reduce the reliance on pesticide use. However, it is not known how effective this practice is in organically and conventionally managed greenhouse crops. We assessed the influence of introducing flowering plants into open greenhouses with organically and conventionally managed tomato crops on the abundance of pests, natural enemies (NE), pollinators, and crop yield. We monitored tomato crops during two years in two greenhouses at four organic farms and four conventional farms that used integrated pest management (IPM). On each farm one greenhouse contained flower islands of basil (Ocimum bacilicum), marigold (Tagetes patula) and alyssum (Lobularia maritima), and the other greenhouse served as a control. Organic farms had yields comparable to conventional farms, a lower abundance of pests, less pest injury, and a higher abundance of NE. The cumulative pest:NE ratio was 9 for organic and 38 for conventional management. The effect of introducing flowering plants on arthropods depended significantly on the type of farm management. Conventionally managed tomato crops in greenhouses with seven flower islands per 100 m2 had 18% lower pest abundance compared to the control greenhouses without flowers, while flower islands did not significantly influence arthropod abundances in organically managed tomato crops. Tomato plants had a higher abundance of pests than the three introduced plant species in conventionally managed greenhouses, while marigold had a higher abundance of pests than tomato in organically managed greenhouses. Alyssum supported a relatively low pest abundance and high abundance of NE and pollinators. Our findings indicate that NE in IPM-conventionally managed greenhouses can benefit from resources provided by flowering plants, resulting in reduced pest abundance, while in organically managed greenhouses the conditions are already favourable for the suppression of pests and addition of floral resources does not further improve the effectiveness of NE. This finding highlights the potential of agroecological and organic management to reduce the reliance on synthetic pesticides without yield reduction.

Immigration drives ship rat population irruptions in marginal high‐elevation habitat in response to pulsed resources

AbstractPest animal populations, such as rodents, often irrupt in response to pulsed resources. However, few studies have considered how understanding the propagation of irruptions across landscapes could lead to more efficient pest suppression. Resource pulses might create temporary source–sink dynamics in heterogeneous environments, whereby reservoirs of animals living in high‐quality habitat increase and spill over into more marginal habitat. Low‐density populations in marginal habitat could also increase through in situ breeding by residents in response to increased food availability. Understanding the relative importance of these two nonmutually exclusive processes is important as pest outbreaks could potentially be more efficiently controlled by targeting source populations early in an outbreak. We used a Bayesian hierarchical model to estimate the importance of density‐dependent emigration from lower elevation habitats versus in situ breeding by resident animals to the population growth of invasive ship rats (Rattus rattus) in marginal, high elevation habitats during a pulsed resource event (beech seed mast). We found that emigration from lower elevations was important for facilitating rapid population growth at high elevations, enabling rats to reach peak densities of 10.6 rats ha−1. Without immigration, rats were predicted to reach peak densities of only 1.8 rats ha−1 at high elevation, given their densities in that habitat when we started monitoring (0.6 rats ha−1). This result suggests that rat control that targets low and mid‐elevations only may be sufficient to suppress irruptions in high‐elevation habitat if control effectively prevents immigration. Our study suggests spillover from higher quality habitats may enable outbreaks to rapidly propagate over landscapes. However, for r‐selected taxa such as rodents, even very low densities of animals living in marginal habitats can increase significantly when resource pulses occur, albeit at lower densities than for populations in higher quality habitat.

Integrated Pest Management Of Field Crops

Insect pests, diseases, nematodes and weeds constitute major biotic stresses in crop production systems inflicting 15 to 25% or more yield losses. Adverse effects of pesticides can be countered through adoption of integrated pest management (IPM), which emphasizes harmonious use of safer and environment friendly methods of pest suppression. IPM works on the premise that all pest population levels are not injurious to crops. It is a knowledge intensive decision based activity and requires tools and techniques for its execution. IPM algorithm involves crop loss assessment, pest risk analysis, development of pest surveillance and forewarning methodology and decision support tools for harmonious integration of management tactics within the framework of Integrated Crop Management system. IPM modules for various field crops are based upon integration of resistant cultivars, cultural, mechanical and physical methods, natural enemies, biopesticides and pesticides to suppress pest population without jeopardizing the environment. Various organizations addressing the issue of plant health management need to converge in a mission mode to disseminate IPM throughout the country. This review covers the latest developments in these areas of IPM with main reference to India.

Fighting caterpillar pests and managing agricultural insecticide resistance with Lepidoptera-associated <i>Enterococcus casseliflavus</i>

<p>Probiotics are live microorganisms that are intended to benefit the health of metazoan hosts. Mutualism in insects (both pests and beneficial insects) provides a vital contribution to host fitness. With the development and demand for healthy modern agriculture, bacterial symbionts are considered to be an important toolbox for pest control and beneficial insect protection. <i>Enterococcus casseliflavus</i> is a widespread symbiont in most Lepidoptera insect pests. Recent studies indicated that <i>E. casseliflavus</i> provides beneficial phenotypes to the host, including supplying a diet lacking amino acids and enhancing insecticide resistance. We propose that <i>E. casseliflavus</i> should have enormous biotechnological potential awaiting further exploitation for Lepidoptera insect pest control or beneficial insect protection through symbiont-targeted insecticide resistance management, because this symbiont is widespread in natural caterpillar hosts, easily isolatable and cultured, and rapidly spreadable within the caterpillar population. We outline the rationales for why <i>E. casseliflavus</i> is suitable for application in pest management and envision possible plans of symbiont-targeted therapeutics via four potential approaches: genome modification, phage engineering, predatory biocontrol, and synthetic microbiome. This perspective opens up a grand blueprint for the future of symbiont-targeted insect pest suppression or economic insect promotion.</p>

Birds and bats enhance yields in Afrotropical cacao agroforests only under high tree-level shade cover

Central/West Africa is one of the most biodiverse regions on earth and one of the largest producers of cacao, producing about 68.4 % of the world's chocolate. Here, cacao pests and diseases can cause losses of $761 million annually. However, no studies from Africa have quantified the role of flying vertebrates as pest suppressors in cacao plantations. We used an exclusion experiment to prevent access of bats and birds to cacao trees for 12 months and quantified how their absence affected arthropod communities, herbivory, and cacao crop yield. Overall, important pests such as mealybugs and other hemipterans were more abundant in exclosures (9 and 1.6 times increase, respectively), despite potential multitrophic interactions with simultaneously increasing predatory arthropods such as spiders and mantis. Under heavy shade (90 %), cacao trees with flying vertebrate exclosures had 3.9 times fewer flowers and 3.2 times fewer large pods than control trees, corresponding to estimated losses on average of $478 ha−1y−1. Under low tree-level shade cover (10 %) however, the opposite pattern was evident: exclosure trees had 5.2 times more flowers and 3.7 times more large pods than control trees, corresponding to estimated savings on average of $796 ha−1y−1. We demonstrate that the enormous potential of African flying vertebrates as pest suppressors in cacao plantations is dependent on local shade tree management and only economically relevant above 50 % of shade. Despite higher productivity at low shade levels, our findings encourage African policymakers and farmers to adopt more high shade cacao agroforestry systems to maximize pest suppression services provided by bats and birds.

Co-existence of Pesticides and Fertilizers in Agricultural Soil Environment

Pesticides and fertilizers are of utmost importance in suppression of pests and meeting food requirements. However, the excessive and inefficient use has ended up in severe environmental damage, in which soil health has intensively witnessed most critical part of harmful problems. Exposure of pesticides and fertilizers adversely affects soil nutrient content, enzyme activities, predominant non-target organisms, structural and functional biodiversity of microbial populations. It has been observed that the adsorption-desorption, leaching and degradation behaviors of pesticides can be modified in response to fertilizers, which regulate microorganisms for assimilated pollutes. Application of optically pure, bio-based pesticides and fertilizers for soil amendment is a sustainable and low cost option to avoid combined contamination in the soil environment. The practices of organic wastes as cost-effective biochar loaded fertilizers can also further achieve a double win targets in the formation of green production mode for pesticides and fertilizers. Additionally, more studies are needed to help identify opportunities for new agro-ecosystem.

Economic benefits of conservation biocontrol: A spatially explicit bioeconomic model for insect pest management in agricultural landscapes

Spatially explicit population dynamic models have been successfully used to explore management scenarios in terms of pest suppression across a wide range of systems. However, the economic implications of pest management, particularly in the case of biological control and non-crop management strategies, have not been well considered. A bioeconomic spatially explicit simulation model was developed, that integrates models of pest population dynamics, pest movement and economics of management. The utility of the model is demonstrated here usingNysius vinitor, a pest of grain crops in Australia. The model estimates the short- and long-term economic benefits of three pest management strategies: (1) in-field pesticide spray; (2) pest suppression through weed management in non-crop habitat; and (3) bolstering biocontrol through revegetation with, or maintenance of, native vegetation. Across all management types, high yield and low relative management cost resulted in a greater chance of a gross profit. The impacts of the pests themselves were shown to be non-linear, with an intermediate level of pest pressure maximizing the economic gain from management. Pest dispersal capacity influenced the profitability of management of non-crop vegetation, with lower pest dispersal resulting in a greater likelihood of benefit, as benefits from non-crop management are localized (e.g., increased beneficial insect populations). In an intensively cropped landscape, pesticide management was most profitable over the short-term. Once a 10-year horizon was reached, then the profitability of revegetation was greater and continued to increase. While weeding requirements are low, it is likely to always be profitable in the long-term to maintain or restore native vegetation in good condition to control this pest in an intensively cropped landscape. Using pesticide alongside revegetation gave some short-term gain, but the negative impact of pesticide on beneficials outweighed the benefit and in the long-term it is less profitable. These results do not hold in a low production landscape, due to increased pest pressure and costs of managing non-crop habitat. In summary, when quantified over a 10–20 year time horizon, revegetation or conserving native remnants in good (i.e., non-weedy) condition could be economically more beneficial to control an insect pest than ongoing pesticide use, in intensively cropped landscapes.

Compatibility of biological control and pesticides mediated by arthropod movement behavior and field spatial scale

Integrated pest management programs frequently rely on a combination of pesticide use with cultural controls such as diversifying agroecosystems to control pest populations. Selective pesticides can impose both lethal and sublethal effects on natural enemies. However, understanding the compatibility of pesticide use with biological control strategies is critical for pest management success. The population dynamics of natural enemies subjected to the effects of pesticides, especially those that experience sublethal effects, is critical to this understanding. Although lethal effects of pesticides on natural enemies are well-studied, sublethal effects of pesticide exposure such as the impact on natural enemy movement is less well understood – especially across different habitat spatial scales. We present a simulation model using coupled partial differential equations to explore the sublethal effects of pesticide use, via reduced predator movement, on pest suppression across a gradient of farm spatial scales. Using a beetle-aphid model system, we find that in small fields, increased abundance of natural enemies can reduce the need for pesticide sprays. However, in mid-sized fields, we find that impaired predator mobility caused by pesticide sprays has a negative impact on biological control by the natural predator community. We also demonstrate how timing of predator introduction to a field can complement timing of pesticide sprays. We discuss the implications of these results for biological control planning and implementation.

The Relationship between Landscape Patterns and Populations of Asian Longhorned Beetles

The Asian longhorned beetle (ALB), Anoplophora glabripennis (Motschulsky), is one of the most harmful invasive alien species attacking hardwood trees. Increasing human activities have caused changes in the landscape patterns of ALB habitats, disrupting the habitat balance and weakening landscape-driven pest suppression. However, the relationship between landscape patterns (compositional and structural heterogeneity) and ALB populations has not been defined. In this study, we used remote sensing data to calculate landscape metrics and combined them with ground survey data. Using a multivariable linear regression model and a linear mixed model, we analyzed the relationship between landscape metrics and ALB populations and between forest stands attributes and ALB populations. The study results indicated that largest patch index (LPI), mean radius of gyration (GYRATE_MN), mean shape index (SHAPE_MN), and Shannon’s diversity index (SHDI) strongly influenced ALB populations at the landscape level. In addition, at the class level, only the forest class metrics LPI and aggregation index (AI) significantly impacted ALBs. The study also indicated that tree height (TH) and tree abundance (TREEAB) were good predictors of ALB populations.

The Suppressive Effects of Biochar on Above- and Belowground Plant Pathogens and Pests: A Review.

Soilborne pathogens and pests in agroecosystems are serious problems that limit crop yields. In line with the development of more ecologically sustainable agriculture, the possibility of using biochar to control pests has been increasingly investigated in recent years. This work provides a general overview of disease and pest suppression using biochar. We present an updated view of the literature from 2015 to 2022 based on 61 articles, including 117 experimental case studies. We evaluated how different biochar production feedstocks, pyrolysis temperatures, application rates, and the pathosystems studied affected disease and pest incidence. Fungal pathogens accounted for 55% of the case studies, followed by bacteria (15%), insects and nematodes (8%), oomycetes and viruses (6%), and only 2% parasitic plants. The most commonly studied belowground pathogen species were Fusarium oxysporum f. sp. radicis lycopersici in fungi, Ralstonia solanacearum in bacteria, and Phytophthora capisci in oomycetes, while the most commonly studied pest species were Meloidogyne incognita in nematodes, Epitrix fuscula in insects, and both Phelipanche aegyptiaca and Orobanche crenata in parasitic plants. Biochar showed suppression efficiencies of 86% for fungi, 100% for oomycetes, 100% for viruses, 96% for bacteria, and 50% for nematodes. Biochar was able to potentially control 20 fungal, 8 bacterial, and 2 viral plant pathogens covered by our review. Most studies used an application rate between 1% and 3%, a pyrolysis temperature between 500 °C and 600 °C, and a feedstock based on sawdust and wood waste. Several mechanisms have been proposed to explain disease suppression by biochar, including induction of systemic resistance, enhancement of rhizosphere competence of the microbial community, and sorption of phytotoxic compounds of plant and/or microbial origin. Overall, it is important to standardize biochar feedstock and the rate of application to improve the beneficial effects on plants in terms of disease control.

Response of the rice stem borer Chilo suppressalis (Walker) and its parasitoid assemblage to landscape composition

The rice stem borer (RSB), Chilo suppressalis (Walker), is an economically important pest of rice in subtropical Asia. Up till present, it remains unknown how pest abundance and parasitoid-mediated biological control are modulated by landscape composition. In this study, 20 rice fields with varying proportion of non-crop habitat in (2000 m radius) landscape sectors were selected in China’s Jiangxi province. RSB infestation levels were highest in agriculture-dominated landscapes. Meanwhile, parasitism rate increased with pest pressure but was not related to landscape-level non-crop habitat cover. Landscape-level responses of parasitoids were species-specific and likely modulated by functional traits. The specialist parasitoid Cotesia chilonis (Munakata) responded negatively to non-crop habitat, while positive responses were recorded for the generalists Eriborus sinicus (Holmgren) and Microgaster russata (Haliday). Our work unveils the occurrence of a bottom-up cascade in which spatiotemporal rice cropping patterns shape pest pressure and parasitism dynamics, with more diverse landscapes experiencing lower RSB infestation levels. Non-crop habitats within the landscape matrix equally retained parasitoid species with varying feeding modes and attack strategies. Hence, despite its (globally) inconsistent impacts on biological control, agricultural landscape diversification can directly benefit pest suppression and thus remains a valuable component of the ecological intensification toolbox.

New self-sexing Aedes aegypti strain eliminates barriers to scalable and sustainable vector control for governments and communities in dengue-prone environments.

For more than 60years, efforts to develop mating-based mosquito control technologies have largely failed to produce solutions that are both effective and scalable, keeping them out of reach of most governments and communities in disease-impacted regions globally. High pest suppression levels in trials have yet to fully translate into broad and effective Aedes aegypti control solutions. Two primary challenges to date-the need for complex sex-sorting to prevent female releases, and cumbersome processes for rearing and releasing male adult mosquitoes-present significant barriers for existing methods. As the host range of Aedes aegypti continues to advance into new geographies due to increasing globalisation and climate change, traditional chemical-based approaches are under mounting pressure from both more stringent regulatory processes and the ongoing development of insecticide resistance. It is no exaggeration to state that new tools, which are equal parts effective and scalable, are needed now more than ever. This paper describes the development and field evaluation of a new self-sexing strain of Aedes aegypti that has been designed to combine targeted vector suppression, operational simplicity, and cost-effectiveness for use in disease-prone regions. This conditional, self-limiting trait uses the sex-determination gene doublesex linked to the tetracycline-off genetic switch to cause complete female lethality in early larval development. With no female progeny survival, sex sorting is no longer required, eliminating the need for large-scale mosquito production facilities or physical sex-separation. In deployment operations, this translates to the ability to generate multiple generations of suppression for each mosquito released, while being entirely self-limiting. To evaluate these potential benefits, a field trial was carried out in densely-populated urban, dengue-prone neighbourhoods in Brazil, wherein the strain was able to suppress wild mosquito populations by up to 96%, demonstrating the utility of this self-sexing approach for biological vector control. In doing so, it has shown that such strains offer the critical components necessary to make these tools highly accessible, and thus they harbour the potential to transition mating-based approaches to effective and sustainable vector control tools that are within reach of governments and at-risk communities who may have only limited resources.