Ecosystem Service Of Pest Control Research Articles

Changes in arthropod communities mediate the effects of landscape composition and farm management on pest control ecosystem services in organically managed strawberry crops

Abstract Landscape composition and local diversification practices such as polyculture, cover cropping and hedgerows may promote natural pest control by benefiting natural enemy communities on farms. Our study employs piecewise structural equation modelling (PSEM) to test causal hypotheses regarding the effects of landscape composition and local diversification practices on arthropod communities and pest control ecosystem services. We sampled 27 organic strawberry fields in California's Central Coast region in 2015 and 2016 (17 repeated between years) for a total of 37 distinct sites across years. The sites were selected along orthogonal gradients of landscape composition and local diversification practices. We also investigated the effects of two common pest management practices. At each site, we sampled arthropod communities using a handheld vacuum and performed sentinel prey experiments using the pest species Lygus hesperus to estimate pest control levels. At the landscape scale, proportion of woody habitat increased natural enemy abundance; at the local scale, on‐farm diversification practices increased natural enemy diversity. Insecticides and tractor vacuuming, aimed at controlling pests, were indirectly detrimental to pest control services. Both practices decreased natural enemy abundance, and while insecticides also decreased pest abundance, vacuuming did not. Natural enemy abundance and diversity increased pest control levels, while pest abundance had the opposite effect. The PSEM results confirmed our hypotheses that landscape and local effects on pest control are mediated through changes in arthropod communities. Synthesis and applications. At the landscape scale, higher proportions of woody habitat are associated with greater natural enemy abundance, which increases pest control levels in organic strawberry crops. When promoting pest control ecosystem services is a policy goal, regional planners should prioritize the conservation and restoration of woodlands in agricultural landscapes. At the local scale, actions by individual growers can impact pest control services. For many growers, adopting practices that promote on‐farm plant diversity may be a feasible solution for increasing pest control levels while avoiding the environmental and economic costs imposed by insecticide application and tractor vacuuming.

Pest-removal services provided by birds on subsistence farms in south-eastern Nigeria.

To what extent birds provide the ecosystem service of pest control in subsistence farms, and how this service might depend on retained natural habitats near farmlands is unexplored in West Africa. To fill this knowledge gap, we placed plasticine mimics of insect pests on experimentally grown crops on the Mambilla Plateau, South Eastern Nigeria. We recorded bird attacks on the mimics and the proportion of mimics removed by birds. We also determined the influence of distance of crops from forest fragments on both attack and removal rates. We placed 90 potted plants of groundnut (Arachis hypogea) and bambara nut (Vigna subterranea) along 15 transects running 4.5 km from forest edge into open grassland. Each plant had six of the 540 mimics in total placed on their leaves. We inspected the potted plants weekly for 12 weeks to record (i) the presence of bird beak marks on mimics, and (ii) the number of missing mimics. Once a week we collected all the mimics from the plants and counted the number of assumed beak marks. After counting we replaced the mimics on the plants, mark free. We found a strong positive correlation between the abundance of insectivorous birds and the mean number of missing mimics and/or bird attack marks on mimics. However, this positive effect of insectivorous bird abundance on prey mimic attack/removal became less strong the farther they were from a forest fragment. We found increased predation rates and abundance of insectivorous birds closer to forest fragments. Our data suggest that pest predation may be a key ecosystem service provided by insectivorous birds on Nigerian farmlands. Farmlands that are closer to forest fragments may experience a higher rate of pest control by insectivorous birds than those further away, suggesting that retaining forest fragments in the landscape may enhance pest control services in sub-Saharan subsistence farms.

Spatial and genetic crop diversity support ecosystem service delivery: A case of yield and biocontrol in Dutch organic cabbage production

• We developed and validated a diagrammatic scale to assess herbivore leaf-feeding injury in cabbage. • We used an experimental network of seven intercropping designs. • Crop diversification via intercropping reduced herbivore feeding injury in cabbage. • Lower injury was observed with the presence of a within-field functional flower strip. • Individual and total yields were maintained in five out of seven intercropping designs. A single focus on yield in agroecosystems comes at the expense of other ecosystem services, for instance, biocontrol of pests. In this study, we investigated the potential of intercropping to improve the delivery of ecosystem services by cropping systems. Intercropping was expected to deliver a higher yield through facilitation and complementarity while simultaneously suppressing pests via pest habitat dilution and habitat provision for natural enemies. Utilizing a network of experiments on crop diversification with different spatial arrangements and different levels of genetic crop diversity across the Netherlands in 2018, we analyzed the effect of seven intercropping designs on crop injury by pests, yield and quality in cabbage. Individual cabbage leaf injury by herbivorous pests was assessed using a newly developed diagrammatic scale. Provisioning services were measured as individual cabbage fresh weight and yield per unit area. We found a significant negative relationship between crop diversity and herbivore feeding injury per cabbage: intercropping designs with more species, accessions and/or cultivars exhibited lower feeding injury. The presence of flower strips significantly reduced overall injury in the adjacent cabbage strip, despite higher injury found in the rows closer to the flower strip. There was no clear relationship between crop diversity and fresh marketable weight per cabbage, however five out of seven intercropping designs were able to maintain total yield per area when compared with the sole crop reference. Our results show that crop diversification can simultaneously support the production ecosystem service by maintaining fresh marketable weight per cabbage plant and productivity per unit area, as well as the regulating ecosystem service of pest control. These results provide a basis for redesigning large-scale arable fields into diversified productive systems, and thereby facilitate the transition towards more sustainable farming systems. A better understanding of crop functionality and management needs in diverse arrangements is relevant for such redesign.

Natural vegetation and bug abundance promote insectivorous bat activity in macadamia orchards, South Africa

Accelerating land use change is associated with the loss of species and their ecosystem services. South Africa is the world's largest producer of macadamias and the industry continues to grow. Insectivorous bat species are important for pest control, but bat populations are declining. Therefore, proactive management of bat communities in agricultural landscapes is essential. We acoustically monitored bats and used light traps to catch arthropods during one annual cycle, sampling five macadamia orchards monthly in Limpopo, South Africa. We used GIS and R to analyse both the general bat and foraging bat activity of the two main foraging guilds (open-air/clutter edge guild) in different land use types and total activity with respect to arthropod abundances. Overall clutter edge guild activity (number of passes) decreased with macadamia and orchard (all other fruit) cover in the high season and increased with bush cover and distance to settlements (potential roosts) in the low season. Open-air guild activity increased with fallow cover in the high season. Foraging activity (feeding buzzes) of the clutter edge guild increased with bush cover over the whole year. Total activity (both guilds) increased with abundance of true bugs, including the main macadamia pests, and bush cover.In conclusion, natural and semi-natural vegetation promote bat activity in macadamia orchards, and potentially bats' provision of the ecosystem service of pest control. In times of accelerating land use change, remnants of natural vegetation are important refuges and need to be maintained or restored. The installation of bathouses might further improve bat activity.

Temporal change in vegetation productivity in grain production landscapes: linking landscape complexity with pest and natural enemy communities

1. Strategies to enhance the ecosystem service of pest control in agricultural landscapes often rely on manipulating the structure of the landscape to reduce pest population build‐up or facilitate natural enemy activity. For highly mobile and polyphagous invertebrate pest species the agricultural landscape represents a continually changing mosaic of resources and habitats that at certain points in time may be conducive to high population productivity and therefore pest outbreaks. Deciding which features of the landscape we need to measure and monitor to understand this process is the first step in developing intervention strategies. Previous studies have focused on static measures of landscape composition and have generally ignored landscape configuration and change across time.2. In this study we sampled invertebrate pests and predatory natural enemies repeatedly over two years from crop, pasture and semi‐natural habitats (up to 36 sites per landscape) in multiple agricultural landscapes (14km diameter circles) across Australia's grain production regions. The temporal pattern in vegetation productivity was quantified (using remote‐sensed Normalized Differential Vegetation Index) at the landscape‐scale and related to the pest and natural enemy density data.3. Metrics derived from the vegetation show variation across time and highlight transition points in the landscape that might represent important shifts in resources for higher trophic levels. The landscape metrics that were related to pest density were different in each landscape, but generally characterized connectivity of vegetation classes (more than configuration or composition). How connected or dis‐aggregated vegetation productivity classes were appears important for pest dynamics in these landscapes.

Sharing enemies: evidence of forest contribution to natural enemy communities in crops, at different spatial scales

Abstract The increase in cultivated lands has led to ecosystem and biodiversity loss. Arthropod natural enemies, involved in the ecosystem service of biological control, benefit from non‐crop habitat and may be affected by its proximity and amount in the landscape. We have evaluated natural enemy richness and composition in relation to forest cover in the landscape and distance from the forest, for a Chaco Serrano forest‐soybean crop system. Forest contribution to natural enemies on soybean was also investigated, by assessing similarities between forest and crop assemblages, and examining body size of shared enemies in relation to distance from the forest. In nine landscape circles, yellow pan traps were placed in forest and soybean crops (5, 25, 50 and 100 m from forest edge), which collected 8041 specimens representing 290 species. Species richness of natural enemies was positively related to forest cover and declined from the forest to the furthermost soybean locations, with both forest cover and its proximity affecting community composition. Also, similarity of forest and crop assemblages increased with forest cover and proximity. Finally, forest‐crop shared assemblages showed larger average body size at greater distances from the forest, indicating dispersal limitations on forest contribution to the crop. Our results suggest that forest species are important components of natural enemy communities on soybean, and that both the amount of natural habitat and its proximity may influence agroecosystems. We emphasise the importance of non‐crop habitat to help maintain natural enemy communities and ensure the ecosystem service of pest control.

Habitat functionality for the ecosystem service of pest control: reproduction and feeding sites of pests and natural enemies

Landscape management for enhanced natural pest control requires knowledge of the ecological function of the habitats present in the landscape mosaic. However, little is known about which habitat types in agricultural landscapes function as reproduction habitats for arthropod pests and predators during different times of the year. We studied the arthropod assemblage on six crops and on the seven most abundant native plant species in two landscapes over 1 year in Australia. Densities of immature and adult stages of pests and their predators were assessed using beat sheet sampling. The native plants supported a significantly different arthropod assemblage than crops. Native plants had higher predator densities than crops over the course of the year, whereas crops supported higher pest densities than the native plants in two out of four seasonal sampling periods. Crops had higher densities of immature stages of pests than native plants in three of four seasonal sampling periods, implying that crops are more strongly associated with pest reproduction than native plants. Densities of immature predators, excluding spiders, were not different between native plants and crops. Spiders were, however, generally abundant and densities were higher on native plants than on crops but, because some species disperse when immature, there is less certainty in identifying their reproduction habitat. Because the predator to pest ratio on native plant species showed little variation, and spatial variation in arthropod assemblages was limited, the predator support function of native vegetation may be a general phenomenon. Incentives that maintain and restore native remnant vegetation can increase the predator to pest ratio at the landscape scale, which could enhance pest suppression in crops.

Seeds in farmland food-webs: Resource importance, distribution and the impacts of farm management

Whilst considerable research effort in Europe has linked agricultural intensification with dramatic declines of seed-feeding birds, surprisingly little is known about the wider importance of seeds in animal food-webs. Moreover, understanding the dynamics of farmland seed food resources for species of conservation concern is of considerable research interest.We examined the distribution of berries and soil-surface seeds in the managed and unmanaged habitats of a 125ha organic farm. We took soil suction-samples over a year, counted and identified all seeds, and compared abundances and species-richness between habitats. We constructed ecological networks from literature records and by rearing insects to investigate the importance of these seeds for insects, birds and mammals. We predicted the impacts of management on seed biomass, energy and the ecosystem service of pest control across the whole farm.We estimated seed and berry food resources of up to 33metric tons of biomass and 560GJ of energy on the farm. Potentially, more than 330 species use the seeds as a food resource, the overwhelming majority of which are invertebrates (82%) relying predominantly on non-crop and weed species. Generally, uncultivated semi-natural habitats such as woodland and mature hedgerows were more species-rich and had higher seed biomass and energy than crop habitats throughout the year, but fallow land was disproportionately important for seeds during the summer. Models of increased management intensity revealed declines of up to 19% in seed biomass and energy and cascades through the network that resulted in a substantial decrease in potentially pest-controlling parasitoids.

Do differences in food web structure between organic and conventional farms affect the ecosystem service of pest control?

While many studies have demonstrated that organic farms support greater levels of biodiversity, it is not known whether this translates into better provision of ecosystem services. Here we use a food-web approach to analyse the community structure and function at the whole-farm scale. Quantitative food webs from 10 replicate pairs of organic and conventional farms showed that organic farms have significantly more species at three trophic levels (plant, herbivore and parasitoid) and significantly different network structure. Herbivores on organic farms were attacked by more parasitoid species on organic farms than on conventional farms. However, differences in network structure did not translate into differences in robustness to simulated species loss and we found no difference in percentage parasitism (natural pest control) across a variety of host species. Furthermore, a manipulative field experiment demonstrated that the higher species richness of parasitoids on the organic farms did not increase mortality of a novel herbivore used to bioassay ecosystem service. The explanation for these differences is likely to include inherent differences in management strategies and landscape structure between the two farming systems.

Enhanced pest control in cabbage crops near forest in The Netherlands

Landscapes are composed of a multitude of habitat types which, potentially, can influence natural enemy populations. The contribution of specific habitat types to sustaining natural enemy populations in agricultural landscapes and the associated ecosystem service of pest control is not well understood. We investigated how landscape composition affected parasitism rates in 22 organic Brussels sprout fields in The Netherlands. Second and third instar larvae of Plutella xylostella were placed on experimental Brussels sprout plants in Brussels sprout fields and were recovered after two days in the field. Parasitism rates ranged between 4 and 94% and were related to landscape variables at a scale of 0.3, 1, 2 and 10 km. Univariate analysis using a generalized linear mixed model indicated that parasitism rates were positively related with area of forests at a scale of 1, 2 and 10 km, forest edges at a scale of 1 and 2 km and road verges at a scale of 1 km. Forest and road verges are likely to provide food and alternative hosts for parasitoids and are less disturbed habitats than agricultural fields. These results suggest that forests and road verges may play an important role in sustaining effective densities of parasitoids of P. xylostella in agricultural landscapes.