Hibernation of predatory arthropods in semi-natural habitats

Non-crop habitats provide important resources for natural enemies. Many natural enemies hibernate in non-crop habitats, from which they may colonise arable fields in the spring. Spring colonisation ensures annual repopulation of the crop with natural enemies, allowing them to keep pace with the development of pest populations. The availability of non-crop habitats can, therefore, be crucial to successful conservation biological control. We quantified the density of overwintering natural enemies near organic Brussels sprout crops in five different non-crop habitats (short grassy field margin, herbaceous field margin, herbaceous field margin under a tree line, ditch and forest). Soil and litter samples of non-crop habitats were taken at two sites. One site was located in an open agricultural landscape, the other in a landscape dominated by mixed forest. Insects belonging to Staphylinidae, Araneae, Carabidae, Coccinellidae and Dermaptera were the most abundant. Mean densities of predatory arthropods were higher in the open agricultural landscape (290 predators m⁻²) than in the forested landscape (137 predators m⁻²). Herbaceous habitat types supported the highest densities of overwintering predators (up to 400 predators m⁻²), whereas densities in the forest were lowest (10 predators m⁻²). These results indicate that herbaceous non-crop habitats are important refugia for predators and may play a vital role in conservation biological control. Handling Editor: Arne Janssen.     

A simple criterion for successful biological control on annual crops

Population dynamics of pest insect-natural enemy systems on annual crops is quite different from those seen in classic biological control programes. On an annual crop, for example, the persistence of populations of pest insects is forced to terminate when crops are harvested. Pest control on annual crops aims to suppress the maximum density of the pest below a certain level, and a low level equilibrium is not always the aim. It is important to determine the initial impact just after release of a natural enemy in order to determine the success of a biological control program. Therefore, effectiveness of natural enemies should be evaluated by prediction of such short-term population dynamics. This paper presents a new and simple analytical model for successful biological control on annual crops. A criterion of successful biological control is given as the ratio of the pest and natural enemy populations just when the pest begins to decrease. This ratio is derived from the intrinsic rates of natural increase of both populations and the daily total predation by natural enemies. Using this model, criteria on appropriate number and time of release of natural enemies are obtained. The practical applications of this model are discussed with respect to evaluating the success or failure of natural enemy releases in future biological control programs.     

Evaluation of pest control efficiencies for different banker plant systems with a simple predator–prey model

The banker plant system has been introduced for the biological control of various pest species in Japanese greenhouses. With the banker plant system, non-crop plants infested with a host insect (a non-commercial crop pest) are placed in the greenhouse to provide alternative resources for the parasitoids or predators. We want to evaluate the effectiveness for controlling pests on the crop in a quantitative way by immigrating predators from the banker plant. Therefore, we developed a simple model for the interaction of the pest and predator in the crop and included the banker plant only as a source for predators. For three different pest-predator systems we parameterised the model and used these models to predict under what conditions biological control in a banker plant system is successful. We defined successful as keeping the pest below the economic injury level of the crop estimated from damage analysis. Because the crop is mostly grown during a period that lasts less than a year our analysis should not only focus on the equilibrium dynamics. In contrast, it should also focus on the transient dynamics. Our main analytical result, from the equilibrium analysis, is that for successful control the maximum lifetime consumption of immigrating predators should exceed the daily prey growth at half the value of the maximum consumption rate. For practical purpose this translates into the fact that the immigration of predators at a low initial pest density is crucial for successful control.     

Biological control of Myzus persicae (Hemiptera: Aphididae) through banker plant system in protected crops

Banker plants with Aphidius colemani were tested in greenhouse for control of Myzus persicae on arugula and sweet pepper crops and compared to inoculative releases of parasitoids. Banker plants system consisted of pots of oat (non-crop plant) infested with Rhopalosiphum padi (non-pest herbivore). The non-pest herbivore serves as an alternative host for A. colemani (parasitoid of the target crop pest). In the arugula crop significant differences in the pest population between the two strategies of biological control showed the lowest densities of the pest when introducing the banker plant system. In the sweet pepper crop, there was no difference in the pest population between the two strategies of biological control.     

Habitat linkages in conservation biological control: Lessons from the land–water interface

Terrestrial landscapes, including those with embedded agroecosystems, are a mosaic of cover types varying in size. Creating or maintaining habitats that support natural enemy populations to combat agricultural pests is the primary method of conservation biological control. Non-crop habitats can be managed in an attempt to maximize the exchange of natural enemies with adjacent agroecosystems with the expectation that they will suppress damaging pest outbreaks. Despite this goal, current habitat management relying on natural enemy spillover into crops has been unreliably effective at reducing pest abundance or increasing crop yield. Furthermore, the expansion and intensification of agriculture and changes in global climate patterns threaten the foundations of conservation biological control in future agroecosystems. However, the aquatic–terrestrial interface offers a natural boundary similar to the one between agroecosystems and their neighboring non-crop habitats that can provide useful insights to the challenges facing growers. Research of the exchanges between water and land suggests general biological and physical processes that govern the movement of organisms between disparate habitats. We propose that like aquatic insects moving from water to land, natural enemy dispersal from non-crop donor habitats into recipient crop patches on the landscape is a function of (1) the production of natural enemies in the source habitat which establishes the abundance of organisms that can disperse, (2) how and why mobile natural enemies disperse themselves into neighboring recipient habitats, and (3) the configuration of donor and recipient habitats on the landscape. We suggest that conservation biological control practitioners can focus on these main components of natural enemy production and dispersal to predict the effectiveness of conservation biological control measures and guide their adaptation to future global change.     

Enhancing predator efficiency,the recent advances

Abstract

Three biocontrol methods include classical biological control, augmentation and conservation (CBC). Among them, CBC includes different agricultural compatible methods, which try to build up natural enemy populations and consequently improve biological control. Some of the most common conservation methods include providing shelter (e.g. beetle banks and hedgerows), supplementary foods (pollen and nectar), providing overwintering sites, increasing landscape biodiversity and nesting. Furthermore, cover crops, living mulches, which buffer the harsh environmental conditions, strip harvesting are among the other most common methods. Recently, genetic manipulation of predators has been considered as a potential strategy in biological control. This strategy aimed to manipulate beneficial genetically to more tolerant them against adverse effect of pesticides and environmental condition or increase their predation (parasitism rate). We tried to review a growing body of conservation studies focusing on practices promoting predator efficacy and performance. We will discuss how CBC practices contribute to improve pest control.     

Functional Invertebrate Prey Groups Reflect Dietary Responses to Phenology and Farming Activity and Pest Control Services in Three Sympatric Species of Aerially Foraging Insectivorous Birds

Farming activity severely impacts the invertebrate food resources of farmland birds, with direct mortality to populations of above-ground arthropods thorough mechanical damage during crop harvests. In this study we assessed the effects of phenological periods, including the timing of harvest, on the composition and biomass of prey consumed by three species of aerial insectivorous birds. Common Swifts Apus apus, Barn Swallows Hirundo rustica and House Martins Delichon urbica breed sympatrically and most of their diet is obtained from agricultural sources of invertebrate prey, especially from oil-seed rape crops. We categorized invertebrate prey into six functional groups, including oil-seed rape pests; pests of other arable crops; other crop-provisioned taxa; coprophilous taxa; and taxa living in non-crop and mixed crop/non-crop habitats. Seasonality impacted functional groups differently, but the general direction of change (increase/decrease) of all groups was consistent as indexed by prey composition of the three aerial insectivores studied here. After the oil-seed rape crop harvest (mid July), all three species exhibited a dietary shift from oil-seed rape insect pests to other aerial invertebrate prey groups. However, Common Switfts also consumed a relative large quantity of oil-seed rape insect pests in the late summer (August), suggesting that they could reduce pest insect emigration beyond the host plant/crop. Since these aerially foraging insectivorous birds operate in specific conditions and feed on specific pest resources unavailable to foliage/ground foraging avian predators, our results suggest that in some crops like oil-seed rape cultivations, the potential integration of the insectivory of aerial foraging birds into pest management schemes might provide economic benefits. We advise further research into the origin of airborne insects and the role of aerial insectivores as agents of the biological control of crop insect pests, especially the determination of depredation rates and the cascading effects of insectivory on crop damage and yield.     

Insect pest management in the age of synthetic biology

Arthropod crop pests are responsible for 20% of global annual crop losses, a figure predicted to increase in a changing climate where the ranges of numerous species are projected to expand. At the same time, many insect species are beneficial, acting as pollinators and predators of pest species. For thousands of years, humans have used increasingly sophisticated chemical formulations to control insect pests but, as the scale of agriculture expanded to meet the needs of the global population, concerns about the negative impacts of agricultural practices on biodiversity have grown. While biological solutions, such as biological control agents and pheromones, have previously had relatively minor roles in pest management, biotechnology has opened the door to numerous new approaches for controlling insect pests. In this review, we look at how advances in synthetic biology and biotechnology are providing new options for pest control. We discuss emerging technologies for engineering resistant crops and insect populations and examine advances in biomanufacturing that are enabling the production of new products for pest control.     

农田非作物生境调控与害虫综合治理

就害虫综合治理的研究而言,农田生态系统可以区分出作物生境和邻近作物的非作物生境。昆虫从作物生境迁移到非作物生境,与作物生境缺乏食物或受人类栽培活动干扰而引起的自然迁移、转换寄主和寻求庇护场所有关。许多研究表明,与特定作物田块相联系的植被类型和结构可影响害虫及其天敌迁居的种类、数量和时间。因此,我们可以通过改变大田周围非作物生境的植被组成及特征来调控农业生态系统中害虫与天敌的相互关系,提高天敌对害虫的控制效能。由于景观的空间格局对节肢动物的生物学特性有直接或间接的影响,所以,以景观为单元要比以同类作物的田块为单元更加适于害虫综合治理的研究和实施。在现代农业景观区域内重新引入和相嵌一些非栽培植物或廊道,可为众多有益节肢动物的繁殖、取食和避害提供多种类型的非作物栖境。     

Plant damage to vegetable crops by zoophytophagous mirid predators

The use of plant-feeding predators for biological pest control has traditionally been neglected, mainly due to the risk of them feeding on crop plants and causing economically significant damage. Yet, these predators offer advantages for biological pest control. They are mostly generalist predators that have an impact on several crop pests. They may also be able to establish on crops early in the growing season, when pests colonize them, and can remain on the target crop when prey is scarce. Therefore, management programs must seek to minimize risks while maximizing benefits. In vegetable crops, most of the literature on zoophytophagous predators has focused on four species: Dicyphus tamaninii, Dicyphus hesperus, Macrolophus pygmaeus and Nesidiocoris tenuis (Heteroptera, Miridae). The capacity of these species to produce crop damage in tomatoes varies. This damage has been related to relative predator-to-prey abundance, with damage increasing at high predator abundances and low prey densities. In this review, we analyze the use of these species in biological control programs and the associated benefits and risks. The differences in the damage caused by the four predatory species examined could not be attributed to either stylet morphology or saliva composition. However, feeding on specific plant structures where they may find the resources required for their development is what probably determines feeding damage. Understanding when and why these predators increase their feeding on plants or on certain plant parts is of crucial importance for integrating them in biological control programs.     

More pests but less pesticide applications: Ambivalent effect of landscape complexity on conservation biological control

In agricultural landscapes, the amount and organization of crops and semi-natural habitats (SNH) have the potential to promote a bundle of ecosystem services due to their influence on ecological community at multiple spatio-temporal scales. SNH are relatively undisturbed and are often source of complementary resources and refuges, therefore supporting more diverse and abundant natural pest enemies. However, the nexus of SNH proportion and organization with pest suppression is not trivial. It is thus crucial to understand how the behavior of pest and natural enemy species, the underlying landscape structure, and their interaction, may influence conservation biological control (CBC). Here, we develop a generative stochastic landscape model to simulate realistic agricultural landscape compositions and configurations of fields and linear elements. Generated landscapes are used as spatial support over which we simulate a spatially explicit predator-prey dynamic model. We find that increased SNH presence boosts predator populations by sustaining high predator density that regulates and keeps pest density below the pesticide application threshold. However, predator presence over all the landscape helps to stabilize the pest population by keeping it under this threshold, which tends to increase pest density at the landscape scale. In addition, the joint effect of SNH presence and predator dispersal ability among hedge and field interface results in a stronger pest regulation, which also limits pest growth. Considering properties of both fields and linear elements, such as local structure and geometric features, provides deeper insights for pest regulation; for example, hedge presence at crop field boundaries clearly strengthens CBC. Our results highlight that the integration of species behaviors and traits with landscape structure at multiple scales is necessary to provide useful insights for CBC.     

Effects of crop species richness on pest-natural enemy systems based on an experimental model system using a microlandscape

The relationship between crop richness and predator-prey interactions as they relate to pest-natural enemy systems is a very important topic in ecology and greatly affects biological control services. The effects of crop arrangement on predator-prey interactions have received much attention as the basis for pest population management. To explore the internal mechanisms and factors driving the relationship between crop richness and pest population management, we designed an experimental model system of a microlandscape that included 50 plots and five treatments. Each treatment had 10 repetitions in each year from 2007 to 2010. The results showed that the biomass of pests and their natural enemies increased with increasing crop biomass and decreased with decreasing crop biomass; however, the effects of plant biomass on the pest and natural enemy biomass were not significant. The relationship between adjacent trophic levels was significant (such as pests and their natural enemies or crops and pests), whereas non-adjacent trophic levels (crops and natural enemies) did not significantly interact with each other. The ratio of natural enemy/pest biomass was the highest in the areas of four crop species that had the best biological control service. Having either low or high crop species richness did not enhance the pest population management service and lead to loss of biological control. Although the resource concentration hypothesis was not well supported by our results, high crop species richness could suppress the pest population, indicating that crop species richness could enhance biological control services. These results could be applied in habitat management aimed at biological control, provide the theoretical basis for agricultural landscape design, and also suggest new methods for integrated pest management.     

Sustainable pest regulation in agricultural landscapes: a review on landscape composition, biodiversity and natural pest control

Agricultural intensification has resulted in a simplification of agricultural landscapes by the expansion of agricultural land, enlargement of field size and removal of non-crop habitat. These changes are considered to be an important cause of the rapid decline in farmland biodiversity, with the remaining biodiversity concentrated in field edges and non-crop habitats. The simplification of landscape composition and the decline of biodiversity may affect the functioning of natural pest control because non-crop habitats provide requisites for a broad spectrum of natural enemies, and the exchange of natural enemies between crop and non-crop habitats is likely to be diminished in landscapes dominated by arable cropland. In this review, we test the hypothesis that natural pest control is enhanced in complex patchy landscapes with a high proportion of non-crop habitats as compared to simple large-scale landscapes with little associated non-crop habitat. In 74% and 45% of the studies reviewed, respectively, natural enemy populations were higher and pest pressure lower in complex landscapes versus simple landscapes. Landscape-driven pest suppression may result in lower crop injury, although this has rarely been documented. Enhanced natural enemy activity was associated with herbaceous habitats in 80% of the cases (e.g. fallows, field margins), and somewhat less often with wooded habitats (71%) and landscape patchiness (70%). The similar contributions of these landscape factors suggest that all are equally important in enhancing natural enemy populations. We conclude that diversified landscapes hold most potential for the conservation of biodiversity and sustaining the pest control function.     

Constraints to the implementation of biological control in Sri Lanka

Sri Lanka is a tropical island with a rich diversity of arthropods, with many species of indigenous natural enemies of economic pests. However, no extensive island wide surveys have been carried out for natural enemies of major crop ecosystems and only a few of the indigenous natural enemies are reported useful for augmentation biological pest control by massive field releases of laboratory-produced insects. Most successful biological control programs on the island are importation (i.e. classical) biological control programs, where established exotic natural enemies control certain pest populations in valuable crops. There is growing interest in the use of native natural enemies in pest management, thus creating a need for intensive research on the ecology of indigenous natural enemies and development of infrastructure and technology to produce natural enemies for augmentation. This paper examines constraints and opportunities for implementation of biological control in Sri Lanka.     

Biocontrol of Pests of Apples and Pears in Northern and Central Europe - 3. Predators

Predators of apple and pear pests in northern and central Europe and their use as biological control agents are reviewed. Many natural enemy species are specialized feeders and are able to respond to the population dynamics of particular pest species. The most oustandingly successful example of this is the use of phytoseiid mites, particularly Typhlodromus pyri , against phytophagous pest mites in apple. This mite management strategy is now widespread throughout European apple growing regions. Another example is the use of Anthocoris nemoralis against pear psyllids, Cacopsylla pyricola and C. pyri . Several groups of naturally occurring polyphagous predators, such as chrysopids, coccinellids, syrphids and spiders, also prey on a number of pest species in orchards, contributing generally to the reduction in pest populations. However, they are unlikely alone to prevent pest damage fully and reliably. In seeking biological control opportunities for a particular pest, these polyphagous natural enemies are unlikely to be a high priority. An exception, due to its abundance in orchards, is the common earwig, Forficula auricularia , although this predator may also cause some fruit injury. Another option to consider when reviewing possibilities for biological control in orchards is the introduction of biological control agents. The success rate of this approach, using arthropod predators to control pests of field crops, has been generally poor. Furthermore, mass production methods for predators are likely to be difficult and very costly. The biological supplies industry is constantly seeking culture techniques, largely for arthropod biological control agents of pests of protected crops. It is possible that some future advance may be relevant to orchards, though currently available predators do not appear promising. A careful economic appraisal of the feasibility of use of any potential biological control agent would be prudent before embarking on research.     

Wildflower companion plants increase pest parasitation and yield in cabbage fields: Experimental demonstration and call for caution

Monocultures typical of intensive agriculture offer ideal conditions to specialized herbivores while depriving their natural enemies of habitat and nutritional resources. The resulting release of herbivores from both bottom-up and top-down control causes pest outbreaks in economically important crops. Boosting locally occurring natural enemy populations through species-specific habitat management to restore natural herbivore control has been much advocated but remains rarely tested in the field. Here, we investigated whether adding specifically selected flowering plants to monocultures increases parasitation rates of herbivores and crop yield. We performed replicated field experiments in 2 years and found that adding cornflowers (Centaurea cyanus) into cabbage (Brassica oleracea) fields significantly increased larval and egg parasitation and egg predation of the herbivore, reduced herbivory rates, and increased crop biomass in at least 1 year. These findings show that addition of a single, well-chosen flowering plant species can significantly increase natural top-down pest control in monocultures but success is variable. This is relevant on two applied levels. First, well chosen companion plants may partially substitute pesticides in agriculture if the approach is optimized, reducing negative effects such as unspecific killing of non-target organisms, residues in food, contamination of soils and water-bodies and increasing pesticide resistances. Our results suggest that, from an agro-economical point of view, egg parasitoids or predators may be the best targets for habitat management because strong natural selection acts on larval parasitoids to keep their hosts alive for their own development. Second, the addition of non-crop vegetation to monocultures benefits biodiversity conservation directly through resource diversification and indirectly through the reduction of pesticide application that increased natural control makes possible.     

High effectiveness of tailored flower strips in reducing pests and crop plant damage

Providing key resources to animals may enhance both their biodiversity and the ecosystem services they provide. We examined the performance of annual flower strips targeted at the promotion of natural pest control in winter wheat. Flower strips were experimentally sown along 10 winter wheat fields across a gradient of landscape complexity (i.e. proportion non-crop area within 750 m around focal fields) and compared with 15 fields with wheat control strips. We found strong reductions in cereal leaf beetle (CLB) density (larvae: 40%; adults of the second generation: 53%) and plant damage caused by CLB (61%) in fields with flower strips compared with control fields. Natural enemies of CLB were strongly increased in flower strips and in part also in adjacent wheat fields. Flower strip effects on natural enemies, pests and crop damage were largely independent of landscape complexity (8–75% non-crop area). Our study demonstrates a high effectiveness of annual flower strips in promoting pest control, reducing CLB pest levels below the economic threshold. Hence, the studied flower strip offers a viable alternative to insecticides. This highlights the high potential of tailored agri-environment schemes to contribute to ecological intensification and may encourage more farmers to adopt such schemes.     

Tea: Biological control of insect and mite pests in China

Tea is one of the most economically important crops in China. To secure its production and quality, biological control measures within the context of integrated pest management (IPM) has been widely popularized in China. IMP programs also provide better control of arthropod pests on tea with less chemical insecticide usage and minimal impact on the environment. More than 1100 species of natural enemies including about 80 species of viruses, 40 species of fungi, 240 species of parasitoids and 600 species of predators, as well as several species of bacteria have been recorded in tea ecosystems in China. Biological and ecological characteristics of some dominant natural enemies have been well documented. Several viral, bacterial, and fungal insecticides have been commercially utilized at large scale in China. Progress in biological control methods in conjunction with other pest control approaches for tea insect pest management is reviewed in this article. Knowledge gaps and future directions for tea pest management are also discussed.     

The effects of non-crop habitat on spotted wing drosophila (Drosophila suzukii) abundance in fruit systems: A meta-analysis

1. Drosophila suzukii (SWD) poses a threat to soft and stone fruit globally. SWD inhabits non-crop areas adjacent to farms from where it moves into crops to cause damage. Effective IPM control strategies, considering both the crop and non-crop area, are needed to control this economically important pest.
2. We conducted a meta-analysis to quantify the impacts of different non-crop habitats around fruit farms on SWD populations, comparing abundance of SWD trapped in crop and non-crop habitats.
3. Overall, SWD abundance was greater in non-crop habitats than in cropped areas and this difference was greatest in farms adjacent to woodland, or field margins containing known SWD host plants.
4. The difference in SWD abundance between crop and non-crop habitats was not affected by crop type but was greatest in the winter months and in conventional compared to organic farms, indicating conventional approaches can reduce relative SWD abundance.
5. Drosophila suzukii overwinter in non-crop habitats which provide refuge outside the cropping season. However, certain habitats support greater relative abundance of SWD than others and this is also affected by farm management. We discuss what these findings mean for effective control of SWD.

     

Review: predatory soil mites as biocontrol agents of above- and below-ground plant pests

Biological pest control is becoming increasingly important for sustainable agriculture. Although many species of natural enemies are already being used commercially, efficient biological control of various pests is still lacking, and there is a need for more biocontrol agents. In this review, we focus on predatory soil mites, their role as natural enemies, and their biocontrol potential, mainly in vegetable and ornamental crops, with an emphasis on greenhouse systems. These predators are still underrepresented in biological control, but have several advantages compared to predators living on above-ground plant parts. For example, predatory soil mites are often easy and affordable to mass rear, as most of them are generalist predators, which also means that they may be used against various pests and can survive periods of pest scarcity by feeding on alternative prey or food. Many of them can also endure unfavourable conditions, making it easier for them to establish in various crops. Based on the current literature, we show that they have potential to control a variety of pests, both in greenhouses and in the field. However, more research is needed to fully understand and appreciate their potential as biocontrol agents. We review and discuss several methods to increase their efficiency, such as supplying them with alternative food and changing soil/litter structure to enable persistence of their populations. We conclude that predatory soil mites deserve more attention in future studies to increase their application in agricultural crops.