Conservation Biological Control Research Articles

Volatile chemical cues emitted by an agricultural companion plant (Cnidium monnieri) attract predatory lacewings (Chrysoperla sinica)

Plant volatiles play an important role in the recruitment of arthropod natural enemies and are widely used in foraging by many species. Therefore, identification of plants that release useful volatile organic compounds (VOCs) for influencing natural enemies and for the control of pests can be helpful in conservation biological control. Cnidium monnieri (L.) can convene many predatory enemies (lady beetles, hoverflies, lacewings) as a functional plant. The Chrysoperla sinica (Tjeder) is a dominant generalist predator, and can control the population of various pests in agricultural fields. However, how C. monnier recruits C. sinica and the chemical association between them is unknown. In this study, we tested the attractiveness of odor released by flowers and leaves of C. monnieri to C. sinica in Y-tube olfactometer. Next, we conducted solid phase microextraction (SPME), gas chromatography-mass spectrometry (GC–MS), and electrophysiological studies (EAG) to analyze the compounds and identified the volatile components which have effects on C. sinica. We also used a Y-tube olfactometer to verify the effectiveness of the volatile components on C. sinica under laboratory conditions. In olfactometer trials, C. sinica adults preferred flowers compared with leaves and fresh air. In GC–MS and electroantennography trials, seventy-six volatiles extracted from C. monnieri, twelve antenna-active components in three different concentrations (0.1 μg/mL, 1 μg/mL, 10 μg/mL) were detected for electroantennography. In the last behavioral identification assays, four synthetic compounds (10 μg/mL) had significant attractiveness of adult C. sinica antenna (i.e., γ-terpinene, trans-β-Ocimene, nerolidol, (Z)-3-Hexen-1-ol). These studies suggest that there is a chemical association between natural enemies C. sinica and the functional plant C. monnieri. This study provides a basis that can facilitate the production and application of attracting natural enemy and development and application of enhancing attractants.

Status and trends of biological control research, extension, and education in the United States

Abstract The number of public-sector biological control scientists and practitioners in the United States was determined by a survey conducted in 2019. A total of 344 personnel were identified in 49 states and Washington DC; 218 employed by universities, 86 by the federal government and 36 by state departments of agriculture. There were 10-34 personnel in eight states, 6-9 in 11, and 0-5 in 31, overall averaging less than 50% of their combined effort on biological control. Applications for biological control agents included about 30% for row crops and vegetables; 12% each for orchards, urban landscapes, outdoor ornamentals, and forests; and 22% for the remainder. The federal government provided an average of 42% of the funding for university, federal, and state biological control research and extension. The states contributed 29-35%, commodity groups supplied 19-24%, and the remaining funds were from private sources. Of 54 universities in the United States, 18 conducted in-person classroom education and training in biological control, with seven offering courses via distance. However, another 18 universities had discontinued their comprehensive courses. Biological control instruction was incorporated into courses and workshops on integrated pest management and sustainable agriculture at 50 universities. Correspondingly, during the past 24 years, biological control has gradually developed from primarily an independent discipline to increasingly being part of integrated pest management. Classical, augmentative and conservation biological control have nevertheless remained distinguishable high priority subdisciplines. Funding continues to be essential for advancing biological control, requiring societal understanding and acceptance. Advancement of biological control in the United States will require increased investment in personnel and their education and training, along with delivery of effective pest management technologies.

Chemical and visual stimuli for conservation biological control of stink bugs in soybean: potential use and flaws on egg parasitoid recruitment

Chemical and visual stimuli for conservation biological control of stink bugs in soybean: potential use and flaws on egg parasitoid recruitment

The indirect effect of nectar-inhabiting yeasts on olfactory responses and longevity of two stink bug egg parasitoids

AbstractAdult parasitoids are well known to feed on sugar-rich resources such as floral nectar. Recently, an increasing body of evidence has shown that nectar is ubiquitously colonized by microorganisms and, as a consequence, microbial metabolic activity can affect several traits of floral nectar. Yet, how the fermentation of nectar by yeasts impacts the olfactory responses and performance of parasitoids is largely understudied, especially in the case of egg parasitoids. In this study, we investigated whether fermentation by the nectar yeasts Metschnikowia gruessii and M. reukaufii affects the olfactory responses of Trissolcus basalis and Ooencyrtus telenomicida, two egg parasitoid species associated with the southern green stink bug Nezara viridula. We also investigated how yeast fermentation affects the longevity and survival of the egg parasitoids. Results of static four-chamber olfactometer tests showed that nectar fermented by M. gruessii (but not by M. reukaufii) was attractive to both egg parasitoid species, whereas no significant yeast-mediated effects were found in terms of wasp longevity. Gas chromatography coupled with mass spectrometry (GC-MS) showed a clear separation of the volatile profiles among M. gruessii, M. reukaufii and non-fermented control nectar supporting the results of the insect bioassays. The results of our study highlight the need to consider the role of microbes when studying interactions between flower nectar and egg parasitoids and could have implications from a conservation biological control perspective.

Crop species diversity levels with attract and reward strategies to enhance Pieris brassicae parasitism rate by Cotesia glomerata in strip intercropping

Abstract Crop diversification through inter‐ and mixed cropping practices has been shown to enhance conservation biological control of herbivorous pest insects. However, distinct cropping practices are usually tested independently, which makes assessing the relative impact of specific measures difficult. We assessed parasitism rates of released large cabbage white (Pieris brassicae) caterpillars by parasitoids on white cabbage (Brassica oleracea) plants in six different cropping systems: four different strip‐cropping designs, a pixel cropping design and a monoculture. These cropping designs differed in the number of crops included, the use of parasitoid‐attractive cultivars in concurrence with a cash cultivar, the use of nectar‐providing crops for adult parasitoids and the spatial arrangement of the crops. Parasitism rate by the main P. brassicae parasitoid Cotesia glomerata was enhanced by strip cropping of white cabbage with wheat, and even further enhanced by the inclusion of four more main crops. Contrastingly, C. glomerata parasitism rate was lower in the most intensive crop mixture, that is pixel cropping, than in any of the strip‐cropping designs. The use of attractive cultivars or rewarding floral resources within a strip‐cropping set‐up did not significantly further enhance C. glomerata parasitism rate. Synthesis and applications: Our results show that increasing the number of crops in the agroecosystem enhances parasitism rates, whereas the additional inclusion of more subtle measures to attract or reward parasitoids shows mostly marginal effects. We argue that strip cropping can readily be employed as (part of a) pest control strategy, but trait‐based measures still need further development. How to implement attract and/or reward strategies in large‐scale agricultural systems should be further evaluated in the context of crop diversification schemes. Read the free Plain Language Summary for this article on the Journal blog.

Natural regulation of Helicoverpa armigera larvae by hymenopteran parasitoids in northern Cameroon: Is there scope for application of conservation biological control in cotton agroecosystems?

The conservation biological control (CBC) concept has been explored through research conducted in northern Cameroon on larval parasitism of Helicoverpa armigera, a major cotton pest, on different host plants year round, from early September 2008 to late December 2014. A total of 47,152 caterpillars were reared over the 6-year period. They were found regularly present on crops such as cotton and okra and on wild plants, including Corynandra viscosa and Hyptis spp. The overall percentages of nematode- and disease-infected caterpillars were very low (1.05% and 2.92%, respectively). Diptera species accounted for less than 0.1% of the parasitoids that had emerged from caterpillars. Total hymenopteran parasitism was 10.5%, and varied markedly depending on the host plants. Nine Hymenoptera species were identified, with Meteorus laphygmarum being the dominant one (almost 80% of all 2698 adult parasitoids obtained after rearing), followed by Schoenlandella variegata (16.42%) and Charops spinitarsis (<2%). Out of this total, 35%, 28% and 25% of the adults were obtained respectively on C. vicosa, cotton and Hyptis spp., i.e. < 5% on all other host plants. The analysis conducted on 237 collections showed that, after adjusting for year and month effects, a highly significant difference was found between the parasitism rates observed on the different host plant species. The plants most suitable for H. armigera parasitism were Acantospermum hispidum, C. viscosa and Hyptis spp. The proportion of M. laphygmarum among emerged hymenoptera was highest on C. viscosa, medium on cotton and Hyptis spp. and lowest on L. esculentum. Future studies that could be carried out are outlined in the discussion with the aim of facilitating the transfer of parasitoids from caterpillars present on one plant species to those infesting cotton crops.

Habitat heterogeneity reduces abundance of invasive mealybugs in subtropical fruit crops

Abstract The simplification of agricultural landscapes has been associated with an increase in pest pressure. While monocultures increase the resources available for pests and may facilitate their dispersion, the lack of non‐crop habitats may reduce the resources available for pest natural enemies. Herein, we tested which of these hypotheses, namely ‘resource concentration’ and ‘natural enemies’, can better explain the abundance of invasive mealybug pests in two subtropical fruit crops. For this aim, 17 persimmon orchards and 16 citrus orchards were sampled during three different seasons across two consecutive years. Using a model selection approach, we assessed the effects of the surrounding landscape (proportion of focal crops and semi‐natural habitats at different distances) and inter‐row ground cover vegetation on the abundance of mealybugs and their natural enemies. The proportion of focal crop in the landscape increased the abundance of mealybugs attacking both crops. This effect was found at closer distances (up to ~600 m) in citrus and at both closer and further distances (up to 1250 m) in persimmon. Non‐crop habitats, both surrounding semi‐natural habitats and ground cover vegetation, decreased the abundance of mealybugs by increasing the activity of their parasitoids in persimmon. Conversely, non‐crop habitats did not decrease the abundance of the main mealybug species attacking citrus, likely because this mealybug species was not attacked by native or naturalized parasitoids. Synthesis and applications. Our models show that the increase in habitat heterogeneity at local and landscape scales can reduce the abundance of invasive mealybugs in subtropical crops via ‘resource concentration’ and ‘natural enemies’ mechanisms. Therefore, habitat diversification strategies should be considered in the conservation biological control of invasive mealybugs. Importantly, our findings also show that the presence of efficient natural enemies is critical to maximize their control through habitat diversification strategies.

Entomopathogens in the integrated management of forest insects: from science to practice.

The most important aim of the integrated management of forest insect pests remains the prevention of insect outbreaks, which are a consequence of the interaction of many factors in forest ecosystems, including species composition, age and health of the forest, soil type, the presence of natural enemies, and climatic factors. Integrated pest management until now has been achieved using measures aimed at shaping the functioning of stands in a changing environment. The aim of this review is to summarize research on the use of entomopathogens (microorganisms and nematodes) in the management of forest insect pests and to identify the principal knowledge gaps. We briefly describe the main research directions on the use of pathogens and nematodes to control insect pests and discuss limitations affecting their implementation. Research on entomopathogens for the biocontrol of forest insects has provided a wealth of knowledge that can be used effectively to reduce insect populations. Despite this, few entomopathogens are currently used in integrated pest management in forestry. They are applied in inoculation or inundation biocontrol strategies. While the use of entomopathogens in forest pest management shows great promise, practical implementation remains a distant goal. Consequently, sustainable reduction of forest pests, mainly native species, will be largely based on conservation biological control, which aims to modify the environment to favor the activity of natural enemies that regulate pest populations. This type of biocontrol can be supported by a range of silvicultural measures to increase the resilience of stands to insect infestations. © 2023 Society of Chemical Industry.

Toxicity of Pesticides Applied in European Vineyards on Anagyrus vladimiri and Trichogramma evanescens, Parasitoids of Planococcus ficus and Lobesia botrana.

Risk assessments of chemical pesticides toward natural enemies are crucial for ensuring sustainable grapevine-integrated pest management. In this context, laboratory experiments were conducted to evaluate the toxicity of four insecticides (lambda-cyhalothrin, flupyradifurone, acetamiprid, and cyantraniliprole) and one fungicide (spiroxamine) commonly applied in German (European) vineyards on the pupae and adults of both Anagyrus vladimiri, a parasitoid of the vine mealybug Planococcus ficus, and Trichogramma evanescens, a parasitoid of the European grapevine moth, Lobesia botrana. The tested pesticides did not significantly affect the development of the pupal stage inside mealybug mummies or the emergence of the parasitoid A. vladimiri. The pesticides flupyradifurone, acetamiprid, and spiroxamine resulted in the highest mortality percentages for all emerged A. vladimiri parasitoids at 8 and 10 days after treatment compared with either in lambda-cyhalothrin or cyantraniliprole. However, all pesticides, except the diamide insecticide cyantraniliprole, significantly affected the development of the pupal stage and the emergence of the parasitoid T. evanescens. The percentages of T. evanescens emergence following the application of the fungicide spiroxamine or either lambda-cyhalothrin or flupyradifurone were significantly higher than those observed in the acetamiprid treatment. Regarding direct contact toxicity, the highest percentages (100%) of A. vladimiri adult parasitoid mortality were obtained in the flupyradifurone, acetamiprid, and spiroxamine treatments, while the lowest mortality percentages were observed in lambda-cyhalothrin, cyantraniliprole, and untreated control treatments. According to the IOBC classes of toxicity, flupyradifurone, acetamiprid, and spiroxamine were classified as harmful, while both lambda-cyhalothrin and cyantraniliprole were classified as slightly harmful to A. vladimiri adults. As such, all pesticides had a significant impact on the survival of exposed T. evanescens adults. The highest percentages of adult T. evanescens mortality were obtained in the flupyradifurone, acetamiprid, and spiroxamine treatments, with the fungicide spiroxamine resulting in significantly higher mortality percentages than either flupyradifurone or acetamiprid, while the lowest mortality percentages were found in the lambda-cyhalothrin and cyantraniliprole treatments. Therefore, applying the insecticides acetamiprid and/or flupyradifurone and the fungicide spiroxamine should be avoided when A. vladimiri and/or T. evanescens are naturally present or released in grapes. The insights gained from these two easy-to-rear parasitoid species allow analogous conclusions to be drawn for closely related species in vineyards belonging to either family Encyrtidae or Trichogrammatidae, which are not easy to rear. Interestingly, using the safer insecticides lambda-cyhalothrin and/or cyantraniliprole could be compatible with both parasitoid species, which could be sustainably exploited in either conservation or augmentative biological control in vineyards.

Impacts of landscape heterogeneity on bottom-up effects affecting biological control

Conservation biological control of crop pests by natural enemies relies on management strategies to favour their trophic interactions. In agricultural landscapes, natural enemies acting across habitat boundaries may feed on non-pest prey, resulting in apparent competition between non-pest prey and pests. Such communities, including pests, non-pest prey, and natural enemies have been shown to be affected by landscape heterogeneity depending on the dispersal capacity of the interacting organisms. Nonetheless, a mechanistic understanding of how natural enemies’ dispersal capacity interacts with landscape heterogeneity affecting conservation biological control is, however, lacking. Here, we contribute to such mechanistic understanding through modelling. We simulated the consequences of differences in landscape heterogeneity defined by the contrast of plant resource distribution in a semi-natural habitat compared to a crop and variation in natural enemy dispersal capacity on biological control of a pest. Our model showed that variation in plant resource distribution resulted in bottom-up effects that led to shifts in the dominant mechanism underlying biological control. At high landscape heterogeneity when resources differ strongly between crop and the semi-natural habitat, non-pest prey benefitted from the plant resources available, promoting apparent-competition-mediated biocontrol for high-dispersing natural enemies. At low landscape heterogeneity, pests benefitted mostly from plant resources available, promoting direct plant-pest-enemy mediated biocontrol. Interestingly, intermediate levels of landscape heterogeneity resulted in the lowest levels of biocontrol. Our results highlight the importance of potential bottom-up effects that the matching between plant resources available in a habitat and the resource preference of herbivores can induce on conservation biological control.

Enhancing Coccinella Beetle Biological Pest Control via a Floral Approach in Cucumber Greenhouse.

Flower-rich habitats are crucial for promoting biodiversity and ecosystem services within agricultural ecosystems, such as pollination and pest control. The present study investigates the efficacy of employing floral structures as a criterion for the selection of plant species in order to enhance the attraction of natural enemies within cucumber greenhouses, consequently augmenting floral resources. The results of our study provide evidence that flower strips have a beneficial effect on the fitness of critical natural predators, while not facilitating the proliferation of detrimental insect species. These findings exhibit potential for enhancing pest-management services in the agricultural sector. The findings of our study demonstrate that pest levels within greenhouse environments closely resemble those observed in real-world commercial cropping systems. As a result, the introduction of Coccinella septempunctata and Menochilus sexmaculatus biocontrol agents is confirmed to be a reliable and efficient method for pest management. The phenomenon of predator-prey density dependency is recognized as a crucial element in the implementation of biological control strategies. Furthermore, we investigate the impact of floral resources on the reproductive capacity of indigenous predators. The impact of Coriandrum sativum on fertility is substantial, indicating that the presence of a varied plant assortment with overlapping flowering periods can prolong the availability of floral resources. This study highlights the significance of flower-rich habitats and deliberate plant selection in augmenting biodiversity, ecosystem services, and pest management within agricultural settings. The implementation of conservation biological control technologies presents supplementary ecological advantages, thus offering practical implications for the promotion of sustainable agricultural practices.

Providing water sources to insectivorous bats for conservation biological control in arid date plantations

Balance between the high demand for agricultural production and the negative environmental impact of intensive agriculture requires the development of sustainable agricultural approaches. One such approach is conservation biological control (CBC), which aims at enhancing pest suppression by using natural enemies, such as predators and parasites. Insectivorous bats are considered as potential natural enemies for CBC of insect agricultural pests. Bats drink from open water sources and forage above them, hence we hypothesized that supplementation of artificial water pools adjacent to desert date plantations might promote the activity and species richness of insectivorous bats in this habitat, thereby contributing to pest suppression. We predicted that bats will be more attracted to the pools during summer, when other water sources are scarce, than during spring. In addition, we explored the effect of water supplements on the desert bat community structure. Eight pools were installed in a date plantation in the hyper-arid Arava valley, Israel. Bats were acoustically monitored during three experimental stages: 1) before filling the pools with water; 2) while the pools held water and 3) after emptying them. The lesser date moth (Batrachedra amydraula), a major date pest, was monitored using pheromone traps in parallel with the experimental stages. We found that the pools increased bat activity in summer, but not in spring, while species richness was not affected in either season. The local bat community structure was significantly altered while the pools held water, but not due to increased activity of synanthropic Mediterranean species at the expense of local desert species. The number of individuals of the lesser date moth near the pools decreased with the increase in bat activity. Our results support the idea that seasonal water supplementation enhances bat activity in arid farmlands with potential contribution to pest control and the actual contribution to pest suppression should be further quantified. We suggest that the integration of small artificial pools to promote agricultural pest predation by bats may help reduce crop loss and potentially contribute to the conservation of desert bat communities by adding water sources.

Pollen as sole food source for two generalist predatory mite species (Acari: Phytoseiidae)

Amblyseius largoensis and Typhlodromus ornatus (Acari: Phytoseiidae) are generalist predatory mites that naturally inhabit coconut plantations and other tropical crops. We assessed the suitability of two coconut pest mites, Raoiella indica (Acari: Tenuipalpidae) and Aceria guerreronis (Acari: Eriophyidae); the storage mite Tyrophagus putrescentiae (Acari: Acaridae); honey; and the pollens of castor bean, Ricinus communis, and cattail, Typha domingensis, and their mixture, as food sources for the mass rearing of A. largoensis and T. ornatus. Both pollens, supplied singly or mixed, generated the highest progeny production by both A. largoensis and T. ornatus, and were therefore selected for further life table studies. The pollen diets did not influence the survival of A. largoensis whereas there was higher survivorship of T. ornatus fed on the mixed pollen diet than on R. communis pollen alone. The maximum oviposition rate of both A. largoensis and T. ornatus occurred at the beginning of adulthood, irrespective of the pollen diet. Overall, the life table parameters indicated that the pollen of R. communis for A. largoensis, and R. communis with the mixed pollen diet for T. ornatus, were the best regarding population growth and reproduction. Collectively, our results indicate that A. largoensis and T. ornatus can survive and reproduce excellently when fed solely on R. communis or on the mixed pollen diet. In addition, these results point to the potential of pollen supplementation for the enhancement of the efficiency of these predators in conservation biological control.

Chemical ecology in conservation biocontrol: new perspectives for plant protection.

Threats to food security require novel sustainable agriculture practices to manage insect pests. One strategy is conservation biological control (CBC), which relies on pest control services provided by local populations of arthropod natural enemies. Research has explored manipulative use of chemical information from plants and insects that act as attractant cues for natural enemies (predators and parasitoids) and repellents of pests. In this review, we reflect on past strategies using chemical ecology in CBC, such as herbivore-induced plant volatiles and the push-pull technique, and propose future directions, including leveraging induced plant defenses in crop plants, repellent insect-based signaling, and genetically engineered crops. Further, we discuss how climate change may disrupt CBC and stress the importance of context dependency and yield outcomes.

The double-edged sword effect of warming on the soil predatory mite Cosmolaelaps brevistilis (Karg, 1978) (Mesostigmata: Laelapidae)

In this study we used the average annual temperature in Brazil and four warming predictions to propose a maximum thermal threshold for the predatory mite Cosmolaelaps brevistilis (Karg, 1978) (Mesostigmata: Laelapidae) as an experimental model. Then, we evaluated the effects of warming on the biological parameters of C. brevistilis for conservation biological control. We observed higher rates of oviposition and predation of the prey Tyrophagus putrescentiae (Schrank, 1781) (Astigmatina: Acaridae) under warmer conditions at 75 ± 10% RH. The highest rates of prey consumption and oviposition were observed at 28°C compared to the others tested (22, 24, and 26°C). However, the egg viability of C. brevistilis was reduced at the same temperature. Therefore, temperature increases both positive and negative effects on the biological parameters of C. brevistilis which are important for the ecological interactions that are essential for biological control programs.

Effect of Cabbage and Basil intercropping on conservative biological control of Aphids

Conservative biological control seeks to preserve beneficial organisms as the natural enemies of pests through habitat management. These studies aimed to measure the potential of basil (Ocimum basilicum L.) in the biological control of aphids in green cabbage (Brassica oleraceae L. var. acephala); and to evaluate the influence of the intercropping on green cabbage productivity. In an organic commercial crop of green cabbage in Águas Claras, RS, basil was used as an associated border (BB) and contrasted with plants in beds with no border (WB). We compared Aphididae density and parasitism, in the spring/summer seasons of 2016 and autumn/winter of 2017. Brevicoryne brassicae L. and Myzus persicae Sulzer (Hemiptera, Aphididae) were recorded in the green cabbage, in 2016. A mean of 13.8 ± 8.72 aphids/leaf was recorded in the WB, significantly higher than in the BB, 3.4 ± 1.83 (Tukey 5% p = 0.00002). In the 2017 season, this difference was not significant at 10.3 ± 12.73 (WB) and 6.9 ± 11.34 (BB). The mean of parasitized aphids was 2.8 ± 2.84 in WB and 9.9 ± 2.87 BB (p = 0.0041) in the spring crop and 2.9 ± 4.10 (WB) and 14.25 ± 7.3 (BB) in the winter (p = 0.0039). The association of green cabbage and basil had an area equivalence index (AEI) in 2016 = 1.07 and 2017 = 0.99 indicating that basil did not affect green cabbage yield.

Life history studies of stink bugs: much-needed research to support their conservation biological control

Life history studies of stink bugs: much-needed research to support their conservation biological control

Seasonal density and natural mortality of Halyomorpha halys (Stål) and indigenous stink bugs (Hemiptera: Pentatomidae) in a field crop agroecosystem.

Stink bugs (Hemiptera: Pentatomidae), including the exotic Halyomorpha halys (Stål), Nezara viridula (L.), and other indigenous species, are pests that damage a variety of agricultural crops. At a study site in the southeastern United States, we measured the density of stink bug species and patterns of parasitism and predation on corn, cotton, and soybean and host trees in an adjacent woodline. We assessed parasitism and predation of naturally laid egg masses in crops and sentinel egg masses in host trees and used pheromone-baited traps to determine H. halys seasonal development. Overall, H. halys and N. viridula were the dominant bugs observed. Adult H. halys were first detected each year on trees, followed by corn, and then cotton and soybean, suggesting that trees served as a source of H. halys dispersing into crops. For H. halys, more nymphs were captured in soybean than in corn or cotton. For N. viridula, more adults were captured in corn and cotton than in soybean, and more nymphs were captured in corn during 2019 and 2021 than in 2020. Percentage parasitism of N. viridula egg masses (74.2%) was higher than than that for H. halys egg masses (54.3%). Accordingly, conservation biological control has the potential to enhance parasitism of indigenous stink bugs and H. halys in field crop agroecosystems.

Macro-scale perspectives in conservation biological control: latitudinal differences in the effects of organic farming on insect pests and natural enemies in rice paddy ecosystems

The pest control services provided by natural enemies are important for maintaining crop productivity in environmentally friendly agriculture with reduced use of pesticides. Organic farming is generally considered to increase the abundance of natural enemies and to enhance ecosystem services, but species and guild compositions vary from region to region, and so the population levels of pests and their natural enemies can be expected to vary geographically. Here, we surveyed the abundance of rice insect pests and spiders as their natural enemies in 51 organic and 45 conventional paddy fields at 22 locations in Japan and examined latitudinal differences in the effects of farming practices on their abundance. Independently of latitudinal differences, organic farming had positive effects on the abundance and species diversity of spiders caught in nets and on Tetragnatha and lycosid spiders. It increased the abundances of the leafhopper Nephotettix cincticeps and the white-backed planthopper Sogatella furcifera, and decreased that of the small brown planthopper Laodelphax striatellus. Both spiders and insect pests showed diverse responses to the interaction between farming practice and latitude. In particular, insect pests distributed in warmer regions, such as So. furcifera and Ne. cincticeps, tended to be more abundant in the south. The ratios of spider to pest abundance, as indicators of pest suppression, were lowest in organic paddies at lower latitudes for So. furcifera and Ne. cincticeps; at higher latitudes they were higher in organic paddies than in conventional paddies for La. striatellus. These results suggest that the effectiveness of pest suppression by natural predators in organic paddy fields varies by region depending on the ecological characteristics of each organism. As such, it is necessary to devise field management strategies appropriate to each region to balance crop production and biodiversity.

Enhancing arthropod communities through plant diversified edge of kale cultivation

Plant diversification can increase organism abundance while reducing phytophagous insect activity in agricultural crops. We assessed arthropod diversity in fava beans (Vicia faba), fennel (Foeniculum vulgare), and marigolds (Tagetes patula) along the periphery of a kale plantation and examined the influence of their proximity to the kale cultivation. The study took place at the Centro Estadual de Diagnóstico e Pesquisa Florestal, Santa Maria, RS, Brazil. We collected plant samples from the periphery and cultivated kale plants at three distances from the edge: within two meters, 10 to 12 meters, and 20 to 22 meters. We recorded the number and biomass of marketable leaves from three harvests. A total of 618 arthropods were collected from plants along the periphery: Insecta (589), Arachnida (20), and Entognatha (9). Hemiptera was the most prevalent order (49.84%). Kale plants near the periphery experienced less predation from leaf beetles. Plants along the periphery hosted important predator groups as well as phytophages that can serve as alternative prey. Diversifying the periphery with fennel, fava bean, and marigolds shows promise as a strategy to enhance the arthropod community in kale cultivation, thereby acting as a conservative biological control.