Aphid Pests Research Articles

Landscape Complexity has Mixed Effects on an Invasive Aphid and Its Natural Enemies in Sorghum Agroecosystems.

Landscapes with more complex composition and configuration are generally expected to enhance natural enemy densities and pest suppression. To evaluate this hypothesis for an invasive aphid pest of sorghum, Melanaphis sorghi Theobald (Hemiptera: Aphididae), sampling in sorghum fields for aphids and natural enemies was conducted over two years in a southern U.S. coastal production region. Landscape composition and configuration of crop and noncrop elements were assessed using correlation and multivariate regression modeling to detect relationships with insects at different spatial scales. Significant models found more complex landscape configuration, particularly the amount of habitat edges, was associated with increased aphid and natural enemy abundance. Composition associated with noncrop habitats had the opposite effect. Numerical response of natural enemies was taxa dependent, with parasitism lower as landscape complexity increased, while predator numerical response was not affected by landscape complexity. These results indicate landscape complexity may increase both aphid and natural enemy abundance, but with decreasing parasitism and little association with predator numerical response. These relationships are likely contingent on overall environmental suitability to aphid population increase as results were less evident in the second year when average aphid abundance regularly exceeded the economic threshold. This study supports the importance of configuration, especially habitat borders, as a critical metric for determining pest-natural enemy dynamics within a large-scale cereal agroecosystem.

Effect of a cover crop on the aphid incidence is not explained by increased top-down regulation.

BackgroundCover crops can be used as a habitat management strategy to enhance the natural enemies and their temporal synchronization with a target pest. We examined the effect of winter oat intercropping within organic plum orchards on the natural enemy abundance and seasonal dynamics on the biological control of plum aphids in spring in Central Chile.MethodsWe compared the incidence and abundance of natural enemies and aphid pests from winter to the end of spring using two treatments: (1) plum trees with an oat cover crop (OCC) and (2) plum trees without a cover crop but with spontaneous vegetation (SV). We hypothesized that cover crops allow the development of winter cereal aphids, promoting the early arrival of natural enemies in spring, resulting in an earlier control of plum aphids.ResultsWinter cereal aphids developed well on the OCC, and as a result, a lower plum aphid incidence in spring was observed when compared to the SV. However, the abundance of natural enemies and the parasitism rates cannot explain the positive impacts of the oat cover crop on the aphid populations as there were no differences between treatments. A potential effect of the oat due to chemical and/or physical stimuli (bottom-up effects) could help to explain these results.

Field margins and botanical insecticides enhance Lablab purpureus yield by reducing aphid pests and supporting natural enemies.

Botanical insecticides offer an environmentally benign insect pest management option for field crops with reduced impacts on natural enemies of pests and pollinators while botanically rich field margins can augment their abundance. Here, we evaluated the non‐target effects on natural enemies and pest control efficacy on bean aphids in Lablab of three neem‐ and pyrethrum‐based botanical insecticides (Pyerin75EC®, Nimbecidine® and Pyeneem 20EC®) and determine the influence of florally rich field margin vegetation on the recovery of beneficial insects after treatment. The botanical insecticides were applied at the early and late vegetative growth stages. Data were collected on aphids (abundance, damage severity and percent incidence) and natural enemy (abundance) both at pre‐spraying and post‐spraying alongside Lablab bean yield. The efficacy of botanical insecticides was similar to a synthetic pesticide control and reduced aphid abundance by 88% compared with the untreated control. However, the number of natural enemies was 34% higher in botanical insecticide‐treated plots than in plots treated with synthetic insecticide indicating that plant‐based treatments were less harmful to beneficial insects. The presence of field margin vegetation increased further the number of parasitic wasps and tachinid flies by 16% and 20%, respectively. This indicated that non‐crop habitats can enhance recovery in beneficial insect populations and that botanical insecticides integrate effectively with conservation biological control strategies. Higher grain yields of 2.55–3.04 and 2.95–3.23 t/ha were recorded for both botanical insecticide and synthetic insecticide in the presence of florally enhanced field margins in consecutive cropping seasons. Overall, these data demonstrated that commercial botanical insecticides together with florally rich field margins offer an integrated, environmentally benign and sustainable alternative to synthetic insecticides for insect pest management and increased productivity of the orphan crop legume, Lablab.

CeO2 nanohybrid as a synergist for insecticide resistance management

Agricultural applications of nanomaterials, such as nanofertilizers, nanopreservation technologies, nanopesticides, and plant nanosensors, have recently attracted much attention. Herein, the CeO2-based nanohybrid MON@CeO2 was designed as a reactive oxygen species (ROS) inhibitor to effectively improve the susceptibility of insect pests to insecticides. MON@CeO2 was fabricated by intercalating CeO2 into mesoporous organosilica nanoparticles (MONs). The obtained MON@CeO2 showed a regular spherical shape with an average particle size of 45.4 nm, good monodispersity, and a negative surface charge (-14.6 mV). Bioassay results showed that MON@CeO2 significantly enhanced the toxicity (more than 2-fold) of nitenpyram, sulfoxaflor, and clothianidin against laboratory insecticide-resistant and field strains of Nilaparvata lugens. In particular, MON@CeO2 orchestrated host detoxification metabolism via downregulating ROS-dependent P450 gene expression, thus reducing host detoxification enzyme activities to overcome insecticide resistance. Furthermore, MON@CeO2 restrained host insecticide resistance in the notorious agricultural pests Aphis gossypii, Spodoptera frugiperda, and Sogatella furcifera. Therefore, MON@CeO2 could be used as a broad-spectrum nanosynergist against insecticide resistance, which would be a novel strategy for sustainable pest management.

A great little ally: revealing the morphology of the immature stages of the aphid pest predator Sphaerophoria rueppellii (Wiedemann, 1830) (Diptera: Syrphidae)

Morphology, at both adult and larval stages is crucial for the correct identification of an insect and a better understanding of its biology and behaviour. The lack of morpho-functional information in insects is much more general in the immature stages than in adults, and major insect orders, such as Diptera are no exception. Syrphids (Diptera: Syrphidae) include various genera with aphidophagous larvae playing a key role in the control of pest insects in both natural and agricultural systems. The aphidophagous Sphaerophoria rueppellii (Wiedemann, 1830) is a syrphid widely distributed in the Palearctic Region and it is of commercial importance as a biological control agent against aphid pests. However, little is known about the fine morphology of its immature stages because it was described in 1939, when microscopy did not allow detailed studies of certain morphological features. In this work, stereomicroscope and scanning electron microscopy (SEM) were used to get a deeper and more detailed picture of the immature stage morphology of this syrphid. SEM was used to examine in detail the chaetotaxy of three larval instars, the larva/puparium posterior respiratory process (PRP), and the chorionic structure of the egg. We describe for the first time the egg, first and second larval stages, and also give a complete updated description of the third-stage larva and the puparium. The three larval instars vary from each other, especially in the number of sensillae, PRP form, colour, and body size. The thickness of both the egg chorion and puparium integument were also measured. A possible interpretation of the reasons for the variability in the number of sensillae is discussed. Illustrations and full descriptions are provided for the egg, larva, and puparium of S. rueppellii, including the head skeleton of the third larval stage.

Glandular trichomes affect mobility and predatory behavior of two aphid predators on medicinal cannabis

Medicinal cannabis (Cannabis sativa L.) is a growing agro-industrial sector with the end product required to be free of pesticides. C. sativa is covered by specialized hairs called trichomes, namely, two types of non-glandular and three types of glandular trichomes. Despite the great importance of biological pest control in medicinal cannabis little is known about the impact of cannabis trichomes on natural enemies mobility and their interaction with prey. In the current study, by employing a video recording set-up, we determined the mobility of Aphidoletes aphidimyza and Chrysoperla carnea larvae and their interaction with the aphid pests Phorodon cannabis and Aphis gossypii on C. sativa leaf disks and inflorescences. As benchmark, we tested the same parameters on sweet pepper leaf disks, a benign host plant for both predators, and without trichomes. It was found, that A. aphidimyza females readily oviposited on P. cannabis colonies developing on C. sativa plants. On C. sativa leaves, covered by non-glandular trichomes, the larvae of both predators were able to move and prey upon aphids. On C. sativa inflorescences, where glandular trichomes prevailed, the larvae of A. aphidimyza were generally inactive while the C. carnea larvae were still able to move and interact with prey albeit to a lesser degree compared to the cannabis leaves. We suggest that the use of A. aphidimyza and C. carnea in augmentative biological control programs in medicinal cannabis should depend on the croṕs growth stage; the former should be employed during the vegetative while the latter during the vegetative and flowering crop stages.

Soil‐dwelling Bacillus spp. affects aphid infestation of calabrese and natural enemy responses in a context‐specific manner

Abstract Plant growth‐promoting rhizobacteria in the genus Bacillus have been shown to reduce growth and increase parasitism of some aphids, but the generality of these interactions is unknown. All previous studies have taken place in temperate conditions. We studied the effects of seed application of three Bacillus species, singly and in mixture, on three aphid pests and their natural enemies, on field‐grown calabrese (green sprouting broccoli) in the subtropical climate of South West India. All three bacteria reduced populations of Brevicoryne brassicae and Myzus persicae, but had no effect on numbers of Lipaphis erysimi. Chewing insects (flea beetles and diamondback moth larvae) were also unaffected by the treatments. However, parasitism rates of aphids were higher on plants treated with the bacteria. We conclude that Bacillus spp. shape above ground interactions in a context‐specific manner, directly via altered field infestations of some pests and indirectly via natural enemy responses.

When Does the Prey/Predator Ratio Work for the Effective Biocontrol of Cotton Aphid on Cotton Seedlings?

Simple SummaryCotton aphid (Aphis gossypii Glover) (Homoptera: Aphididae) is a major pest of cotton and other cash crops across cotton-growing areas in China. The decision to spray insecticide or rely on biocontrol and delay spraying is often a dilemma in cotton-growing regions. In this study, we used a laboratory experiment and a caged experiment in a garden as well as modeling to understand the ratio of prey/predator for the abovementioned decision making. We suggested that the ratio of prey/predator should be less than 450 for the effective biocontrol of cotton aphid at cotton seedling stage. This finding can improve the efficiency of larger-scale cotton aphid management in China.The decision to delay or cancel spraying insecticides against pest aphids is dependent on the ratio of prey/predator, which reflects how well the predator can suppress the aphid population increase in the field. It is challenging to estimate the ratio of prey/predator due to the multiple factors involved in the interaction between prey and predator. Cotton aphid (Aphis gossypii Glover) is a serious pest, widely distributed in cotton-growing areas around the world. We combined different ratios of aphids with aphid oligophagous ladybird beetles (Coccinella septempunctata Linnaeus) under laboratory and garden conditions to investigate the critical threshold for prey/predator which effectively reduced the cotton aphid population increase. Two kinds of modeling were developed to understand the relationships between the ratio of prey/predator and the PGR (population growth rate), and with the effectiveness of biocontrol (EBC). We found the critical values of PGR should be less than −0.0806 (predators artificially released after 5 days) and then less than −0.075 (predators released after 10 days) if EBC is less than 50%. We recommend that the ratio of prey/predator should be less than 450 for the effective biocontrol of cotton aphids at the cotton seedling stage. These values can be reference indices for the management of aphids in mid-summer.

Do Invasive and Naturalized Aphid Pest Populations Respond Differently to Climatic and Landscape Factors?

Ongoing environmental change affects pest populations, migration, and propensity to damage crops, but the responses to climatic drivers could vary among newly invasive and already naturalized closely related species. To compare these responses of a newly invasive aphid, Metopolophium festucae cerealium (Stroyan), with its naturalized congeneric [M. dirhodum (Walker)] and confamilial [Sitobian avenae (Fab.)], we conducted annual surveys over four years across a total of 141 winter wheat fields in the inland Pacific Northwest, USA. Key climatic factors (cumulative precipitation for each calendar year to sampling date, cumulative degree days), landscape factors (proportion of wheat and landscape diversity within the sample year), and Julian day were calculated for each sampling event, and aphid abundance by species, total aphid abundance, overall species richness, diversity, and aphid community composition were assessed. Metopolophium f. cerealium, the second most abundant species, was positively associated with precipitation, suggesting a projected increase in precipitation in winter and spring in the region could favor its establishment and expansion. Although M. dirhodum and S. avenae linearly (positively) associated with temperature, M. f. cerealium did not, indicating that continued warming may be detrimental to the species. Despite the weak impacts of landscape factors, our study indicated that more wheat generally facilitates cereal aphid abundance. Metopolophium f. cerealium abundance tended to be higher in earlier (May/early June vs. late June/July) samples when wheat crop could be vulnerable to aphid feeding. This study suggests that the new presence of M. f. cerealium has important pest management implications in the region.

Flock house virus as a vehicle for aphid Virus-induced gene silencing and a model for aphid biocontrol approaches

Due to their high specificity and efficacy, RNA interference (RNAi)-based strategies have been used for fundamental functional genomics studies in a number of insects. However, its potential for translational applications in pest management is also of great interest. The lack of suitable RNAi triggering approaches, however, so far has largely precluded the implementation of RNAi-based approaches to target aphids. In this work, we first demonstrate that Flock House virus (FHV), an insect virus, can infect multiple aphid species, including the green peach aphid, Myzus persicae (M. persicae), the corn leaf aphid, Rhopalosiphum maidis (R. maidis), and the bird cherry-oat aphid, Rhopalosiphum padi (R. padi), by both microinjection and oral feeding. Using green fluorescent protein (GFP) as an indicator, we showed that the defective interfering RNA (DI-634) of FHV RNA2, which is generated autonomously during wild-type (WT) virus replication, can carry foreign sequences, and further for their functional expression. More importantly, the engineered DI-634 was incorporated into virus particles in co-infections with WT FHV. Using FHV virions containing genetically modified DI-634, the accumulation levels of the M. persicae mRNAs for Cathepsin L (CatL) and Sugar Transporter 4 (ST4), were decreased by ~ 35% and ~ 30–50%, respectively when virions were injected intrathoracically into aphids. Finally, and of more practical relevance, oral acquisition of these engineered FHV virions caused lethality of M. persicae. In summary, as a proof-of-concept, our work demonstrates that FHV can be a valuable RNAi tool for fundamental research, and suggests opportunities for using engineered insect viruses as biological agents for aphid pest control.

The effect of mature plant resistance in sugar beet (Beta vulgaris spp. vulgaris) on survival, fecundity and behaviour of green peach aphids (Myzus persicae).

Several studies have shown the negative effects of mature plant resistance (MPR) on aphids in sugar beet, which is correlated to the formation of black deposits in their stomach. However, the underlying mechanism of MPR still needs to be elucidated, by understanding the toxicity effects of MPR on aphids and the role of the plant phenological stage and the environment. Here, we report that MPR in sugar beet does not only affect Myzus persicae mortality rate and the formation of a black deposit in the aphid stomach, but also aphid fecundity and behaviour. In addition, experiments in climate-controlled and field settings showed quantitative variation in MPR to M. persicae between six genotypes of sugar beet. Our results indicate that environmental effects, such as temperature, play a major role in MPR and underscore the importance of proper climate-controlled experiments for investigating MPR. In climate-controlled experiments, 83.3% of aphids on old leaves developed a black deposit, in contrast to only 16.8% of aphids on young leaves. This shows that not only plant age, but also leaf age plays a major role in the intensity of MPR. Further research will be needed to identify the underlying mechanism, before MPR can be used as a viable and sustainable solution to aphid pests in sugar beet.

Foliar and Soil Treatments of Brassica napus That Elicit Antibiosis in Brevicoryne brassicae

In screenhouses, foliar and soil applications of induced resistance (IR), nutrient deterrence (ND), and soil amendment (SAM) treatments to canola, Brassica napus L., reduced fitness in an aphid pest, Brevicoryne brassicae L. Effects of different combinations and doses of IR, ND, and SAM on aphids were compared with those of labeled doses of Carbosulfan and a control. Dose differences between treatments and the control were found for several measures of B. brassicae fitness, including Kaplan–Meier functions, reproduction time, effective fecundity (Md), intrinsic rates of natural increase (rm), relative growth rate (RGR), and generation time. Progeny, development/pre-reproductive period, and percent progeny nymph survival were also significantly different from the control. Carbosulfan was the most rapidly acting treatment; however, 1 mM salicylic acid (SA) produced statistically significant reductions in aphid fitness compared to the control, followed by 1 mM citric acid (CA), 0.5 mM SA, and 0.5 mM CA. Silicon (Si) at 50 kg/ha was the most effective ND approach. Ammonium sulfate (AS) only decreased fitness at 25 kg/ha. The SAM combinations of both elemental sulfur (ES) and bio-sulfur (BS) treatments with compost (Cp) also yielded statistically significant aphid fitness reductions. These results provide context for future exploration of IR, ND, and SAM approaches to improve canola yield and reduce aphid damage.

Interactions of predatory coccinellids (Coleoptera: Coccinellidae) and aphids (Hemiptera: Aphididae) in pome and stone fruit orchards of Çanakkale Province

This study revealed the tritrophic interactions of predatory coccinellids-host aphids-host plants on pome and stone fruit trees and herbaceous plants in fruit orchards of Çanakkale Province, Turkey. Field sampling was done during the spring and summer seasons in 2020 and 2021. Twelve predatory species belonging to eight genera from the family Coccinellidae (Coleoptera) were found interacting with eleven host aphids from the family Aphididae (Hemiptera) on eight host plants. A total of 33 tritrophic interactions of predatory coccinellids-host aphids-host plants were revealed on the pome and stone fruit orchards in the Çanakkale Province. From the predators, Harmonia axyridis (Pallas) associated with seven aphids was the most common coccinellid, followed by Oenopia conglobata (L.) which was associated with six aphids. From the aphids, Brachycaudus helichrysi (Kaltenbach) was the most common species; it was associated with ten different predatory coccinellids. Also, from the host plants, the highest number of the interactions of predatory coccinellids-host aphids were revealed on Cydonia oblonga Mill. (Rosaceae) and Prunus domestica L. (Rosaceae) in the pome and stone fruit orchards of Çanakkale Province. As a result, it is considered that the tritrophic interactions of predatory coccinellids-host aphids-host plants should be better understood to increase the success of biological control of pest aphids on the fruit orchards.

Strip intercropping of wheat and oilseed rape enhances biodiversity and biological pest control in a conventionally managed farm scenario

Abstract Conventional agriculture in the global north is typically characterized by large monocultures, commonly managed with high levels of pesticide or fertilizer input and mechanization. Strip intercropping, that is, diversifying cropland by growing strips of different crops using conventional machinery, may be a viable strategy to promote natural predator diversity and associated biological pest control in such conventional farming systems. We tested the influence of strip intercropping of conventionally managed winter wheat with oilseed rape, using common machinery with 27–36 m broad strips, on arthropod predator diversity and biological pest control. We characterized spider and carabid beetle communities, calculated pest aphid and pollen beetle densities and recorded parasitism rates for both crops (number of mummified aphids on wheat and number of parasitized pollen beetle larvae on oilseed rape). We observed a significant reduction in the densities of wheat aphids (50% decrease) and pollen beetle larvae (20% decrease) in strip intercropping areas compared to monocultures. Parasitism rates of wheat aphids increased significantly from 10% in monocultures to 25% in strip intercropping areas. The number of parasitized pollen beetle larvae did not show the same pattern but was higher towards the centre of the oilseed rape strip. Overall, the composition of predator communities benefited from the close neighbourhood of the two crop species in the strips, as carabid beetles were more abundant in oilseed rape and spiders were more abundant in wheat fields. Overall, strip intercropping reduced the dominance of one predator group and allowed for an equal representation of both spiders and carabid beetles in the mixture. Synthesis and applications. Our study presents evidence of the benefits of adopting strip intercropping with relatively large strips (adapted to existing machinery) for natural predator diversity and biological pest control in a large‐scale conventionally managed farm scenario. Wheat–oilseed rape strip intercropping reduced pest densities, increased parasitism of wheat aphids and promoted equal representation of natural predator groups well beyond the areas of monoculture. Overall, by reducing the area dedicated to only one crop, the implementation of strip intercropping adapted to mechanized agricultural scenarios can be used to increase crop heterogeneity at regional scales and enhance biodiversity and biological control, even in simplified landscapes dominated by large‐scale conventional agriculture.

Interactions of aphids (Hemiptera: Aphididae) with their primary and secondary host plants in orchards in Çanakkale Province, Turkey

This study aimed to reveal the interactions of aphids with their primary hosts (pome and stone fruit trees) and secondary hosts (herbaceous plants) in and around orchards in the Çanakkale Province in northwestern Turkey between April-September from 2020 to 2021. Thirty-eight aphid species belonging to 18 genera from two subfamilies, Aphidinae and Calaphidinae, of Aphididae in the order Hemiptera were identified on 53 host plants. Also, 92 aphid-primary-secondary host plant interactions, including several new host plant records for some aphid species in Turkey were revealed in the orchards. Of these hosts, Ballota sp. (Lamiaceae), Carduus pycnocephalus L. (Asteraceae), Conyza sp. (Asteraceae), Diplotaxis sp. (Brassicaceae), Echium plantagineum L. (Boraginaceae), Galium sp. (Rubiaceae), Geranium columbinum L. (Geraniaceae), Papaver rhoeas L. (Papaveraceae), Ranunculus muricatus L. (Ranunculaceae) and Scandix pecten-veneris L. (Apiaceae) are determined as new host plants for some aphids in Turkey. It is believed that the new data on the interactions of aphids with their primary and secondary hosts in orchards will support both a better understanding of the biology of fruit pest aphids and the development of new strategies for the control of aphid pests.

Consumption patterns of the multicolored Asian ladybird Harmonia axyridis on the broad bean aphid Aphis craccivora

• Consumption patterns of ladybirds is meaningful for biological control programs. • Ladybird females were superior predator of aphids base on functional response. • Fourth-instar ladybird larvae suffered from greater intraspecific competition. • Adults and 4th-instar larvae of ladybirds are more effective in controlling aphids. • Intraspecific competition should be considered during field releases of ladybirds. The multicolored Asian ladybird Harmonia axyridis Pallas is often used as a biological control agent against Aphis craccivora Koch, a key pest aphid of broad bean. Understanding consumption characteristics of biological control agents is critical for developing effective biological control programs. Here, under laboratory conditions we studied consumption patterns of H. axyridis on A. craccivora including functional response and intraspecific competition. All larvae (1st-, 2nd-, 3rd-, 4th-instar) and adults (male and female) of H. axyridis exhibited a Type II functional response to A. craccivora . We found H. axyridis females were superior to individuals of other developmental stages, based on three key parameters in functional response model, i.e. attack rate ( a = 90.0%), handling time ( T h = 2.7 min), and consumption threshold ( N max = 526.7 individuals). Results from our analysis of intraspecific competition showed that when attacking A. craccivora , 4th-instar larvae of H. axyridis suffered from the greatest intraspecific competition (coefficient of mutual interference, m = 0.48). Our results show that 4th-instar larvae and adults of H. axyridis are most effective in controlling A. craccivora , and proper density of H. axyridis released will reduce intraspecific competition. This analysis reveals both prey-predator and predator-predator interactions, and highlights the value of biological control in reducing pesticide use and protecting ecological environments.

English

Seed treatment presents an opportunity to boost bean productivity; however, the technology has not been widely tested in Kenya and the sub Saharan Africa region. An experiment was carried out at Kandara, Central Kenya to compare the effects of seed treatment applications on bean performance. The split-plot design experiment with three replicates included four seed treatment products: Apron Star, Seed Plus, Gro Plus and TriCoat applied at recommended and half recommended rates with two bean varieties as test crop. Split-plot ANOVA was implemented using Genstat and agricolae R procedures to compare the effects of seed treatment applications on aphid pest severity and bean performance parameters. Varietal performance differences to the seed treatment were observed with Nyota variety performing better than KATB1. Generally, Apron Star at recommended rates reported lowest pest incidences and consistent bean performance over the two cropping seasons. Consistent treatment effects were observed for recommended rates compared to half rate applications. Under favorable environmental conditions, use of the seed treatment products alone produced yields comparable to the fertilizer treatment. The benefits observed from use of seed treatment technology makes it a potentially sustainable strategy for improving productivity for cash strapped small-scale producers in the region. Key words: Common beans, Kenya, pests, productivity, seed-borne diseases, seed treatment.

Bird predation and landscape context shape arthropod communities on broccoli

Abstract Birds increase crop yields via consumption of pests in some contexts but disrupt pest control via intraguild predation in others. Landscape complexity acts as an inconsistent mediator, sometimes increasing, decreasing, or not impacting pest control. Here, we examined how landscape context and seasonal variation mediate the impact of birds on arthropod pests and natural enemies, leaf damage, and yields of broccoli (Brassica oleracea) on highly diversified farms that spanned the USA west coast. Our study had two complementary components: a bird exclusion experiment and molecular diet analysis of 357 fecal samples collected from the most commonly captured bird species that also foraged in Brassica fields—American Goldfinch (Spinus tristis), American Robin (Turdus migratorius), Savannah Sparrow (Passerculus sandwichensis), Song Sparrow (Melospiza melodia), and White-crowned Sparrow (Zonotrichia leucophrys). Bird access yielded higher, rather than lower, numbers of pest aphids and increased their parasitism, while no other arthropods examined were consistently impacted. Independent of bird presence, percent natural cover in the landscape sometimes increased and sometimes decreased densities of arthropods in the mid-growth period, with diminishing impacts in the late-growth period. Herbivore feeding damage to broccoli leaves decreased with increasing amounts of natural land cover and in the late-growth period. Molecular diet analysis revealed that Brassica pests and predatory arthropods were relatively uncommon prey for birds. Landscape context did not alter the prey items found in bird diets. Altogether, our bird-exclusion experiment and molecular diet analysis suggested that birds have relatively modest impacts on the arthropods associated with broccoli plantings. More broadly, the limited support in our study for net natural pest control services suggests that financial incentives may be required to encourage the adoption of bird-friendly farming practices in certain cropping systems.

The phylogenetic and evolutionary analyses of detoxification gene families in Aphidinae species.

Detoxification enzymes play significant roles in the interactions between insects and host plants, wherein detoxification-related genes make great contributions. As herbivorous pests, aphids reproduce rapidly due to parthenogenesis. They are good biological materials for studying the mechanisms that allow insect adaptation to host plants. Insect detoxification gene families are associated with insect adaptation to host plants. The Aphidinae is the largest subfamily in the Aphididae with at least 2483 species in 256 genera in 2 tribes: the Macrosiphini (with 3/4 of the species) and the Aphidini. Most aphid pests on crops and ornamental plants are Aphidinae. Members of the Aphidinae occur in nearly every region of the world. The body shape and colour vary significantly. To research the role that detoxification gene families played in the process of aphid adaptation to host evolution, we analyzed the phylogeny and evolution of these detoxification gene families in Aphidinae. In general, the P450/GST/CCE gene families contract, whereas the ABC/UGT families are conserved in Aphidinae species compared to these families in other herbivorous insects. Genus-specific expansions of P450 CYP4, and GST Delta have occurred in the genus Acyrthosiphon. In addition, the evolutionary rates of five detoxification gene families in the evolution process of Aphidinae are different. The comparison of five detoxification gene families among nine Aphidinae species and the estimated relative evolutionary rates provided herein support an understanding of the interaction between and the co-evolution of Aphidinae and plants.

Multi-scale approach to biodiversity proxies of biological control service in European farmlands

Intensive agriculture has profoundly altered biodiversity and trophic relationships in agricultural landscapes, leading to the deterioration of many ecosystem services such as pollination or biological control. Information on which spatio-temporal factors are simultaneously affecting crop pests and their natural enemies is required to improve conservation biological control practices. We conducted a study in 80 winter wheat crop fields distributed in three regions of North-western Europe (Brittany, Hauts-de-France and Wallonia), along intra-regional gradients of landscape complexity. Five taxa of major crop pests (aphids and slugs) and natural enemies (spiders, carabids, and parasitoids) were sampled three times a year, for two consecutive years. We analysed the influence of regional (meteorology), landscape (structure in both the years n and n-1) and local factors (hedge or grass strip field boundaries, and distance to boundary) on the abundance and species richness of crop-dwelling organisms, as proxies of the service/disservice they provide. Firstly, there was higher biocontrol potential in areas with mild winter climatic conditions. Secondly, natural enemy communities were less diverse and had lower abundances in landscapes with high crop and wooded continuities (sum of interconnected crop or wood surfaces), contrary to slugs and aphids. Finally, field boundaries with grass strips were more favourable to spiders and carabids than boundaries formed by hedges, while the opposite was found for crop pests, with the latter being less abundant towards the centre of the fields. We also revealed temporal modulation—and sometimes reversion—of the impact of local elements on crop biodiversity. To some extent, these results cause controversy because they show that hedgerows and woodlots should not be the unique cornerstones of agro-ecological landscape design strategies. We point out that combining woody and grassy habitats to take full advantage of the features and ecosystem services they both provide (biological pest control, windbreak effect, soil stabilization) may promote sustainable agricultural ecosystems. It may be possible to both reduce pest pressure and promote natural enemies by accounting for taxa-specific antagonistic responses to multi-scale environmental characteristics.