Reduced Aphid Populations Research Articles

Effect of Plant Identity in Wheat Mixtures on English Grain Aphid (Sitobion avenae) Control

ABSTRACTField experiments have demonstrated that wheat mixtures differ in their ability to regulate aphid populations. To further investigate the effectiveness of wheat mixtures (Triticum aestivum and Triticum turgidum) in controlling aphids, we conducted both laboratory and greenhouse experiments. Specifically, we assessed the associational resistance of two wheat mixtures (Florence‐Aurora with Forment, Florence‐Aurora with Montcada), and their respective monocultures, in different stages of the aphid host selection process. We analysed aphid acceptance rate, population growth, and load under different wheat treatments. Additionally, we characterised wheat aboveground biomass and nitrogen content as important functional traits for aphid resistant. Aphid acceptance decreased in plants of cv. Forment when exposed to volatiles from undamaged Florence‐Aurora plants, whereas the other tested combinations tested had no effect. Aphids performed differently in the two mixtures: Florence‐Aurora mixed with Forment significantly reduced aphid population growth and load compared to the monocultures, whereas the combination of Florence‐Aurora with Montcada wheat had no effect on aphid performance. The plant–plant interactions also modified the analysed traits. Nitrogen content of Florence‐Aurora wheat plants was reduced when mixed with Forment wheat, which may explain the lower aphid load observed in plants of cv. Florence‐Aurora when mixed with plants of cv. Forment. However, mixing wheats with similar aboveground biomass resulted in an increase in the average biomass of plants of both cultivars which could have led to a higher aphid population. The data supports the idea of right neighbour, as the benefits of wheat mixtures for aphid control were determined by the identity of the combined plants (or species). Finally, our results suggest that associating wheats with different traits may promote facilitative interactions, which in turn enhances associational resistance, whereas the combination of wheats with similar traits may result in competitive interactions that may hinder aphid control benefits.

Strip‐cropping legacy enhances potato plant defence responses to aphids via soil‐mediated mechanisms

Abstract Intensive agriculture often comes at the expense of soil health. A shift towards practices that foster soil health will support yield and defences against pests and diseases. Growing crops in monoculture is the standard in modern agriculture, though strip‐cropping, in which different crops are planted in strips, is a promising strategy in the transition towards sustainable agriculture. Increasing crop diversity is hypothesized to positively influence arbuscular mycorrhizal fungi (AMF), thereby enhancing soil health, but the mechanisms by which AMF‐plant symbioses contribute to higher yields and reduced pest populations in strip‐cropping systems remain unclear. We used a green‐house experiment with potato plants to explore the soil legacy effects of mono‐cropping versus strip‐cropping systems, AMF inoculation and aphid infestation on AMF root colonization, the induction of plant defences (untargeted LCMS‐based metabolomics), aphid population size and potato yield. We found that potato plants grown in strip‐cropping soil had higher AMF colonization than plants grown in mono‐cropping soil. Potato plants grown in strip‐cropping soil also had higher shoot nitrogen content, increased solamargine levels, and reduced aphid populations. AMF root colonization was only enhanced by the addition of commercial AMF in mono‐cropping soils. Potato plant metabolites were affected by strip‐cropping soil, including jasmonic acid (JA) derivatives. Structural equation models revealed that strip‐cropping soil directly reduced aphid populations and also had a negative direct effect on the JA precursor OPC‐8, and hydroxyJA‐glucosides, indicating complex effects of strip‐cropping soils on JA‐inducible plant defences. Indirect benefits of strip‐cropping soil and AMF inoculation on tuber yield were mediated by their direct positive effects on plant nitrogen content. Our results emphasize the potential of strip‐cropping to enhance AMF root colonization in the field. We show that soil legacy effects of strip‐cropping alter the plant metabolome in ways that suppress of aphid populations. Strip‐cropping legacy effects are the result of crop diversity, crop neighbour and edge effects resulting from crop management practices. While the mechanisms by which soil from strip‐cropping supresses pest populations still need to be identified, our study underscores the potential for strip‐cropping to enhance pest control and yield via soil mediated processes. Read the free Plain Language Summary for this article on the Journal blog.

Conventional Versus Biorational Insecticides for Controlling Mustard Aphid and Their Effects on Beneficial Insects

Mustard is one of the most important oilseed crops in Bangladesh. However, its production is severely constrained by aphid infestation. Farmers usually spray conventional insecticides to control aphids that negatively affect beneficial insects and environment. Thus, alternatives to conventional insecticides are required. We tested three biorational insecticides (Nimbicidine @ 1ml/L, Spinosad: Libsen 45SC @ 0.5 ml/L and Lufenuron: Hayron 5EC @ 0.5ml/L of water) against aphid infestation and assessed their effect on ladybird beetle and honey bee and compared these effects with two conventional insecticides (Diazinon: Sabion 60EC @ 2ml/L and Cypermethrin: Cypraplus 10EC @ 1ml/L of water) and with an untreated control. The study was conducted in a randomized complete block design with each treatment replicated thrice in the field of Department of Entomology, Bangladesh Agricultural University. Number of infested plants per plot, aphid per plant and per pod, number of ladybird beetle and honey bee per plot was counted and yield per plot was calculated. All tested insecticides reduced aphid infestation compared to untreated control indicating all of them were effective against aphid. However, Lufenuron and Nimbicidine was most effective to reduce plant infestation and number of aphids per plant and pod. Spinosad and Sabion were found fairly effective whereas Cypraplus was found to be least effective. Lufenuron and Nimbicidine did not reduce the number of ladybird beetle and honey bee visit per plot, however, Spinosad and conventional insecticides reduced their number. Lufenuron treated plots provided highest yield (1.35 t/ha) followed by Nimbicidine (1.15 t/ha), Spinosad (1.10 t/ha) and Sabion (1.00 t/ha) whereas Cypraplus treated plots provided lowest yield (0.9 t/ha). In terms of reducing aphid population thus plant infestation and increasing yield, all biorational insecticides performed better than conventional insecticides, however, concerning effect on ladybirds and honey bees, only Lufenuron and Nimbicidine can be recommended to farmers. J Bangladesh Agril Univ 22(3): 335-341, 2024

Geographic variation in evolutionary rescue under climate change in a crop pest-predator system.

Species distribution models (SDMs) are often built upon the "niche conservatism" assumption, such that they ignore the possibility of "evolutionary rescue" and may underestimate species' future range limits under climate change. We select aphids and ladybirds as model species and develop an eco-evolutionary model to explore evolutionary rescue in a predator-prey system under climate change. We model the adaptive change of species' thermal performances, accounting for biotic interactions. Our study suggests that, without considering evolutionary adaptation, the warming climate will result in a reduction in aphid populations and the extinction of ladybirds in large parts of the United States. However, when incorporating evolutionary adaptation into the model, aphids can adapt to climate change, whereas ladybirds demonstrate geographic variation in their evolutionary rescue potential. Specifically, ladybirds in southern regions are more likely to be rescued than those in the north. In certain northern regions, ladybirds do not avoid extinction due to severe warming trends and seasonality of the climate. While higher warming trends do prompt stronger evolutionary changes in phenotype, they also lead to reduced aphid population abundance such that ecology constrains ladybird population growth. Higher seasonality induces an ecological effect by limiting the length of reproductive season, thereby reducing the capacity for evolutionary rescue. Together, these findings reveal the complex interplay between ecological and evolutionary dynamics in the context of evolutionary adaptation to climate change.

Efficacy of Plant Extracts for the Control of Pepper Insect Pest (Green Peach Aphid (Myzus persicae L.)

Aphids pose significant threats to crop productivity, necessitating effective and sustainable pest management strategies. This study investigated the repellent properties of neem and papaya leaf extracts on green peach aphids and the impact of the extracts on plant growth in pepper (Capsicum spp.). The experiment involved 7 treatments and 3 treatment replications with varying concentrations of neem and papaya extracts (6.5 v:v, 7.5 v:v, and 8.5 v:v) compared to a control group (Distilled water). The Randomized Complete Block Design (RCBD) was used as an experimental design. The study site was Cuttington University’s College of Agriculture Research site. The distances between plots and blocks were 0.6 m and 1 m, correspondingly. In the laboratory bioassay, results uncovered distinct trends, with the control treatment exhibiting the highest mean aphid count (41.0), while neem 8.5 v:v (6.0) and papaya 8.5 v:v (8.1) treatments established substantial effectiveness in reducing aphid populations. The highest mean aphid counts following biopesticidal application were 48.0 and 76.7 after 1 and 2 weeks, respectively and were recorded in the untreated control plots, while the lowest mean aphid counts were 21.3 and 6.0 after 1 and 2 weeks, respectively. Furthermore, neem 8.5 v:v treatment consistently showed the highest mean values across plant height (16.2 cm), leaf length (8.2 cm), leaf width (5.2 cm), and repellency index (3.0), indicating potential positive impacts on plant growth and repellency. Untreated control measured the lowest values for plant height (13.8 cm), leaf length (6.0 cm) and repellency index (1.0). The study demonstrated the potential of both extracts to suppress aphid populations and enhance plant growth. Applying these natural extracts as part of an integrated pest management (IPM) strategy can be beneficial for controlling aphid infestations in pepper crops. Their use as repellents can reduce aphid populations, minimizing potential crop damage and yield losses.

Evaluation of lethal and sublethal effects of laminarin on the green peach aphid,Myzus persicae, under extended laboratory conditions

AbstractRecent studies have opened the way for using elicitor‐induced resistance in plants as a method to control arthropod pests. In this study, 1,3‐β‐glucan laminarin, an elicitor of disease resistance in plants, was tested on the green peach aphid,Myzus persicae(Sulzer) (Hemiptera: Aphididae), on peach [Prunus persica(L.) Batsch, Rosaceae] plantlets and evaluated its effects on short‐term mortality and population growth. Laminarin exposure did not affect aphid survival in the short term; however, laminarin‐treated peach plants sustained fewer nymphs and adults in comparison with the control. Aphid populations on plants treated with laminarin declined significantly over the sampling period compared to the control. Moreover, the demographic parameters net reproductive rate (R0), finite rate of increase (λ), and intrinsic rate of increase (rm), all showed decreasing trends in aphid populations reared on laminarin‐treated plants. The decline in aphid populations exposed to laminarin seemed to mainly be linked to reduced adult survival, slower nymph development, and lower nymph survival and only marginally to changes in reproduction outcome. Changes in gene expression causing the final production of defence chemicals by peach plants may contribute to explaining the results. However, potential direct effects of laminarin onM. persicaefeeding activity and probing behaviour cannot be ruled out. This study provides evidence that, although laminarin did not display insecticidal activity in the short term, this elicitor caused sublethal effects, significantly reducing aphid populations.

Trophic impacts of a rolled‐rye cover crop on the lettuce aphid (Nasonovia ribisnigri) and associated insect fauna in cultivated Histosols

AbstractCultivated peatland (Histosol) in Southern Québec (Canada) is a rapidly declining non‐renewable resource used to grow most Canadian lettuce (Lactuca sativa L., Asteraceae). Rolled‐rye (Secale cereale L., Poaceae) cover crop is one of the conservation practices proposed to reach a more sustainable lettuce production, but the overall impact on the agroecosystem remains poorly studied in Histosols. We assessed multiple effects of rolled‐rye cover crop on the trophic chain associated with the lettuce aphid, Nasonovia ribisnigri (Mosley) (Hemiptera: Aphididae), a major pest of lettuce. During one growing season and through two consecutive lettuce crops, we monitored in situ the impacts of rolled‐rye cover crop on insect fauna and lettuce quality. We used visual scouting and yellow pan traps to assess plant colonization by N. ribisnigri, its natural enemies, and alternative prey. Exclusion cage experiments were also conducted to measure aphid fitness and population growth. Under greenhouse conditions, following cover crop removal, we examined potential lingering effects of rye within the soil on lettuce plants and N. ribisnigri. In situ experiments showed that rolled‐rye cover crop has the potential to inhibit N. ribisnigri field colonization and recruit natural enemies and alternative prey in the first lettuce crop. Rye also reduced aphid fitness as well as lettuce foliar amino acid concentration and weight. For the second lettuce crop, an almost 50% reduction in N. ribisnigri abundance was observed with the use of rolled‐rye cover crop. In greenhouse experiments, no persistent effect of rye was observed on the quality of lettuce grown with soil collected under a cover crop, nor on the fitness of aphids inoculated on these lettuces. This study highlights the diversity of trophic effects rolled‐rye cover crop may have on lettuce production in Histosols and the potential of rolled‐rye cover crop as a cultural practice to reduce aphid populations. Mechanisms at play while underlining agronomic challenges regarding proper rye termination must be further explored to maintain high‐performing lettuce yields.

Functional Response and Intraspecific Competition of Three Ladybird Species Feeding on Aphids on Goji Berry Plants in Laboratory and Semi-Field Conditions.

The aphid, Aphis gossypii Glover, is identified as a significant pest that causes severe damage to goji berries in China. To analyze the ladybird consumption of aphids, the functional responses of three ladybird species, Harmonia axyridis, Coccinella septempunctata, and Hippodamia variegata, and intraspecific competition among ladybird individuals were evaluated under laboratory conditions. Moreover, the practical impact of ladybirds on aphid population reduction was investigated in semi-field conditions. We found that all adult ladybirds of the three species exhibited a type II functional response toward aphids. According to Holling's disc equation, H. axyridis exhibited the highest searching efficiency (a = 0.79), while C. septempunctata had the shortest handling time (Th = 5.07 min) among the three ladybird species studied. Additionally, intraspecific competition had a greater impact on H. variegata (m = 0.41) compared to the other two ladybird species. The semi-field study demonstrated that H. axyridis (83.9% reduction) and C. septempunctata (78.7% reduction) exhibited higher efficacy in reducing aphid populations compared to H. variegata (27.3% reduction). This study suggests that H. axyridis and C. septempunctata exhibit potential as effective biological control agents against aphids on goji berry plants and highlights the importance of considering intraspecific competition. However, the results obtained from laboratory and semi-field studies cannot be directly extrapolated to field conditions due to the simplification of these experimental systems. Future field studies are crucial in ensuring the effective implementation of a biological control program.

Jasmonic acid impact on botanical and morpho-physiological characteristics of wheat (Triticum aestivum L.) infected by Aphid

Wheat (Triticum aestivum L.) is the most essential cereal crop among all other crops of Pakistan and belongs to the family poaceae. The experiment was performed to evaluate the response of exogenously applied jasmonic acid on wheat (Triticum aestivum L.) growth parameter against aphid attack. Two wheat varieties i.e., Fareed-2006 and Paktoon-2016 are cultivated in pots and different concentrations of Jasmonic acid (100 µM and 1 mM) were applied. Concluded results showed that aphid infested plants decreased root and shoot length, plant height, total soluble protein and chlorophyll contents but increased the POD and SOD contents, MDA contents, catalase, H2O2 concentrations and phenolics of wheat (Triticum aestivum) which was further improved through jasmonic acid application. Jasmonic acid treated plants showed better results than control and aphid infested plants. Jasmonic acid spray helped plants to recovery from aphid stress by increasing antioxidant enzyme synthesis, POD (Peroxidase), SOD (Superoxide dismutase) and CAT (Catalase). The results showed that JA sprayed plants have a reduced aphid population than controls plants. When compared to jasmonic acid (100 µM), the greater concentration of jasmonic acid (1mM) showed more effective. Use of jasmonic acid against devastating diseases seems to hold a more promising future in the pest management and agriculture sector.

Aphidophagous predators in commercial Capsicum cultivars and characterization of their trophic network using stomach content analysis

AbstractViruses and aphids, the most recent vectors of viruses (Hemiptera: Aphididae) of the genera Myzus and Aphis, are the main phytosanitary problems of Capsicum spp. (Solanales: Solanaceae) agricultural systems in Colombia. The incorporation of biological control in integrated pest management (IPM) programmes, which can be used to reduce aphid populations in solanaceous crops, is hampered by the lack of information on the natural enemy community, such as parasitoids, predators and generalist aphidophagous. For this reason, the objective of this research was to determine and characterize the community of generalist aphidophagous (Coccinellidae and Syrphidae) in the cultivation of chilli pepper in south‐western Colombia, and to characterize their diet through stomach content analysis using next‐generation sequencing (NGS) techniques. Two species of Coccinellidae and one species of Syrphidae were the most abundant predators in commercial crops of Capsicum spp. and fed preferentially on aphids that attacked the pepper plants. The characterization of the diet of these predators using molecular tools revealed intraspecific predation, secondary predation of aphid parasitoids and consumption of alternative prey to the aphids attacking the pepper plants. Differences in diet composition were observed between larval and adult coccinellids, and between coccinellids and the hoverfly species studied. The results suggest that dominant predators may be suitable for use in IPM programmes to control aphids in pepper crops, as their diet consists mainly of aphids that attack pepper plants. In addition, these predators can take advantage of the agricultural matrix by feeding on alternative prey in the absence of aphids.

Volatile interactions between specific undamaged barley cultivars affect aphid feeding behavior and performance

Recent studies have demonstrated that cultivar mixtures can reduce aphid plant acceptance and population development. It is still unknown as to which underlying mechanisms may contribute to this phenomenon. We investigated the effects of volatile interactions between undamaged barley cultivars on aphid feeding behavior and performance in the laboratory. Spring barley (Hordeum vulgare L.) cultivar Salome was exposed to volatiles from Fairytale (SeF), Anakin (SeA), or clean air (Se0). We used an electrical penetration graph to test the effect of exposure to neighbor volatiles on the feeding behavior and performance of bird cherry-oat aphids (Rhopalosiphum padi L.). We also assessed aphid relative growth rate, intrinsic rate of increase, and development time on exposed and unexposed Salome plants. Aphids spent significantly longer time on epidermis and mesophyll plant tissues on SeF than Se0, and no difference was observed between SeA and Se0. Significant decreases in the duration of phloem ingestion and phloem sustained ingestion were recorded in SeF showing that volatile-induced effects cause difficulty for aphids to feed. However, no differences in these variables were detected between SeA and Se0. We also observed reduced aphid relative growth rate and intrinsic rate of increase on SeF compared to Se0 and SeA. Our study demonstrated that, in a specific combination, exposure of one barley cultivar to volatiles from another one can change aphid feeding behavior and performance, probably due to changes in host plant properties/quality. Our results provide an insightful explanation of mechanisms responsible for the reduced aphid population development previously observed in the field.

Management of powdery mildew and aphid in organically grown Indian mustard (Brassica juncea L.) through different oils

All the cultivated Brassica species exhibited powdery mildew severity with highest (43.2%) on Brassica juncea followed by B. rapa (28.0%) which is widely cultivated in India. Yield losses from 10-90 per cent with reduction in 6.47 per cent oil content have been estimated from different Brassica species. Hence, the present study was carried out to evaluate different oils to manage powdery mildew disease and aphids in an organically grown mustard crop. Five oils (castor, groundnut, sunflower, neem and mustard oil) and ghee were evaluated against powdery mildew (Erysiphae cruciferarum) and aphid (Lipaphis erysimi) of Indian mustard (Brassica juncea). Castor oil 50 EC, neem oil 50 EC and mustard oil 50 EC and deshi ghee 50 EC (@ 100 ml/10 litre water) were effective over untreated control in reducing powdery mildew disease severity when applied as foliar spray (@ 5 ml/litre) in the experiment carried out in organic field (plot No. B-2 at Agronomy Instruction Farm, S. D. Agricultural University, Sardarkrushinagar). Maximum reduction in germinated conidia (66.0%) over control, disease severity (50.0%), area under disease progress curve (AUDPC) values (51.8%) and maximum increase over control in 1000 seed weight (16.7%) and seed yield (10.3%) was observed with neem oil. This was followed by the application of ghee which exhibited reduced disease severity (22.9%) and AUDPC values (30.6%) and increased seed yield (8.1%) and the application of castor oil 50 EC which exhibited an increased in seed yield (8.0%) and reduced powdery mildew severity (20.8%). Shortest log phase was observed with neem oil during 10th std. week. All the oils tested (castor, groundnut, sunflower, neem and mustard oil) and deshi ghee were effective in reducing aphid population (39.5 to 65.9%) and damage index (6.1 to 25.1%). A maximum reduction in aphid population (65.9%) over control and lowest aphid damage index (3.70) was observed with neem oil 50 EC 6 days after 2nd spray. Application of neem oil, castor oil and deshi ghee resulted in increased seed yield (8.1 to 10.4%). This information could be useful in devising strategies for powdery mildew and aphid management in organic cultivation, eco-friendly management and IPM of mustard.

Providing sugar sources for ants improves the biological control of Aphis spp. in apple orchards

The green apple aphids Aphis pomi DeGeer and A. spiraecola Patch are serious pests of apple, especially in young orchards, where both species establish facultative mutualisms with ants. This study, conducted in Hungary in 2014 and 2015, manipulated the presence of the common black ant Lasius niger (L.) on colonies of Aphis spp. in apple tree canopies. To this end, two kinds of sugar dispensers (bottle dispensers and agar jelly cubes), each providing a sucrose solution with 300 g/1000 ml concentration, were deployed as alternative sugar sources for the ants, with plots lacking dispensers serving as controls. Both forms of sugar provisioning reduced the number of ants tending Aphis spp. colonies and reduced aphid populations compared to controls in both years. However, bottle dispensers demonstrated consistent efficacy in both years, whereas agar jelly cubes were less reliable in distracting the ants. Both treatments significantly increased the abundance of natural enemies at Aphis spp. colonies compared to controls. Our results indicate that the provisioning of ants with sugar in apple orchards can effectively disrupt ant-aphid mutualisms in the case of Aphis spp., by drawing ants away from aphid colonies and thus increasing natural enemy predation on aphid colonies. The use of sugar-feeding tactics to alter ant behaviour should permit reduced pesticide use in apple orchards, whether to control aphids or other pests that might serve as prey for ants, and is fundamentally compatible with biological pest control in apple orchards.

Dual purpose: Predatory hoverflies pollinate strawberry crops and protect them against the strawberry aphid, Chaetospihon fragaefolii.

Predatory syrphids are an important functional group due to their potential for providing multiple ecosystem services. Adults feed on nectar and pollen, and can be effective pollinators, while larvae are voracious predators that can reduce aphid pressure. Still, little research has addressed their potential dual function in agroecosystems. In this study, we assessed the potential of two predatory hoverflies, Eupeodes corollae and Sphaerophoria rueppellii, for delivering concurrent pollination and biological control of Chaetospihon fragaefolii in greenhouse strawberries. Both hoverfly species effectively pollinated strawberry flowers of two different varieties ('Elsanta' and 'Sonsation'), resulting in an increase in high-quality marketable fruits, a reduction of fruit deformities, and higher number of seeds per fruit compared to pollinator-excluded fruits. S. ruepellii had a significantly longer flower handling time than E. corollae, which translated to a more efficient pollination expressed as higher seed numbers per fruit after a single flower visit. By contrast, flowers that were open to multiple visits were more effectively pollinated by E. corollae, suggesting that E. corollae is potentially a better cross-pollinator than S. rueppellii. In addition, both hoverfly species suppressed aphid populations in strawberry (var. 'Sonata'), with S. rueppellii and E. corollae reducing aphid populations by 49% and 62%, respectively. Predatory syrphids can concurrently contribute to pollination and biological control in strawberry in a greenhouse setting. © 2022 Society of Chemical Industry.

Effect of flower identity and diversity on reducing aphid populations via natural enemy communities.

Floral plantings are often used in agriculture to attract pollinator communities, but they also play an important role in recruiting and establishing natural communities for natural pest control. Inconsistent effects of floral plantings for pest control may be a result of an absence of mechanistic insights and a reliance on the idea that simply increasing flower diversity will benefit these services. A more tailored set of flower species may be needed to benefit the natural enemies through provision of nectar and alternative prey. We used an outside pot experiment to investigate the effect of three flower plants (Fagopyrum esculentum, Vicia faba, and Trifolium pratense) on reducing aphid pests on four different plant cultivars of barley (Hordeum vulgare), over two years. We grew the four cultivars of barley alone, next to a single flower or next to a mixture of flowers, and observed aphid and natural enemy colonization across the growing season. Aphid population sizes were reduced on all barley cultivars grown next to a flower with stronger pest suppression when all flowers were present. Each flower species recruited a different community of non‐barley aphids that, in turn, varied in their ability to establish the natural enemy populations and subsequently the ability to reduce barley aphid populations. Overall, increased pest suppression in the mixed treatments was a result of numerous weaker interactions between different flower, aphid, and natural enemy species, rather than a few dominant interactions. Natural enemy communities could be enhanced by incorporating flower species that vary in their ability to attract and host alternative prey (i.e., non‐pest aphids) as well as suitable nectar provisioning. We can use our knowledge of ecological interactions to tailor floral plantings to increase the effectiveness of pest control services.

Identifying aphid resistance in the ancestral wheat Triticum monococcum under field conditions

Wheat is an economically, socially, and nutritionally important crop, however, aphid infestation can often reduce wheat yield through feeding and virus transmission. Through field phenotyping, we investigated aphid resistance in ancestral wheat Triticum monococcum (L.). Aphid (Rhopalosiphum padi (L.), Sitobion avenae (F.) and Metopolophium dirhodum (Wlk.)) populations and natural enemy presence (parasitised mummified aphids, ladybird adults and larvae and lacewing eggs and larvae) on two naturally susceptible wheat varieties, Triticum aestivum (L.) var. Solstice and T. monococcum MDR037, and three potentially resistant genotypes T. monococcum MDR657, MDR045 and MDR049 were monitored across three years of field trials. Triticum monococcum MDR045 and MDR049 had smaller aphid populations, whereas MDR657 showed no resistance. Overall, natural enemy presence was positively correlated with aphid populations; however, MDR049 had similar natural enemy presence to MDR037 which is susceptible to aphid infestation. It is hypothesised that alongside reducing aphid population growth, MDR049 also confers indirect resistance by attracting natural enemies. The observed resistance to aphids in MDR045 and MDR049 has strong potential for introgression into commercial wheat varieties, which could have an important role in Integrated Pest Management strategies to reduce aphid populations and virus transmission.

Efficacy of plant derived and synthetic insecticides against cabbage aphid, Brevicoryne brassicae (L.) (Homoptera: Aphididae) and their effect on coccinellid predators

Cabbage aphid, Brevicoryne brassicae (L.) is one of the major insect pests of brassica crops worldwide. Mainly insecticides are being used for its management which poses hazardous effects on the environment and the applicator. Low efficacy and non-target effect of the available insecticide are the main challenge in the management of the pest in Ethiopia. The use of bio-rational and neonicotinoid pesticides is a promising alternative as they are less vulnerable to resistance development and relatively safe to the environment and the applicator. This study was carried out in 2018/19 cropping season to evaluate the efficacy of plant derived and synthetic insecticides for the management of cabbage aphid and their effect on coccinellid predators on Ethiopian kale. Ten treatments including six synthetic and two botanical insecticides were tested in comparison with the standard check dimethoate 40% EC and the untreated control in Randomized Complete Block Design with three replications. Significant (P<0.05) differences were observed among the treatments in terms of cabbage aphid population reduction and their effect on coccinellid beetles. The botanical mix (Garlic+onion+pepper) and imidacloprid were at par with each other and found to be the best treatment with 93.79% and 91.04% efficacy, respectively. The maximum leaf yield was obtained from imidacloprid (14.18 t/ha) followed by botanical mix (13.45 t/ha) and lufenuron (12.42 t/ha). The highest yield increment over control was obtained from imidacloprid (3.1 t/ha), followed by botanical mix (2.37 t/ha). The botanical mix, imidacloprid and neem seed extract were highly effective in aphid control as well as less hazardous to ladybird beetle (Coccinella septempunctata L.). The highest cost benefit ratio was recorded with profenofos (1:1.14) followed by lufenuron (1:0.2), spinosad and nimbecidine (1:0.18). Results of the current study demonstrated that imidacloprid and plant-based insecticides can reduce aphid populations equally to conventional insecticides and could be used as an alternative component for the integrated pest management (IPM) of cabbage aphid, Brevicoryne brassicae (L.) on kale crop under field condition of smallholder farming system.

Seed inoculations with entomopathogenic fungi affect aphid populations coinciding with modulation of plant secondary metabolite profiles across plant families.

Entomopathogenic fungi (EPF) can display a plant-associated lifestyle as endophytes. Seed application of EPF can affect insect herbivory above ground, but the mechanisms behind this are not documented. Here we applied three EPF isolates, Beauveria bassiana, Metarhizium brunneum and M.robertsii, as seed inoculation of wheat and bean, and evaluated the effects on population growth of aphids, Rhopalosiphum padi and Aphis fabae, respectively. In wheat and bean leaves, we quantified benzoxazinoids and flavonoids, respectively, in response to EPF inoculation and aphid infestation to elucidate the role of specific plant secondary metabolites (PSMs) in plant-fungus-herbivore interactions. Inoculations of wheat and bean with M.robertsii and B.bassiana reduced aphid populations compared with control treatments, whereas M.brunneum unexpectedly increased the populations of both aphids. Concentrations of the majority of PSMs were differentially altered in EPF-treated plants infested with aphids. Changes in aphid numbers were associated with PSMs regulation rather than EPF endophytic colonisation capacity. This study links the effects of EPF seed inoculations against aphids with unique PSM accumulation patterns in planta. The understanding of PSM regulation in tri-trophic interactions is important for the future development of EPF for pest management.

Parasitization of the sugarcane aphid, Melanaphis sacchari, by commercially available aphid parasitoids

Identification of natural enemies of novel pests is important for the development of effective integrated pest management. Commercially available parasitoids used for control of arthropod pests have potential for enhancing biological control of invasive pests. The sugarcane aphid, Melanaphis sacchari (Hemiptera: Aphididae), is a new pest on sweet sorghum, Sorghum bicolor, in the USA. Surveys of M. sacchari have not detected any parasitoids in central Kentucky. In North America, Aphelinus abdominalis (Hymenoptera: Aphelinidae), Aphidius ervi (Hymenoptera: Braconidae), Aphidius colemani, and Aphidius matricariae are sold for aphid management. This study’s objective was to determine the host acceptance and suitability of M. sacchari for these parasitoid species. Host acceptance was assessed by counting attacks and oviposition strikes by parasitoids on M. sacchari. All parasitoid species accepted M. sacchari as a host in the parental generation (purchased adults) and the F1 generation (reared from M. sacchari). Host suitability was evaluated by transferring M. sacchari from host acceptance trials to caged sweet sorghum plants. Cages were monitored for aphid mummies and emerged adult parasitoids. Parental A. colemani produced the most mummies and adult parasitoids and reduced final M. sacchari numbers by 75%. A. ervi had a similar impact on M. sacchari populations but produced fewer mummies and adults. A. matricariae and A. abdominalis did not reduce M. sacchari populations. F1 parasitoids produced few adults and did not reduce M. sacchari populations. A. colemani demonstrated potential for field releases with the ability to use M. sacchari as a host and reduce aphid population growth.

Dual ecosystem services of syrphid flies (Diptera: Syrphidae): pollinators and biological control agents

With increasing worldwide pressure on bee pollinator populations and an increase in insecticide resistance amongst pest insects, there is a growing need for diversification of pollinator and pest control systems. Syrphid flies (Diptera: Syrphidae) contribute ecosystem services to agroecosystems through their supporting roles as crop pollinators and predators of pests. Adult syrphids are important pollinators with high floral visitation rates and pollen carrying capacity, while predatory syrphid larvae are natural biological control agents, reducing aphid populations in both field and laboratory conditions. The present challenge is to determine whether syrphid flies have the potential for application as pollinators and in integrated pest management (IPM) schemes as biological control agents. Currently, there are gaps in research that are hindering the use of syrphids as dual service providers. Such gaps include a lack of knowledge of syrphid floral preferences, the role and viability of adult syrphids as pollinators in natural and agro-ecological pollinator networks, and the predatory efficiency of larvae in field and greenhouse conditions. By reviewing relevant literature, we demonstrate syrphids flies have the potential to be used as pollinators and biological control agents. This article is protected by copyright. All rights reserved.