Reduced Aphid Populations Research Articles

Evaluation of Scymnus nubilus (Coleoptera: Coccinellidae) as a biological control agent against Aphis spiraecola and Cinara juniperi (Hemiptera: Aphididae)

Aphids are a major insect pest of forestry systems. In this study, we evaluate the potential of the ladybeetle Scymnus nubilus Mulsant (Coleoptera: Coccinellidae) as a biological control agent against Aphis spiraecola Patch and Cinara juniperi (De Geer) (Hemiptera: Aphididae) infesting Azorean endemic plants reared in forestry nurseries. Aphis spiraecola, infesting Viburnum treleasei Gand. (Dipsacales: Adroxaceae), was the most abundant aphid; however, a higher proportion of Juniperus brevifolia (Seub.) Antoine (Pinales: Cupressaceae) was infested by C. juniperi. Scymnus nubilus fourth instar larvae were able to complete development on both aphid species. Voracity was significantly higher when S. nubilus was fed on A. spiraecola but biomass consumption was significantly lower. The relative growth rate and conversion efficiency of the fourth instar larvae were similar. Field experiments indicated that S. nubilus can contribute to the decrease in pest population densities. However, the fourth instar larvae proved to be more efficient when released onto A. spiraecola; this outcome can be attributed to the distribution patterns of the aphids on the host plant and to the aphid or host plant morphology. Predator density and sleeve cage effect are apparently critical factors in reaching an efficient control. The obtained results provide the essential preliminary information required to establish future programs of biological control against aphids infesting Azorean endemic plants. Developmental and feeding performances, as well as the immediate impact of the predator when released onto A. spiraecola colonies, indicate that S. nubilus could be a useful candidate for reducing aphid populations. © 2019 Society of Chemical Industry.

Is leaf pruning the key factor to successful biological control of aphids in sweet pepper?

Aphids (Hemiptera: Aphididae) are a problematic pest in global sweet pepper cultivation. Control of aphids often relies on insecticides, leading to widespread resistance. Biological control of aphids is mainly based on releasing specialist natural enemies, but they often fail to control outbreaks. Macrolophus pygmaeus Rambur (Hemiptera: Miridae) is a zoophytophagous generalist which attacks several sweet pepper pests, including aphids. Previous research showed that M. pygmaeus is capable of strongly reducing aphid populations in sweet pepper, but complete control was seldom achieved. Sweet pepper plants continue to grow during the season, reaching > 3 m high in Belgian and Dutch greenhouses. Dense foliage and large vertical distance from the flowers to the lower leaves impede the search efficiency of the predator. Leaf pruning may improve aphid predation by M. pygmaeus by increasing the probability of encountering prey. Four and five treatments (foliage range: 100 cm to full length) respectively were tested in a semi-commercial sweet pepper greenhouse in 2017 and 2018. Aphid populations in pruned treatments grew more slowly than in the control and M. pygmaeus was eventually able to control aphids in all pruned treatments in 2018. There was no difference in aphid control between the pruned treatments. Sweet pepper production was lower in the treatments with the shortest foliage lengths. Leaf pruning up to 160 or 190 cm foliage length improves aphid control by M. pygmaeus in sweet pepper without affecting production. © 2019 Society of Chemical Industry.

Effectiveness of Tephrosia vogelii and Tephrosia candida Extracts against Common Bean Aphid (Aphis fabae) in Malawi

Common beans (Phaseolus vulgaris) remain an important dietary protein source in Malawi. However, its production is highly hindered by insect pest and disease attack. The study aimed at evaluating the effectiveness of Tephrosia vogelii and Tephrosia candida extracts against bean aphid (Aphis fabae). The evaluation involved two botanical extracts at three different concentrations (0.5%, 2%, and 5% w/v) against bean aphid. Plant extracts (leaves) were air-dried and milled. Powders were then soaked in a 2-litre plastic bucket of cold water. Results indicated that there was significant difference (P<0.05) among treatments. The effectiveness of the treatments was based on reduction in aphid population per plant, pod length, and bean yield. Pod length and bean yield were higher in T. vogelii and Karate as compared to untreated and T. candida. There was a high mortality rate of aphid on the plots treated with T. vogelii compared to plots treated with T. candida at the same concentration. Though these two plant extracts were not as effective as the synthetic insecticide in reducing aphid population, they were considerably and significantly found to be effective; hence, its use by poor-resource farmers is recommended in the protection of bean against aphid.

Wheat genotypic diversity and intercropping to control cereal aphids

Increasing intrafield plant diversity has been shown to regulate pest populations. Mixing wheat cultivars and intercropping winter wheat and white clover are both promising agroecological practices. On field experiments over two growing seasons, we combined both practices and examined the impact on aphid populations and on wheat production. Results show that combining intra- and interspecific diversity did not outperform each practice individually in reducing aphid populations. Taken separately, intercropping tended to have lower aphid infestation, while it was intermediate in cultivar mixtures. Yearly variation in climatic conditions impacted wheat and clover development, as well as the appearance of aphid peaks. Wheat yields and grain nitrogen content were reduced in intercropping by 10% and 7%, respectively, but not in cultivar mixtures. Our findings suggest that intrafield diversification may regulate wheat aphids to some extent, but combining two diversification practices did not result in an attractive trade-off between pest regulation and wheat production in real farming conditions.

Plasmid engineering of aphid alarm pheromone in tobacco seedlings affects the preference of aphids

ABSTRACTPlants producing sufficient amount of aphid alarm pheromone by expressing (E)-β-Farnesene (EβF) synthase gene may contribute to plant protection by reducing aphid populations. However, terpene biosynthesis varies among plant species and developmental stages. In the present study, volatile headspace analysis of tobacco seedlings with MaβFS1 (an EβF synthase from the Asian peppermint Mentha asiatica) failed to generate EβF. We further targeted MaβFS1 to the tobacco plastid, using a chloroplast targeting sequence, either with or without the AtFPS1 gene for the biosynthesis of the precursor farnesyl diphosphate. When both MaβFS1 and AtFPS1 genes were targeted to the chloroplast, low levels of EβF were detected in stably transformed tobacco seedlings; resulting in specific repellence of the green peach aphid, Myzus persicae. These data indicate that redirecting the EβF biosynthetic pathway from its natural cytosolic location to the chloroplast is a valid strategy. This redirecting strategy may be very useful for other crop plants that do not naturally produce EβF or other repellent volatiles.

Foliar Application of Gebbrillic and Salicylic Acids Improves Fruit Quality and Yield and Reduces Aphid Population in Pomegranate (Punica granatum L.)

Pomegranate crop suffers many problems during tree growth and fruit production stages. The pomegranate ramp, Aphis punicae (Passerini) is serious pests that attack pomegranate in Egypt. This study was carried out to examine the influence of ascorbic acid (ASA), gibbrellic acid (GA3) and salicylic acid (SA) on yield and fruit quality and aphid population in pomegranate. The application rates were (250, 500 and 1000 ppm) for ASA, 250, 500 and 1000 ppm for GA and 200, 400 and 600 ppm for SA thrice during the growing season. The foliar application of GA3 and SA improved yield (kg/tree), fruit weight (g) , fruit number/tree, fruit cracking, TSS, acidity %, TSS/acid % ratio , and reduced aphid population.

Efficacy of safer insecticides against aphid on celery

Aphids (Myzus persicae) are one of the most important pest of celery, which is cultivated for its fleshy leafstalks, seeds and essential oil. Aphids suck sap from the plant and reduce yield. Also, they transmit viral diseases and contaminate celery produce with honeydew. Some safer insecticides namely flonicamid 50 WG @ 150, 175 and 200 g/ha, imidacloprid 200 SL @ 75, 100 and 125 ml/ha, thiamethoxam 25 WG @ 75, 100 and 125 g/ha and acetamiprid 20 SP @ 37.5, 50 and 62.5 g/ha were evaluated for their efficacy against aphids. Population of aphids per inflorescence before spray varied from 12.03 to 13.20. All the treatments were significantly better than control. On all observation dates flonicamid @ 175 and 175 and 200 g/ha, imidacloprid @ 100 and 125 ml/ha, thiamethoxam @ 100 and 125 g/ha, acetamiprid @ 50 and 62.5 g/ha were statistically better in reducing aphid population than other treatments. Highest seed yield of 11.30 q/ha was obtained with flonicamid50 WG @ 200 g/ha which was statistically at par with imidacloprid 200 SL @ 100 and 125 ml/ha, thiamethoxam 25 WG @ 100 and 125 g/ha and acetamiprid 20 SP @ 50 and 62.5 g/ha and flonicamid50 WG @ 175 g/ha.

Eco-friendly management of Lipaphis erysimi (Kalt.) on Mustard crop in Varanasi region

The result revealed that among all tested essential oils from medicinal plants, the maximum reduction of aphid population over control was observed in plots treated with Cymbopogon citrates oil (85.2%) followed by Pogostemon cablin oil (82.21%). Whereas, Mentha piperita oil (58.4%) was found least effective in reducing the aphid population over control. The tested plant essential oils and insecticide on the basis of field efficacy in reducing aphid population were found in order of Cymbopogon citrates oil > Pogostemon cablin oil > Eucalyptus oil > Neem oil > Ocimum basilicum. Maximum mustard yield was obtained in the plots treated with Cymbopogon citrates oil (16.09 qha−1) and minimum with Dimethoate (9.76 qha−1) compared to the control (5 qha−1). The highest B/C ratio was found in the treatment of Neem oil (5.43: 1) whereas, the lowest B: C ratio of 3.07: 1 was obtained in Curcuma longa treated plot. Though the maximum yield was obtained from Cymbopogon citrates oil owing to its effectiveness against mustard aphid, but B/C ratio was higher with Neem oil because of differences in cost of essential oils.

Biochar applications decrease reproductive potential of the English grain aphid Sitobion avenae and upregulate defense-related gene expression.

The application of biochar as a targeted strategy for managing herbivorous pests is a topic of growing interest. The present study first determined the influence of biochar amendments on the reproductive performance of the English grain aphid Sitobion avenae, and then examined defense-related gene expression in the wheat plant as a function of biochar amendments and aphid feeding. Compared to the control, biocahr amendments decreased aphid lifetime fertility by 9.09% and 20.23% for amending levels at 3% and 5%, respectively; it reduced aphid population by 18.68%, 21.69%, and 28.70% for the levels at 1.5%, 3%, and 5%, respectively. Biochar applications increased silicon content more than 40% in wheat plants. Furthermore, biochar additions increased the expression of four defense-related genes (AOS, LOX, PAL and PR) in wheat plants with extension of feeding time by aphids. Our results suggest that biochar amendments to soils have detrimental consequences on the reproductive potential of the aphid on the wheat, and the effect may result from aphid-induced plant defenses being raised by biochar applications. © 2018 Society of Chemical Industry.

Plant growth promoting rhizobacteria reduce aphid population and enhance the productivity of bread wheat.

Plant growth promoting rhizobacteria increase plant growth and give protection against insect pests and pathogens. Due to the negative impact of chemical pesticides on environment, alternatives to these chemicals are needed. In this scenario, the biological methods of pest control offer an eco-friendly and an attractive option. In this study, the effect of two plant growth promoting rhizobacterial strains (Bacillus sp. strain 6 and Pseudomonas sp. strain 6K) on aphid population and wheat productivity was evaluated in an aphid susceptible (Pasban-90) and resistant (Inqlab-91) wheat cultivar. The seeds were inoculated with each PGPR strain, separately or the combination of both. The lowest aphid population (2.1 tiller−1), and highest plant height (85.8 cm), number of spikelets per spike (18), grains per spike (44), productive tillers (320 m−2), straw yield (8.6 Mg ha−1), and grain yield (4.8 Mg ha−1) were achieved when seeds were inoculated with Bacillus sp. strain 6 + Pseudomonas sp. strain 6K. The grain yield of both varieties was enhanced by 35.5–38.9% with seed inoculation with both bacterial strains. Thus, the combine use of both PGPR strains viz. Bacillus sp. strain 6 + Pseudomonas sp. strain 6K offers an attractive option to reduce aphid population tied with better wheat productivity.

Landscape Context Affects Aphid Parasitism by Lysiphlebus testaceipes (Hymenoptera: Aphidiinae) in Wheat Fields.

Winter wheat is Oklahoma's most widely grown crop, and is planted during September and October, grows from fall through spring, and is harvested in June. Winter wheat fields are typically interspersed in a mosaic of habitats in other uses, and we hypothesized that the spatial and temporal composition and configuration of landscape elements, which contribute to agroecosystem diversity also influence biological control of common aphid pests. The parasitoid Lysiphlebus testaceipes (Cresson; Hymenoptera: Aphidiinae) is highly effective at reducing aphid populations in wheat in Oklahoma, and though a great deal is known about the biology and ecology of L. testaceipes, there are gaps in knowledge that limit predicting when and where it will be effective at controlling aphid infestations in wheat. Our objective was to determine the influence of landscape structure on parasitism of cereal aphids by L. testaceipes in wheat fields early in the growing season when aphid and parasitoid colonization occurs and later in the growing season when aphid and parasitoid populations are established in wheat fields. Seventy fields were studied during the three growing seasons. Significant correlations between parasitism by L. testaceipes and landscape variables existed for patch density, fractal dimension, Shannon's patch diversity index, percent wheat, percent summer crops, and percent wooded land. Correlations between parasitism and landscape variables were generally greatest at a 3.2 km radius surrounding the wheat field. Correlations between parasitism and landscape variables that would be expected to increase with increasing landscape diversity were usually positive. Subsequent regression models for L. testaceipes parasitism in wheat fields in autumn and spring showed that landscape variables influenced parasitism and indicated that parasitism increased with increasing landscape diversity. Overall, results indicate that L. testaceipes utilizes multiple habitats throughout the year depending on their availability and acceptability, and frequently disperses among habitats. Colonization of wheat fields by L. testaceipes in autumn appears to be enhanced by proximity to fields of summer crops and semi-natural habitats other than grasslands.

Lecanicillium muscarium and Adalia bipunctata combination for the control of black bean aphid, Aphis fabae

The predator Adalia bipunctata (Coleoptera: Coccinellidae) and the entomopathogenic fungus Lecanicillium muscarium, have been considered as potential biological control against aphids. While it can be difficult to achieve a high control level of Aphis fabae Scopoli (Hemiptera: Aphididae) using only a single beneficial agent, the research presented here aimed to determine the interaction between L. muscarium and A. bipunctata potential for control against A. fabae. Lecanicillium muscarium was found to cause about 30% mortality in A. bipunctata and with a reduction in feeding by about 15%. However, co-application of A. bipunctata and L. muscarium can cause an addititive effect in reducing aphid populations, resulting in about 90% reduction in aphid populations compared with control treatment. Thus, these two biocontrol agents have the potential to be complementary. This research study demonstrates that it is possible to combine A. bipunctata with L. muscarium to provide a sustainable method for management of A. fabae on broad bean cropping system and that field studies are required.

Estimating parasitoid impact on aphid populations in the field

We developed a quantitative method to assess the capacity of parasitoids to reduce aphid populations in open fields. The method, designated as the propagated mortality analysis (PMA), estimates the impact of early parasitoid-induced mortality on forthcoming aphid populations and was built upon an existing model describing the bell-shaped population dynamics observed in many aphid species. The PMA was next used to assess the impact of the naturalized and most abundant parasitoid Aphelinus sp. on populations of the soybean aphid Aphis glycines under field conditions in north-eastern North America. Results from the PMA showed that Aphelinus sp. reduced both peak soybean aphid densities and cumulative aphid-days at the end of the pest management threshold period by only 1–7%, probably because of low levels of parasitism early in the season. The method we propose is simple to use, could apply to most aphid-parasitoid systems and would gain to be extended to other natural enemies.

Intercropping Kale with Culinary Herbs Alters Arthropod Diversity and Hinders Population Growth in Aphids

The aim of this work was to evaluate arthropod diversity and levels of population growth in Myzus persicae (Sulzer) under kale (Brassica oleracea L. var. acephala DC) intercropped with green onion (Allium fistulosum L.), coriander (Coriandrum sativum L.), basil (Ocimum basilicum L.), and parsley [Petroselinum crispum (Mill.) Nym.]. The following characteristics were evaluated under both monocrop and intercrop systems: 1) arthropod diversity and abundance, 2) population growth rate in the M. persicae aphid, 3) average number of aphids per kale leaf, and 4) total fresh weight of produced kale. The experiment was carried out in Fortaleza, in the state of Ceará, Brazil, in a design of randomized blocks, with five treatments and five replications. The family Aphididae was the most abundant, represented by M. persicae. Thirty-nine spiders were the most abundant predators. The intercrop with basil gave the greatest diversity of arthropods. The aphid population showed slower growth under the intercrop systems with cilantro and with parsley. Fresh weight production in the kale was inversely proportional to the number of aphids on the plants. The results suggest that intercropping kale with culinary herbs is a promising strategy to reduce aphid populations and losses occasioned by them.

Efficacy of some Medicinal Plant Oils against Cabbage Aphid, Brevicoryne brassicae L. On Cabbage

Field experiments were carried out at Vegetable Research Farm, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi U.P. during the year 2016–17 to control the Bravicoryne brassicae in cabbage variety Golden acre. result revealed that Among the all the essential medicinal plant oils the maximum reduction of aphid population over control was observed in plots treated with Citronella oil (85.25%) followed by Pogostemon cablin oil (80.21%). Whereas, Mentha oil (58.48%) was found least effective in reducing the aphid population over control. The tested plant essential oils and insecticide on the basis of field efficacy in reducing aphid population are found in order of Citronella oil > Patchouli oil > O. basilicum var. saumya > Palmarosa oil > O. basilicum var. Surabhi > O. basilicum × O. tenuiflorum > Asataf > Turmeric oil > Mentha oil. The effect of different essential oils on cabbage yield was also studied under investigation; and maximum yield of cabbage heads was obtained in the plots treated with Citronella oil (233.89 qha−1) and Minimum yield obtained menthe oil (217.22 qha−1) Over the control and then The highest B/C ratio was found in the treatment of Cymbopogon martinii 0.05%(31.27: 1) whereas, the lowest B: C ratio of 17.70: 1 was obtained in Mentha oil treated plot followed by Curcuma longa 0.1% (22.82: 1). Though the maximum yield was obtained from plots treated with Cymbopogon citrates oil. However, the highest B/C ratio was obtained from the plots treated with Cymbopogon martinii oil. This is so, because of differences in cost of essential oils.

Evaluating the Impact of Border Crops on Aphid (Hemiptera: Aphididae) Infestation and Damage in Butternut Squash ( Cucurbita moschata )

Aphids cause loss of quality and value in butternut crops due to pest injury and the transmission of viruses in a non-persistent manner. A field experiment was conducted in Daylesford, Gweru in August 2012/2013 planting season to evaluate border cropping practice as a management strategy for aphid infestation and damage in butternut squash (Cucurbita moschata). The experiment was arranged as a 2 x 2 + 1 factorial in a randomised complete block design (RCBD) replicated 4 times. Treatments were Maize (Zea mays) border planted at 25 000 and 45 000 plants/ha and sorghum (Sorghum bicolor) border planted at 200 000 and 260 000 plants/ha plus a butternut crop with no border (control). All borders were planted 0.5 m from the butternut crop. Data on aphid counts on borders and on butternuts, disease incidence, yield and land equivalent ratio for the intercrops was recorded. Results showed that, border crops and border density interacted significantly (p < 0.05) to to reduce aphid population, disease incidence and yield of butternuts. From the results, butternut plots bordered by maize at 45 000 plants/ha recorded the highest butternut yield (16t/ha), least aphid population and least viral disease incidence during the 7th week after planting when compared to control. Based on these findings it can be concluded that the use of maize border cropping at 45 000 plants/ha can be effective in controlling aphids in butternuts.

Pest regulation and support of natural enemies in agriculture: Experimental evidence of within field wildflower strips

Restoring ecosystem services in agriculture is vital to reach a sustainable food production. More specifically, developing farming practices which enhance biological pest control is a main issue for today’s agriculture. The aim of this study was to assess whether the two strategies of complicating the search of host plants by pests by increasing plant diversity, and of supporting their natural enemies by managing habitats, could be combined simultaneously at the field scale to restore biological pest control and reduce chemical insecticide use. In Gembloux (Belgium), wildflower strips (WFS) were sown within wheat crops in which pests (i.e., aphids), their predators (i.e. aphidophagous hoverflies, lacewings and ladybeetles) and parasitoid wasps were monitored for 10 weeks in the period of May through July 2015 as indicators of the ES of pest control. Aphids were significantly reduced and adult hoverflies favoured in wheat in between WFS, compared to monoculture wheat plots. No significant differences were observed for adult lacewings, ladybeetles and parasitoids. In all treatments, very few lacewing and ladybeetle larvae were observed on wheat tillers. The abundance of hoverfly larvae was positively correlated with the aphid density on tillers in between WFS, showing that increasing food provisions by multiplying habitats within fields, and not only along margins, can help supporting aphidophagous hoverflies in crops. By enhancing the ecosystem services of biological pest control, this study shows that increasing both plant diversity and managing habitats for natural enemies may reduce aphid populations, hence insecticide use. Future research should continue this vein of work by quantifying the link between agricultural practices and the delivery of ecosystem services in order to guide future measures of agricultural policies.

Aphid vectors of Papaya ringspot virus and their weed hosts in orchards in the major papaya producing and exporting region of Brazil

Papaya ringspot, one of the most important diseases of papaya, is caused by Papaya ringspot virus type P (PRSV-P), which is transmitted by various aphid species. Objectives of this research were to identify the aphid species and their weed hosts of papaya orchards in the major papaya producing and exporting region of Brazil in northern Espírito Santo State. Aphids were collected from weed hosts, and with Möericke-type traps in papaya orchards of twenty farms in Linhares, Sooretama and Aracruz municipalities of Espírito Santo, Brazil. A total of forty aphid species were collected, of which 22 are new records in the State. Thirty-eight aphid species were identified from traps, including Aphis craccivora Koch, A. gossypii Glover, A. spiraecola Patch, Myzus persicae (Sulzer), and Toxoptera citricidus (Kirkaldy), known vectors of PRSV-P. Cryptomyzus Oestlund (Aphididae) is recorded for the first time in Brazil. Thirteen aphid species associated with 22 weed species of 14 families were collected. Aphis gossypii, which has been reported to be one of the most efficient vectors of PRSV-P, infested the greatest number of weed hosts. Chamaesyce hyssopifolia (L.) Small, Euphorbia hirta L. (Euphorbiaceae), Commelina benghalensis L. (Commelinaceae), Lepidium virginicum L. (Brassicaceae) and Sida sp. (Malvaceae) were the most frequently infested weeds. Commelina benghalensis was infested by the greatest number of aphid species during this study. Integrated management of weed hosts of aphids to reduce aphid populations in papaya orchards may be useful for control of PRSV-P. Based on accurate knowledge of the aphid and weed species present in papaya orchards obtained in this study, integrated pest management efforts may be more efficiently directed toward eliminating the most frequently infested weed species that serve as hosts for aphid vectors of PRSV-P.

Laboratory and field studies demonstrating the insecticidal potential of diatomaceous earth against wheat aphids in rice-wheat cropping system of Punjab (India)

Aphids have acquired the status of major pest in North-western plains of India. A complex of five species infests the wheat in this part of the country. The diatomaceous earth (DE) has the potential to substitute the most widely used method of chemical control. Laboratory and field investigations were conducted to evaluate the effectiveness of DE either as soil or foliar application for suppression of wheat aphids during 2013–2014 and 2014–2015. The fecundity, adult longevity and total developmental duration of Rhopalosiphum padi decreased with the increasing dosage of soil application of DE in laboratory evaluation. However in field studies, no significant difference in aphid population was observed among different levels of DE application in soil. Foliar application of DE 150 kg/ha and higher dosages significantly reduced aphid population for initial two days but thereafter it had no effect on aphid prevalence. Wheat plant dusted with different dosages of DE did not show any visible injury but the reduction in chlorophyll content was observed in them. Overall, poor field efficacy coupled with loss of chlorophyll and safety issues relating to foliar application of DE proved against its use for control of sucking insect pests.

Differential Reactions of Soybean Isolines With Combinations of Aphid Resistance Genes Rag1 , Rag2 , and Rag3 to Four Soybean Aphid Biotypes.

With the discovery of the soybean aphid ( Aphis glycines Matsumura) as a devastating insect pest of soybean ( Glycine max (L.) Merr.) in the United States, host resistance was recognized as an important management option. However, the identification of soybean aphid isolates exhibiting strong virulence against aphid resistance genes ( Rag genes) has highlighted the need for pyramiding genes to help ensure the durability of host resistance as a control strategy. In this study, soybean isolines with all possible combinations of the resistance and susceptibility alleles at Rag1 , Rag2 , and Rag3 were evaluated for their effectiveness against the four characterized soybean aphid biotypes. All soybean isolines, including the susceptible check carrying none of the resistance alleles (S1/S2/S3), were infested with each biotype in no-choice greenhouse tests, and the aphid populations developed on each isoline were enumerated 14 d after infestation. All gene combinations, with the exception of Rag3 alone, provided excellent protection against biotype 1. Isolines with Rag2 alone or in combination with Rag1 and Rag3 had greater levels of resistance to biotype 2 than those with either Rag1 alone, Rag3 alone, or the Rag1/3 pyramid. For biotype 3, the Rag1/3 and Rag1/2/3 pyramided lines significantly reduced aphid populations compared with all other gene combinations, while the Rag1/2/3 pyramid provided the greatest protection against biotype 4. Overall, the Rag1/2/3 pyramided line conferred the greatest protection against all four biotypes.