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Crop wild relatives (CWRs) have high levels of genetic diversity compared to their domesticated descendants. Soybean (Glycine max) has over 20 species of CWRs, most of which are in secondary and tertiary gene pools. Glycine soja, hereafter ‘soja,’ is the only wild relative in the primary gene pool, i.e., species that readily cross with soybean. Soja has many advantageous traits that may be transferrable to soybean, including resistance to insect pests, with particularly strong sources of resistance to the soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae). Soybean aphid has been a major soybean pest in the United States and Canada since 2000 and a longstanding pest in East Asia. This paper reviews the challenges of developing soybean with durable resistance to soybean aphid in light of multiple, virulent biotypes in North America and China. It also examines particular challenges in evaluating soja germplasm for soybean aphid resistance and resultant solutions to those challenges. Soja germplasm is widely available, but from our experience, the logistics associated with reliably procuring high-quality soja seed has posed the main challenge in working with this CWR. This review highlights soja accessions identified with strong resistance to soybean aphid and their genetic bases, and it discusses possible strategies for exploiting aphid-resistant soja accessions to improve soybean pest management.

The soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), remains an important pest of soybean, Glycine max (L.) Merr., in areas of the Midwestern United States and southern Canada. Options for managing soybean aphid are currently limited to insecticides and aphid-resistant varieties. Farmers commonly employ a prophylactic treatment of soybean seed with a neonicotinoid insecticide such as thiamethoxam and often a remedial, late-season application of foliar insecticides such as the pyrethroid, λ-cyhalothrin. Environmental concerns about detrimental side effects of neonicotinoids and the substantiation of pyrethroid resistance in field populations of soybean aphid have strengthened the case for planting aphid-resistant soybean cultivars. We conducted a three-year field study in eastern South Dakota, United States, that evaluated commercially-available active substances and enhanced plant materials for soybean aphid management that included a thiamethoxam seed treatment, spray application of λ-cyhalothrin, and an aphid-resistant soybean cultivar containing a pyramid of the Rag1 and Rag2 aphid-resistance genes. Soybean aphid infestations had sustained, economically injurious levels in 2015, but not the other two years. The three management tactics independently reduced soybean aphid population densities. Thiamethoxam and the resistant cultivar suppressed cumulative aphid-days (CAD) in all three years, whereas the λ-cyhalothrin spray decreased CAD in 2015 and 2017. By far, the resistant cultivar had the greatest impact on soybean aphid populations, reducing CAD by 28- to 150-fold year−1, with mean numbers of aphids much less than 100 soybean aphids plant−1. Thiamethoxam seed treatment reduced CAD by 1.7- to 3.5-fold year−1, and λ-cyhalothrin reduced it from 2.0- to 5.6-fold year−1. Soybean yield was not affected by treatments in 2015. Yield was greater for the susceptible than for the resistant cultivar in 2016, and yield was greater for plots without foliar insecticide in 2017. Implications for the use of these management tactics against soybean aphid are discussed.

The soybean aphid (Aphis glycines) is an important pest of soybean (Glycine max). Wild soybean (Glycine soja; also known as ‘soja’) has many useful traits, including some accessions with aphid resistance that may be incorporated into modern soybean cultivars. The objective of this work was to evaluate 76 selected soja accessions and 14 associated soybean accessions for resistance against two virulent colonies of soybean aphid in environmental-chamber experiments. In free-choice tests, soja accessions PI 407175, PI 407190, PI 407206, PI 407240, PI 507624 and PI 562558 were resistant against the Accrue colony, and PI 407191wf and PI 597458 C were resistant against the Volga16 colony. None of the soybean test accessions except the resistant check, PI 437696, showed resistance against either colony in free-choice tests. In no-choice tests, soja accession PI 507624 showed strong resistance against the Accrue colony; whereas PI 407240 and PI 407190 had intermediate aphid levels; PI 597458 C showed strong resistance to Volga16 aphids, and PI 407191wf had an intermediate level of resistance. Based on results from both sets of tests, soja accessions PI 507624 and PI 597458 C may be strong candidates in breeding programs to develop aphid-resistant soybean cultivars.

The soybean aphid (Aphis glycines Matsumura) is a major pest of soybean (Glycine max (L.) Merr.) in eastern Asia and in North America. Aphid-resistant soybean cultivars have been developed as a non-chemical management tactic, but viability of this tactic may depend on the availability of diverse resistance sources, including wild soybean (Glycine soja Siebold and Zucc.), in order to counter various resistance-breaking soybean aphid biotypes. In this study, 10 wild soybean accessions were identified as resistant in free-choice screening assays against avirulent soybean aphid biotype 1, and eight of the accessions were advanced for follow-up in two, 20-day-long no-choice assays. Two accessions, PI 65549 and PI 135624, did not differ from resistant check PI 549046 in number of aphids per plant after 10 and 20 days of infestation; accessions 99PI101404B, PI 549035 B, and PI 342618 A had more aphids than PI 549046 by day 20, but fewer aphids than known susceptible accessions. In a second no-choice assay, accessions 99PI81762 and PI 101404 A had fewer aphids than other test accessions but more aphids than PI 549046 by day 20. Because of particularly strong resistance in PI 135624 and PI 65549, these two accessions should be genetically characterized and tested for resistance against virulent soybean aphid biotypes.

Soybean aphid (Aphis glycines Matsumura; SA) is a major invasive pest of soybean [Glycine max (L.) Merr.] in northern production regions of North America. Although insecticides are currently the main method for controlling this pest, SA-resistant cultivars are being developed to sustainably manage SA in the future. The viability of SA-resistant cultivars may depend on identifying a diverse set of resistance genes from screening various germplasm sources, including wild soybean (Glycine soja Siebold and Zucc.), the progenitor of cultivated soybean. Data consisted of infestation ratings generated for a total of 337 distinct plant introduction lines of wild soybean that were exposed to avirulent SA biotype 1 for 14 d in 25 separate tests. Individual plants of the test lines were given a common rating by two researchers, based on a rating scale that progressed from 1=0 to 50, 2=51 to 100, 3=101 to 150, 4=151 to 200, 5=201 to 250, and 6 with >250 SA per test plant. Public dissemination of this dataset will allow for further analyses and evaluation of resistance among the test lines. Keywords: Crop ancestors, Resistance screening, Host-plant resistance

The soybean aphid (SA), Aphis glycines Matsumura, is a major pest of soybean in the north-central United States and south-central Canada. It is controlled primarily with insecticides, but the development of aphid-resistant soybean cultivars may provide an alternative management tactic. The viability of this management tactic depends on a diverse set of resistance sources in order to counter various resistance-breaking biotypes of SA, and the identification of new sources of resistance necessitates additional testing of soybean germplasm. The current study used no-choice tests to identify SA resistance in seven early maturing (maturity group I) soybean plant introductions (PIs) that had been advanced from free-choice screening trials. The tests showed PI 437353 and PI 612759 C had an intermediate level of resistance against avirulent SA, whereas PI 437282, PI 437658, PI 437733, PI 548417, and PI 548530 exhibited no significant resistance. Additional research is needed to determine if the source of resistance in PI 437353 and PI 612759 C is due to novel resistant genes, which would help diversify resistance to SA in soybean. Screening and follow-up tests of additional soybean germplasm is warranted in order to ensure the development of durable, SA-resistant cultivars.

Soybean aphid (Aphis glycines Matsumura) is a pest of soybean [Glycine max (L.) Merr] in the Midwestern U.S. and southern Canada. Host plant resistance provides an alternative to insecticides for soybean aphid management. Soybean with Rag1 + Rag2 aphid resistance is available commercially but does not protect against soybean aphid biotype 4 colonization. To find sources of resistance to soybean aphid biotype 4, we turned to soybean’s progenitor Glycine soja (Sieb. and Zucc.). Twenty soja plant introductions (PIs) with previously identified resistance to avirulent soybean aphid biotype 1 were assessed in free-choice tests against biotype 4, followed by a no-choice test for promising PIs. Experiments were repeated using three soybean aphid biotype 4 colonies, collected from separate site-years (Lomira, WI 2013; Volga, SD 2015, 2016). Free-choice tests identified six, three, and eight soja PIs with putative resistance to Lomira13, Volga15, and Volga16 aphid colonies, respectively. No-choice tests identified six, two, and six soja PIs that continued to suppress Lomira13, Volga15, and Volga16 aphids, respectively. PI 65549 and PI 101404A were resistant to each of the three colonies of soybean aphid biotype 4 and may contribute to durable resistance against soybean aphid.

Soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), infestations of soybean, Glycine max (L.) Merr. (Fabales: Fabaceae), and the associated yield loss have led to a large dependence on insecticidal management in soybean throughout the Midwestern United States. However, several populations of pyrethroid-resistant soybean aphids have recently been found in Iowa, Minnesota, North Dakota and South Dakota, which highlights the importance of alternative management approaches. One such alternative method is host-plant resistance, which uses naturally occurring plant defenses in crop cultivars to reduce the potential for yield loss from a pest population. Current soybean aphid-resistant cultivars do not protect against all soybean aphids due to the presence of virulent biotypes. In particular, soybean aphid biotype 4 is virulent to Rag1 and Rag2 resistance genes both individually and in combination. However, we hypothesized that resistance to biotype 4 may exist in previously identified, but uncharacterized resistant soybean plant introductions (PIs). To test this, we evaluated 51 previously identified but uncharacterized soybean aphid-resistant PIs for their resistance to colonies of soybean aphid biotype 4 collected in separate site-years (Lomira, WI 2013; Volga, SD 2015, 2016). Free-choice tests identified 14 PIs with putative resistance to ‘Lomira13’, two to ‘Volga15’, and eight to ‘Volga16’ soybean aphid colonies. Follow-up, no-choice tests corroborated two to three resistant PIs per colony, and PI 437696, which was resistant to each of the three colonies and could aid in breeding efforts and an integrated approach to soybean aphid management.

The use of neonicotinoid insecticides in the United States has grown by about a factor of four since the mid-2000s. Seed treatments account for a significant fraction of overall insecticide application to crops, and a large proportion of major U.S. crops are now planted using seed treated with neonicotinoids. Neonicotinoid insecticidal seed treatments are primarily intended to protect crops against sporadic or minor early-season pests. A better understanding of factors that influence the risk of economic infestations and extent of crop damage by sporadic pests is needed to target neonicotinoid insecticidal seed treatments use based on expected pest pressure. In a series of papers, we review the distribution, ecology, and historical management of seed and seedling pests targeted by neonicotinoid seed treatments in U.S. corn (Zea mays), soybean (Glycine max), wheat (Triticum aestivum), and cotton (Gossypium hirsutum L.). This information is key to region-specific management practices that reduce the risks and increase the benefits of neonicotinoid seed treatments.

The use of insecticides at planting has been a common crop management practice in cotton for several decades. Historically, U.S. cotton growers relied on in-furrow applications of insecticides, such as aldicarb, to control early-season insect pests. In-furrow applications have largely been replaced with insecticide-treated seed. Since 2012, more than 60% of the U.S. cotton crop is planted with seed treated with insecticide, primarily the neonicotinoids imidacloprid or thiamethoxam. Several insects or insect groups are included on the labels of these neonicotinoids for use as seed treatments. An increased understanding of the risks associated with economically injurious populations of insect pests is needed to optimize use of early-season insecticides and reduce over-reliance on them in cotton, especially when initial decisions for insect control before planting have subsequent influence on future pest abundance. Existing literature pertaining to these early-season cotton insect pests was examined to identify factors favoring their distribution and abundance and the importance of insect control tactics used at planting. The relative importance of some of these pests is dependent on the cotton-growing region and impacted by local production practices. Thrips (predominantly Frankliniella spp.) (Thysanoptera: Thripidae) are the most prevalent early-season insect group in cotton across the United States and the primary target of initial insect control. Other targeted insects include the black cutworm, Agrotis ipsilon (Hufnagel) (Lepidoptera: Noctuidae), aphids (predominantly Aphis gossypii Glover) (Hemiptera: Aphididae), plant bugs (Hemiptera: Miridae), and wireworms (Coleoptera: Elateridae).

A preventative insecticide treatment is a tactic compatible with an integrated pest management (IPM) strategy for a particular pest only when a rescue treatment is not a realistic option, and if there is a reasonable expectation of economic damage by that pest. Most corn, Zea mays L., planted in the United States is protected from several sporadic early-season insect pests by neonicotinoid seed treatments, usually without the knowledge of the threat posed in a given field. We undertook an extensive literature review of these sporadic pests to clarify the prevalence of economic infestations in different regions of the United States, and the agronomic, biotic, and abiotic factors that affect the likelihood of attack. The summaries of the prevalence and risk factors presented here should help farmers and consultants better assess the value of preventative protection of seedling corn under local conditions, and provide others with a better understanding of the complexities farmers face in assessing risks posed by potential pests. The profiles suggest that, in general, pressure from most sporadic pests on seedling corn is rare or local, seldom high enough to decrease yield. However, this is not true in all regions for all sporadic pests. An important issue exposed by the profiles is that the value of preventative insecticide protection of seedling corn depends on understanding the likely combined pressure from multiple species. While such risk may often still be negligible, there is a great need for robust methodology to assess the risk posed by multiple pests. This represents a significant challenge for future research.

The Hessian fly, Mayetiola destructor (Say) (Diptera: Cecidomyiidae); cereal aphids (Hemiptera: Aphididae); and wireworms (Coleoptera: Elateridae) are three common and important insect pests of seedling wheat, Triticum aestivum L., in the United States. Though less common as pests, false wireworms (Coleoptera: Tenebrionidae) may also be problematic in situations that favor wireworms. In addition, cereal aphids vector viruses that cause barley yellow dwarf, a serious and widespread wheat disease. Scientific journal publications, review articles, and management guidebooks on wheat insect pests were consulted to determine the extent and intensity that these pests impose on wheat production in the United States. Widespread outbreaks occur infrequently, but local outbreaks happen nearly every year for the three major pests and cause several millions of dollars in crop losses annually. Hessian fly perennially threatens wheat in the southeastern United States, and wireworms are persistent pests in northwestern wheat-production systems. Otherwise, the particular location and severity of outbreaks vary yearly and are largely unpredictable. However, particular agronomic practices can greatly reduce risk of infestation such as elimination of volunteer wheat and weedy hosts and planting wheat during periods of reduced pest abundance. In addition, resistant cultivars can limit Hessian fly and Russian wheat aphid (Diuraphis noxia [Kurdjumov]) damage in some areas, but virulent biotypes of each pest complicate their management. Although several preemptive tactics reliably suppress infestations and barley yellow dwarf severity, they are not compatible in all agricultural systems. Consequently, insecticides are necessary in certain areas and within particular production systems to manage major early-season insect pests of wheat.

Flowering oilseed crops have the potential to diversify agroecosystems currently dominated by corn and soybeans and improve the provision of ecosystem services such as pest control. Nectar and pollen feeding may increase natural enemy fitness and searching behaviour, increasing their survival and prey consumption rates. The soybean aphid (Aphis glycines Matsumura; Hemiptera: Aphididae) is a particularly widespread and costly agricultural pest. In this study, we evaluate the effects of two flowering oilseed crops, cuphea and calendula, on the survival of the insidious flower bug (Orius insidiosus Say; Hemiptera: Anthocoridae) and its consumption levels of A. glycines placed on soybean plants. We also evaluated the survival of O. insidiosus when placed on glandular and non-glandular cuphea varieties. The amount of A. glycines that remained unconsumed by O. insidiosus did not differ among treatments. Because mortality levels of O. insidiosus were higher on glandular compared to non-glandular cuphea p...

Soybean aphid (Aphis glycines Matsumura) (Hemiptera: Aphididae) is a major pest of soybean in northern production regions of North America, and insecticides have been the primary management approach while alternative methods are developed. Knowledge of arthropod natural enemies and their impact on soybean aphid is critical for developing biological control as a management tool. Soybean is a major field crop in South Dakota, but information about its natural enemies and their impact on soybean aphid is lacking. Thus, this study was conducted in field plots in eastern South Dakota during July and August of 2004 and 2005 to characterize foliar-dwelling, arthropod natural enemies of soybean aphid, and it used exclusion techniques to determine impact of natural enemies and ants (Hymenoptera: Formicidae) on soybean aphid densities. In open field plots, weekly soybean aphid densities reached a plateau of several hundred aphids per plant in 2004, and peaked at roughly 400 aphids per plant in 2005. Despite these densities, a relatively high frequency of aphid-infested plants lacked arthropod natural enemies. Lady beetles (Coleoptera: Coccinellidae) were most abundant, peaking at 90 and 52% of all natural enemies sampled in respective years, and Harmonia axyridis Pallas was the most abundant lady beetle. Green lacewings (Neuroptera: Chrysopidae) were abundant in 2005, due mainly to large numbers of their eggs. Abundances of arachnids and coccinellid larvae correlated with soybean aphid densities each year, and chrysopid egg abundance was correlated with aphid density in 2005. Three-week cage treatments of artificially infested soybean plants in 2004 showed that noncaged plants had fewer soybean aphids than caged plants, but abundance of soybean aphid did not differ among open cages and ones that provided partial or total exclusion of natural enemies. In 2005, plants within open cages had fewer soybean aphids than those within cages that excluded natural enemies, and aphid density on open-cage plants did not differ from that on noncaged plants and those accessible by small predators. In a separate 3-yr experiment, exclusion of ants from soybean plants did not lead to differences in soybean aphid density compared with ant-accessible plants. Overall, these results suggest that the soybean aphid natural enemy guild is unsaturated and could be enhanced to improve biological control of soybean aphid in South Dakota.

The soybean aphid, Aphis glycines Matsumura, is frequently a serious pest of soybean in the U.S. and Canada, and an occasional pest of soybean throughout its native range in Asia. Large infestations of this aphid cause economic loss to soybean by reductions in seed yield and oil concentration. Host-plant resistance is a potential alternative to insecticides for managing soybean aphid, and various sources may be evaluated, including adapted cultivars, landraces, and wild ancestors of the crop. To date, few studies have evaluated wild soybean for resistance to soybean aphid. In this study, initial screening assays indicated 20 wild soybean lines with resistance to soybean aphid, and three of the 20 lines had notable resistance in subsequent choice and no-choice assays. Significantly fewer soybean aphids settled on lines PI 468397 A and PI 479749 than on susceptible lines in choice assays, and aphid populations were low and moderately low on these two respective lines in no-choice assays. Populations of soybean aphid on a third line, PI 549046, were equal to or less than those on a resistant check over 3 wks in a no-choice assay. Based on results of the respective choice and no-choice assays, resistance to soybean aphid was manifested as both antixenosis and antibiosis in PI 468397 A and PI 479749, and as antibiosis in PI 549046. This is apparently the first report of resistance to soybean aphid in these three lines, and they provide soybean breeders and pest management practitioners new sources for developing aphid-resistant soybean lines.

The soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is an invasive insect pest of soybean [Glycine max (L.) Merr. (Fabaceae)] in North America, and it has led to extensive insecticide use in northern soybean-growing regions there. Host plant resistance is one potential alternative strategy for managing soybean aphid. Several Rag genes that show antibiosis and antixenosis to soybean aphid have been recently identified in soybean, and field-testing and commercial release of resistant soybean lines have followed. In this article, we review results of field tests with soybean lines containing Rag genes in North America, then present results from a coordinated regional test across several field sites in the north-central USA, and finally discuss prospects for use of Rag genes to manage soybean aphids. Field tests conducted independently at multiple sites showed that soybean aphid populations peaked in late summer on lines with Rag1 or Rag2 and reached economically injurious levels on susceptible lines, whereas lines with a pyramid of Rag1 + Rag2 held soybean aphid populations below economic levels. In the regional test, aphid populations were generally suppressed by lines containing one of the Rag genes. Aphids reached putative economic levels on Rag1 lines for some site years, but yield loss was moderated, indicating that Rag1 may confer tolerance to soybean aphid in addition to antibiosis and antixenosis. Moreover, no yield penalty has been found for lines with Rag1, Rag2, or pyramids. Results suggest that use of aphid-resistant soybean lines with Rag genes may be viable for managing soybean aphids. However, virulent biotypes of soybean aphid were identified before release of aphid-resistant soybean, and thus a strategy for optimal deployment of aphid-resistant soybean is needed to ensure sustainability of this technology.

Although most pests of soybeans, Gycine max (L.), in the Northern Great Plains are managed using pesticides, farm management practices that encourage biodiversity offer promising long-term, sustainable solutions for controlling insect and weed pests profitably. The recent invasion of the Northern Great Plains by the soybean aphid (Aphis glycines Matsumura; Hemiptera: Aphididae) has had potentially important implications for insect communities in soybeans of this region, although recent descriptions of this regional community are scarce. We describe how three pest management systems that vary in the intensity with which they rely on herbicides and insecticides (chemically intensive, reduced chemical, and spring cover crop treatments) affect insect pest populations, arthropod predator communities, weed assemblages, and soybean yield and profitability. Soybean aphids exceeded economic thresholds in all three years, and insecticides successfully suppressed these outbreaks in the two chemical treatments; aphids exceeded the economic injury level in the cover crop treatment in two of three study years. Bean leaf beetle (Cerotoma trifurcata Forster; Coleoptera: Chrysomelidae) populations were sub-economic in all treatments; insecticides targeting soybean aphid also reduced bean leaf beetles in the first year of study when beetle populations were at their highest. Foliar-dwelling predator populations were substantially higher in the cover crop treatment than in the chemical treatments in all years of study; population declines in the latter treatments were strongly associated with insecticide applications targeting soybean aphids. Foliar predator populations did not rebound within the growing season after insecticides were applied. Soil predator populations were largely unaffected by treatment (except in 2006, when they were more abundant in the cover crop treatment than in the chemical treatments). Weed communities varied among treatments and study years, with few consistent trends except that the chemically intensive treatment had lower weed densities than the other treatments. Although input costs of the cover crop and reduced chemical treatments were lower than the chemically intensive treatment, the chemically intensive treatment was the most profitable of the three. Nevertheless, we contend that the cover crops can be managed more efficiently in order to increase the profitability and competitiveness of this treatment while gaining the long-term benefits gleaned from conserving biodiversity in our agroecosystems. Published by Elsevier Ltd.

The soybean aphid, Aphis glycines Matsumura, has become a serious pest of soybean [Glycine max (L.) Merr.] in North America, and host-plant resistance is one potential management tool. In the current study, various F2-derived soybean selections with the Rag1 gene for resistance to soybean aphid were evaluated among F2-derived soybean selections without Rag1 and among contemporary soybean lines in a two-year field test. Overall, aphid levels per plant were over tenfold greater in 2006 than in 2005, but lines generally performed similarly relative to one another between years with regard to aphid-infestation levels. In both years, the Rag1 selections ILL4, ILL27, ILL35, ILL37, ILL64RR, ILL76RR, and ILL77RR had the lowest mean number of soybean aphids per plant. In 2005, three putative Rag1 selections—ILL26, ILL67RR, and ILL87—had intermediate aphid infestation levels greater than those of other Rag1 selections, and in 2006 ILL26 and ILL67RR also had intermediate aphid levels that did not differ from all oth...

The soybean aphid, Aphis glycines, is a pest of soybean in Asia, and it has become a major pest of this crop in North America with large outbreaks that cause significant yield loss. Host-plant resistance is one management tactic being developed against soybean aphid in North America, and resistance may be manifested as antixenosis, antibiosis, or tolerance. In this study, choice tests were conducted to identify antixenosis to soybean aphids in several soybean lines. The soybean lines 'Dowling,' PI 230977, 'Jackson,' 'Cobb' and 'Palmetto' had strong antixenosis to soybean aphid, and lines PI 71506, G93-9223, 'Braxton,' 'Cook,' 'IAC-1,' 'Ripley,' and 'Tie feng 8' were moderately antixenotic. The intermediate level of antixenosis in PI 71506 contrasts with previous results, and suggests biotypic differences in the responses of soybean aphid to this line. Shoot length, shoot width, and seedling dry mass were also measured to test for any association between aphid host choice and plant size. Plant-size parameters varied by soybean line in all tests. However, the relation between aphid host choice and plant-size parameters was generally weak and not consistent across tests, suggesting that other undetermined plant characteristics were important in host selection. The identification of antixenosis in several soybean lines provides soybean breeders and pest management practitioners with additional options for managing soybean aphid through host-plant resistance. Antixenosis may be important on its own, and it may prove be complimentary to the antibiosis mode of resistance by reducing selection on resistance-breaking biotypes of soybean aphid, thereby prolonging the usefulness of plant resistance as a non-chemical means of managing soybean aphid.

Soybean aphid [ Matsumura (Hemiptera: Aphididae)] is the most damaging insect pest of soybean [ (L.) Merr.] in the Upper Midwest of the United States and is primarily controlled by insecticides. Soybean aphid resistance (i.e., genes) has been documented in some soybean accessions but more sources of resistance are needed. Incorporation of the resistance into marketed varieties has also been slow. Genome-wide association mapping can aid in identifying resistant accessions by correlating phenotypic data with single nucleotide polymorphisms (SNPs) across a genome. Aphid population measures from 2366 soybean accessions were collected from published studies screening cultivated soybean () and wild soybean ( Siebold & Zucc.) with aphids exhibiting Biotype 1, 2, or 3 characteristics. Genotypic data were obtained from the SoySNP50K high-density genotyping array previously used to genotype the USDA Soybean Germplasm Collection. Significant associations between SNPs and soybean aphid counts were found on 18 of the 20 soybean chromosomes. Significant SNPs were found on chromosomes 7, 8, 13, and 16 with known genes. SNPs were also significant on chromosomes 1, 2, 4 to 6, 9 to 12, 14, and 17 to 20 where genes have not yet been mapped, suggesting that many genes remain to be discovered. These SNPs can be used to determine accessions that are likely to have novel aphid resistance traits of value for breeding programs.

The soybean aphid, Aphis glycines Matsumura, is a serious pest of soybean [Glycine max (L.) Merr.] in the USA and Canada, and a sporadic pest of soybean in Asia. Infestations by soybean aphid cause economic loss to soybean through reductions in seed yield and oil concentration. Aphid-resistant soybean lines are needed to supplant insecticides for managing soybean aphid, and resistant lines may be developed from both domesticated and wild soybean lines. Free-choice assays of 42 lines of wild soybean (Glycine soja Siebold and Zucc.) in this study identified line 99PI522233 as resistant to soybean-aphid biotype 1. That line was advanced for follow-up assays with wild soybean lines PI 469399 B, PI 507825, PI 507840 and PI 507843, which had previously been screened as aphid resistant. Line 99PI522233 had significantly fewer soybean aphids than other lines except the resistant check in the second and third weeks of a no-choice assay, but the four other putatively resistant lines did not show resistance in the no-choice assay. Thus, line PI99522233 may be advanced for genetic characterization of its resistance, and it should be tested for resistance against virulent soybean aphid biotypes.

The direct effects of three soybean parentages, each represented by an Aphis glycines-resistant and susceptible isoline, on the fitness and performance of two key predators (Orius insidiosus and Harmonia axyridis) were evaluated in the laboratory. Predators were reared from hatch through adulthood in Petri dishes with cut trifoliolate leaves of the designated soybean variety, using eggs of Ephestia kuehniella as surrogate prey to eliminate prey-mediated effects of the host plant. Preimaginal survival and development, sex ratio, adult longevity, fecundity, and size were compared among treatments and a no-plant control. An additional experiment compared life-history parameters of predators caged with soybean versus Ipomoea hederacea (ivyleaf morning glory). Aphid resistance reduced the adult longevity of H. axyridis, but O. insidiosus was unaffected by resistance traits. However, adult O. insidiosus lived longer on soybeans with Group C base genetics than the other soybean varieties. Other parameters were not affected by soybean base genetics or resistance, but both predators generally performed worse on soybean than on I. hederacea or no-plant controls. The results suggest that soybean varietal selection, particularly with respect to A. glycines-resistance, may directly affect biological control agents. Also, implications of the generally poor suitability of soybean for natural enemies are discussed within the context of current crop production practices.

The soybean aphid, Aphis glycines Matsumura, is a pest of soybean [Glycine max L. (Merrill)] in Asia, and its recent establishment in North America has led to large, recurring outbreaks that have challenged pest management practitioners there to seek environmentally responsible means for its control. Growth-chamber experiments were conducted to determine and characterize host-plant resistance among several soybean accessions. Soybean plants were first screened for resistance by rating the population growth of A. glycines in two tests. All plants of PI 230977 and 25% of PI 71506 plants were resistant (≤100 aphids per plant) in the first screening test. All ‘Dowling’, PI 71506 and PI 230977 were resistant (≤150 aphids per plant), and 50% of plants of line ‘G93-9223’ were resistant in the second test. Follow-up experiments showed that antixenosis was a modality of resistance based on reduced nymphiposition by A. glycines on Dowling, PI 230977 and PI 71506 in no-choice tests and on fewer numbers of A. glycines on Dowling, PI 230977, PI 71506 and G93-5223 in distribution tests. Antixenosis in Dowling and PI 230977 was stronger in the unifoliolate leaves than in other shoot structures, whereas distribution of A. glycines within plants of PI 71506 and G93-5223 suggested comparable suitability between unifoliolate leaves and other shoot structures of these accessions. Antibiosis to A. glycines was evident as a lower proportion of aphids that reproduced on PI 230977 and from fewer progeny on PI 230977 and Dowling than on 91B91. The number of days from birth to reproduction by A. glycines did not differ among accessions. Results confirmed Dowling and PI 71506 as strong sources of resistance to A. glycines. The levels of antixenosis and antibiosis to A. glycines in PI 230977 and antixenosis to A. glycines in G93-9223 suggest that these accessions may also be valuable to soybean breeding programs as sources of resistance.

There is little information available that describes the effects of bird cherry-oat aphids (Rhopalosiphum padi L.) and Barley yellow dwarf virus (BYDV) on cereal plant root systems. This 2-yr field experiment was conducted to determine how spring wheat (Triticum aestivum L.) root characteristics, shoot characteristics, and grain yield respond to R. padi infestation, BYDV infection, or a combination of R. padi plus BYDV. Treatments were applied at the 2- to 3-leaf stage. When measured at anthesis, plants that received R. padi treatments (300 aphid days) had about a 30% greater total root length (as measured with a minirhizotron) than control plants. Plants that received BYDV as well as those that received R. padi plus BYDV had about a 40% decrease in total root length when compared with the control. Root system characteristics at different soil depths responded differently to BYDV infection across the 2 yr of the study. In the first year, BYDV-infected plants had less root length at all soil depths measured than plants that did not receive BYDV infection. In the second year, which was drier near anthesis, root lengths of both BYDV infected and uninfected plants were similar at the 0- to 18-cm soil depth, while at deeper soil depths, plants that had BYDV infection had less root length than plants that did not receive BYDV infection. Plants that received either R. padi or BYDV had fewer tillers, less tiller height, and less shoot dry weight than control plants. The lack of R. padi x BYDV interaction for above-ground variables suggests that shoots responded to BYDV in a similar manner regardless of whether or not they received R. padi treatment. Treatments consisting of R. padi infestation or BYDV infection reduced individual kernel weight by 8 or 22%, respectively. Infection with BYDV also caused a 53% reduction in the number of kernels per meter of row and a 62% reduction in total grain yield. We conclude that R. padi infestation caused acute injury to spring wheat plants while BYDV caused chronic injury. Most of the dependent variables measured in this experiment responded to BYDV in a similar manner regardless of whether or not the plants received R. padi treatment.

The form of nutrient solution nitrogen (NH4-N or NO3-N) provided to plants can have profound influence upon the severity of many crop diseases. It is not known if nutrient solution nitrogen form would affect wheat (Triticum aestivum L.) resistance to bird cherry-oat aphids (Rhopalosiphum padi L.). The objectives of our growth chamber experiments were to determine if the form of nitrogen provided in plant nutrient solutions affected aphid population growth parameters or the ability of wheat to withstand infestation. For aphid population growth experiments, winter wheat plants were watered with a complete nutrient solution containing NO3-N or NH4-N for 13 d prior to infestation with nymphs. The time period to adulthood and the number of progeny produced were recorded. For plant growth experiments, spring wheat plants were grown in sand culture using half-strength complete nutrient solution containing NO3-N or NH4-N. Approximately 100 apterous aphids were applied to half of the plants 7 d after germination. Plants were harvested for shoot and root fresh weight measurement 6 days after infestation. Aphid population growth (development time, number of aphids produced, and intrinsic rate of increase) were not significantly affected by nutrient solution N form treatments. Plants grown with NH4-N nutrient solutions had significantly less shoot fresh weight (0.181 g for NH4-N; 0.230 g for NO3-N). Aphid infestation also significantly reduced shoot fresh weight (0.149 g in infested; 0.262 g in control). There were no significant interactions between nutrient solution N form and aphid treatments for shoot fresh weight. Aphid treatment did not reduce root fresh weight in plants given NO3-N nutrient solution (aphid infested = 0.15 g; control = 0.15 g), but did in plants given NH4-N nutrient solution (aphid infested = 0.11 g; control = 0.17 g). Thus, while N form given to wheat plants had no effect on aphid population growth characteristics, plants given NH4-N nutrient solution showed less root growth than plants given the NO3-N nutrient solutions.

The soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is a major pest of soybean, Glycine max (L.). Merr., that significantly reduces yield in northern production areas of North America. Insecticides are widely used to control soybean aphid outbreaks, but efforts are underway to develop host plant resistance as an effective alternative management strategy. Here, previously identified resistant lines were evaluated in laboratory tests against field-collected populations of soybean aphid and in field-plot tests over 2 yr in South Dakota. Six lines previously identified with resistance to soybean aphid--Jackson, Dowling, K1639, Cobb, Palmetto and Sennari--were resistant in this study, but relatively high aphid counts on Tie-feng 8 in field plots contrasted with its previously reported resistance. Bhart-PI 165989 showed resistance in one of two laboratory tests, but it had relatively large aphid infestations in both years of field tests. Intermediate levels of soybean aphid occurred in field plots on lines previously shown to have strong (Sugao Zairai, PI 230977, and D75-10169) or moderate resistance to soybean aphid (G93-9223, Bragg, Braxton, and Tracy-M). Sugao Zairai also failed to have a significant proportion of resistant plants in two laboratory tests against aphids field-collected in 2008, but it was resistant in laboratory tests with aphids collected in 2002, 2005, and 2006. Overall, results showed that lines with Rag (i.e., Jackson) or Rag1 gene (i.e., Dowling) had low aphid numbers, whereas lines with Rag2 (i.e., Sugao Zairai, Sennari) had mixed results. Collectively, responses of soybean aphid populations in laboratory and field tests in 2008 resembled a virulence pattern reported previously for biotype 3 soybean aphids, but virulence in soybean aphid populations was variable and dynamic over years of the study. These results, coupled with previous reports of biotypes virulent to Rag1, suggest that deployment of lines with a single aphid-resistance gene is limited for soybean aphid management, and that deployment strategies relying on multiple resistance genes may be needed to effectively use plant resistance against soybean aphid.

Adults, eggs, first instars, and root-feeding larvae of the rice water weevil, Lissorhoptrus oryzophilus Kuschel, were experimentally confined to rice, Oryza sativa L., plants in flooded and drained fields during experiments conducted in 1989-1990. In both years, oviposition was significantly greater under flooded conditions (5.8-32 mean number of eggs per plant) than under drained conditions (0-1 mean number of eggs per plant). Scars from leaf-feeding by adults were more abundant on plants in flooded plots in both years. Lengths of feeding scars were greater on plants from the flooded plot in 1989, but scar lengths did not differ between treatments in 1990. In 1989, survival of eggs exposed to drained conditions for 7 d was greater than for eggs exposed to flooded conditions for the same period. Survival of weevil eggs in 1990 did not differ among flooded and drained treatments. In 1989, fewer larvae established on plants when drainage occurred 1 dafter transplanting than on plants that were transplanted at the same time but remained under flooded conditions. In 1990, water management, block, and the interaction (water management and block) influenced larval establishment. Survival of root-feeding larvae did not differ between flooded and drained treatments in 1989, whereas in 1990, survival declined with an increasing duration of drainage. Draining rice fields may be effective in controlling rice water weevil infestations, particularly when targeted against adults. However, earlyseason drainage conflicts with other management practices and appears to be more costly, and appropriate timing of this practice may be difficult to establish.

Infestations by SA can reduce the yield of soybeans and the efficacy of various biorational spray treatments need evaluation as alternatives to chemical insecticides for SA control. The efficacy of an entomopathogenic fungal formulation, MicroAC, against SA was compared to that of a distilled-water spray check and an untreated check. Two identical efficacy tests were conducted in growth chambers at the Northern Grain Insects Research Laboratory, Brookings, SD. Each test used a RCB design with 10 replications. In each test, 30 greenhouse-raised soybean plants, growing individually in separate pots, were infested in the late VE stage (unifoliate leaves fully expanded, first trifoliate leaves expanding) with five SA (adults or late third instars) on the underside of each unifoliate leaf (total of 10 SA per plant). The plants were placed in a growth chamber (16:8 L:D photoperiod; mean temperature and R.H. of 21.4 C and 45.9%, first test; 21.3 C and 73.9%, second test). Seven days after infestation, SA were counted on each plant. Sprays were then applied 20 cm from each plant using the wide-angle mist setting on the nozzle of a handpumped squirt bottle. Sprays were applied to run-off with eight squirts (about 9.2 ml) directed per plant, four with the nozzle horizontal and four with nozzle tip pointed downward at approximately 30-degrees. The number of spores contained in an 8-squirt volume of MicroAC was enumerated by direct observation of diluted product suspensions on a light microscope using phase contrast microscopy and a hemacytometer. Sporulation rate was measured as colonyforming units (CFU) in dilution-series cultures plated on Sabouraud dextrose agar with 2 % yeast extract under growth chamber conditions; CFU were counted after a 4-day incubation period when colonies were visible and separate. After spray application, clear 10-cm-diam × 40-cm-tall cylindrical acetate cages with 16-mesh screen tops were placed over each plant, and plants were returned to the growth chamber. At 10 days after treatment (DAT), (23 Jun, first test; 11 Jul, second test), plants were clipped at soil level, and SA were counted on each plant. For each test, SA counts were subjected to ANOVA and treatment means separated using Tukey’s HSD (P = 0.05). Post-spray SA counts were log (x + 1)-transformed before analysis.

Disease and Insect Resistance in Plants provides a rich overview of host plant resistance and its application to crop and pest systems. It emphasizes conventional approaches, but it also covers modern techniques in assessing plant resistance, including cell and tissue culture andmolecular genetics (mainly inChapter 7). The book has a strong conceptual base that presents an excellent review of classical theories of hostÐ parasite interaction, the gene-for-gene hypothesis, and vertical and horizontal resistance. Disease and Insect Resistance in Plants is also practical in its discussion of laboratory and Þeld methods for identifying and developing resistant crop plants and in its attention to evaluation and eventual deployment of resistant plants. Thebookdraws concepts and examples fromawide range of crops and pests, but it focuses on certain Þeld and vegetable crops, particularly rice, wheat, oat, potato, and tomato. Consequently, crop pests and pathogens such as brown planthopper, Hessian sy, greenbug, rusts, late blight, and powdery mildew often receive detailed discussion spanning several paragraphs or a few pages at a time. These examples recur frequently throughout the book. Treatment of other cropÐpest examples is brief, sometimes limited to a single sentence. Disease and Insect Resistance in Plants is one of a few textbooks that covers resistance to both diseases and invertebrate pests. Several chapters effectively blend discussion of disease and invertebrate examples, especially in relation to the value of resistance (Chapter 1), resistance sources and testing methods (Chapter 5), conventional breeding methods (Chapter 6), and the stability and vulnerability of resistance (Chapter 8). However, discussion of disease versus invertebrate resistance is unevenly partitioned in other parts of the book. Chapters 2 (disease concepts) and 4 (genetics of hostÐparasite interaction) collectively devote 126 pages to discussion of disease resistance in plants, whereas Chapter 3 allots roughly 45 pages to plant resistance against arthropods and compiles examples of resistance to nematodes 5 pages that make up Table 3.12. Chapter 7 (unconventional breeding methods) devotes 11 pages to plant pathogens, but only 2 pages to nematodes and 1 page to arthropods. In separating discussion of disease versus invertebrate resistance,Disease and Insect Resistance in Plants fails to link common threads of these subjects. For example, the gene-for-gene concept, originally developed to describe the relationship between virulence genes of fungal pathogens and disease-resistance genes in plants, has proven applicable in explaining interactions of host plants with other pathogens and with arthropod and nematode pests. The book could have pointed out that this concept applies to pathogen races and toarthropodbiotypes.Forexample,Chapter 3 covers plant resistance in relation to virulence of arthropod biotypes, and Chapter 4 covers the genefor-gene concept in the traditional manner with regard to virulence of plant pathogens. Unfortunately, the gene-for-gene concept is notmentioned explicitly in Chapter 3, except for a brief remark of studies that discount a “gene-for-gene relationship” between rice and the brown planthopper. Additionally, strict adherence tonarrowinterpretationsof thegene-for-geneconcept and its corollaries leave the reader with limited guidance on application of these principles to pathogens such as viroids or to plant defense systems based on structuralmodiÞcationssuchas leaf trichomes inrelation to arthropod resistance. The book also missed a clear opportunity to discuss plant pathogenÐvectorÐhost interactions in relation to resistance breeding, and the strategies of developing resistance to vectors versus the pathogens they transmit.More discussion and examples ofmanaging pathogenÐvector systems by host plant resistance (e.g., resistance in wheat to the wheat curl mite for limiting Wheat streak mosaic virus) would have enhanced the book. The abundant examples presented in Disease and Insect Resistance in Plants are supported by extensive references with a bibliography making up more than one sixth of the book. The authors fulÞll their objective to revise and enlarge their 1986 book entitled Breeding for Resistance to Diseases and Insect Pests by emphasizing newer and recent techniques and by citing 500 new references. Nevertheless, older references and examples are retained; thus, the book supplies both classic and modern examples of resistance topathogensandpests.Unfortunately, newreferences are not evenly distributed, but rather clustered among subject areas, as with Chapter 7Os 88 post-1986 references. Despite these updates, this chapter still cites some references from the 1970s or early 1980s as “recent” examples. Sometimes new references are compiled in lengthy tables rather than being integrated into text, e.g., Table 3.12 and especially Table 4.1, which spans 40 pages in updating the inheritance of resistance to pathogens in various plant species since 1990. Some chapters (e.g., Chapter 6) contain sections devoid of updated references. The book generally reads well, but editorial deÞciencies are apparent. The text contains many punctuation errors and misspellings. Intermittent use of oneor two-sentence paragraphs produces staccato text and a catalog-like list of examples of pathogen and invertebrate pests. Some lengthy paragraphs lack topic sentences, and there is occasionally poor transition between paragraphs. Sections and especially chapters have abrupt endings that lack bridging to material that follows. Text could have been tightened to improve readability. The font is small and straining to read. Many areas would have beneÞted from pictures, drawings, or other illustrations.

A RCBD with 5 replications was used to compare RWW larval control among 4 insecticide treatments and an untreated control. Rice plants were grown in a greenhouse in 1 liter plastic pots (10 cm diam) filled to 50% capacity with Stockton clay loam. Soil had been sifted through a 3.2-mm mesh screen and steam sterilized. Ammonium sulfate (0.5 g/pot) was added and lightly incorporated into the soil surface with forceps. Pots were flooded to a depth of 5 cm