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The aphid Aphis glycines Matsumura, which was first observed in North America in 2000, is a pest of soybean, Glycine max L., in the United States and southern Canada. This study focused on the distribution and sampling of this aphid at two spatial scales: field and township. We sampled 14 soybean fields in each of two townships in Kendall and Champ...

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Soybean aphid, Aphis glycines (Hemiptera: Aphididae), is the most economically important soybean [Glycine max (L.) Merr.] pest of North America. Multiple studies have identified soybean expressing antibiosis and/or antixenosis; however, soybean tolerance remains underexplored. Tolerance to soybean aphid injury was previously identified in soybean K...

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... Soybean aphid infestations can be effectively managed with threshold-based (i.e., 250 aphids per plant) sprays of foliar insecticides to prevent populations from reaching the economic injury level (EIL; i.e., 5,563 cumulative aphid-days; Ragsdale et al. 2007, Johnson et al. 2009). Sampling plans have been developed to estimate soybean aphid densities and facilitate pest management decision making (Hodgson et al. 2004Onstad et al. 2005). Song and Swinton (2009) predicted that the use of integrated pest management (IPM) for soybean aphid can generate a net economic benefit of US$1.3 billion over 15 years. ...
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Soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is the most economically important insect pest of soybean in the north central United States. Scouting-based integrated pest management (IPM) programs could become more efficient and more widely adopted by using plant spectral reflectance to estimate soybean aphid injury. Our objective was to determine whether plant spectral reflectance is affected by soybean aphid feeding. Field trials were conducted in 2013 and 2014 using caged plots. Early-, late-, and noninfested treatments were established to create a gradient of soybean aphid pressure. Whole-plant soybean aphid densities were recorded weekly. Measurements of plant spectral reflectance occurred on two sample dates per year. Simple linear regression models were used to test the effect of cumulative aphid-days (CAD) on plant spectral reflectance at 680 nm (RED) and 800nm (NIR), normalized difference vegetation index (NDVI), and relative chlorophyll content. Data indicated that CAD had no effect on canopy-level RED reflectance, but CAD decreased canopy level NIR reflectance and NDVI. Canopy- and leaf-level measurements typically indicated similar plant spectral response to increasing CAD. CAD generally had no effect on relative chlorophyll content. The present study provides the first documentation that remote sensing holds potential for detecting changes in plant spectral reflectance induced by soybean aphid. The use of plant spectral reflectance in soybean aphid management may assist future IPM programs to reduce sampling costs and prevent prophylactic insecticide sprays.
... Soybean aphid infestations can be effectively managed with threshold-based (i.e., 250 aphids per plant) sprays of foliar insecticides to prevent populations from reaching the economic injury level (EIL; i.e., 5,563 cumulative aphid-days; Ragsdale et al. 2007, Johnson et al. 2009). Sampling plans have been developed to estimate soybean aphid densities and facilitate pest management decision making (Hodgson et al. 2004Onstad et al. 2005). Song and Swinton (2009) predicted that the use of integrated pest management (IPM) for soybean aphid can generate a net economic benefit of US$1.3 billion over 15 years. ...
Conference Paper
Soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is an economically important insect pest of soybean throughout the North Central United States. In-field scouting is critical to predict and maintain aphid densities below the economic injury level of ≈670 aphids/plant. Detection of insect feeding by measuring pest-induced changes in the proportion of incident light reflected by plant leaves (i.e., reflectance) holds promise for precise scouting programs. Our objective was to identify potential spectral bandwidths for detecting aphid-induced stress. Field trials were conducted in 2013 and 2014 using caged-plots (1-m width × 1-m length) arranged in a randomized complete block design with 7-8 replications. Three treatments (i.e., early infested, late infested, and aphid-free) were established to create differential soybean aphid populations. Four independent trials were also conducted under greenhouse conditions. Aphid densities were converted to cumulative aphid-days to be regressed against vegetation indices and spectral bandwidths recorded between 350 nm and 2500 nm. Cumulative aphid-days had a strong negative relationship with bandwidths in the near-infrared spectral range (i.e., 770-880 nm). Significant increase on the reflectance of some visible wavelengths (i.e., 400-700 nm) evidenced a reduction in chlorophyll content due to aphid feeding. Furthermore, our results suggested that narrow wavelengths can be satisfactorily combined in vegetation indices to predict aphid densities before economic losses. Decisions for soybean aphid control based on aphid-induced spectral changes may reduce the cost of sampling procedures, and perhaps make scouting more efficient and feasible to farms.
... Organisms, including insects, differ in their responses to field edges. For some, population densities can be higher on the edges than in the center but, for others, it can be lower or similar (31,32,37,38). ...
... One of the common themes among the findings in these studies is that organisms respond differentially to habitat edges (38). For example, some insect species respond positively (9,31,34,46) or negatively (9,10,14,31) while others are neutral (9,30,32). ...
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Zebra chip is a newly emerging potato disease which imparts dark colorations on fried chips, rendering them unmarketable. The disease is associated with the phloem-limited proteobacterium 'Candidatus Liberibacter solancearum', vectored by the potato psyllid Bactericem cockerelli. First reported from Mexico in the mid-1990s, the disease was observed for the First time in Texas in 2000 and is now prevalent in several potato-producing regions of the United States. In this study, we were interested in investigating whether there are edge effects in zebra chip intensity that can be assessed as a "foot print" of the associated insect vector. In 2009, we conducted studies in three fields in the Texas Panhandle in paired plots of 10 by 20 m around the field edges and 100 m infield in which symptomatic plants were counted just before harvest. The number of plot pairs (edge and infield) ranged from 15 to 18 depending on the size of the fields. In a separate study, temporal disease progress was assessed in two fields around the edges of the center-pivot circle in approximately 10-by-450-m areas. In 2010, the paired plot studies were repeated in 10 potato fields in Texas, Kansas, and Nebraska. Zebra chip intensity data from the paired-plot studies for both years were analyzed using the Wilcoxon's signed-rank test, a nonparametric equivalent of the classical (parametric) paired t test. In the 2009 study in all three fields, the edge plots had significantly greater zebra chip intensity than, the infield plots (P < 0.05). Edge plots in the 2010 study also had greater zebra chip intensity in all fields and the differences were significant in the majority of fields (P < 0.05). In the diseases progress study in both fields, weekly zebra chip intensity on the edges reached its maximum after the third week of its first detection, and the disease progress curves were best fitted with the second-degree polynomial (quadratic) for both fields. The 2-year study clearly demonstrated that zebra chip intensity in potato fields was greater on the edges than in the infields. This finding has significant implications for psyllid management because greater emphasis in psyllid control strategy can be directed toward the edges for better results.
... Organisms, including insects, differ in their responses to field edges. For some, population densities can be higher on the edges than in the center but, for others, it can be lower or similar (31,32,37,38). ...
... One of the common themes among the findings in these studies is that organisms respond differentially to habitat edges (38). For example, some insect species respond positively (9,31,34,46) or negatively (9,10,14,31) while others are neutral (9,30,32). ...
... In addition, there is temporal asynchrony in the colonization of soybean by soybean cyst nematode and soybean aphid during the growing season. Soybean cyst nematode occurs in the soil and infects soybean roots shortly after germination (Niblack et al. 2006), while soybean aphid colonizes plants in the mid-late summer after plants have established a canopy (Ragsdale et al. 2004, Onstad et al. 2005). This scenario may create the opportunity for the early colonizing soybean cyst nematode to inßuence the performance and/or preference of laterarriving soybean aphid indirectly via herbivore-induced responses in the shared host plant. ...
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Herbivores on plants frequently interact via shared resources. Studies that have examined performance of herbivores in the presence of other herbivores, however, have often focused on above-ground feeding guilds and relatively less research has examined interactions between below- and above-ground consumers. We examine how soybean aphid, Aphis glycines (Matsumura) an above-ground phloem-feeding herbivore, interacts with a below-ground plant parasite, soybean cyst nematode, Heterodera glycines (Ichinohe) through their shared host plant, soybean (Glycine max L). Laboratory experiments evaluated the preference of alate (flight-capable) soybean aphids toward plants either infected with soybean cyst nematode or uninfected controls in a simple choice arena. Alate soybean aphids preferred uninfected soybean over soybean cyst nematode-infected plants: 48 h after the releases of alate aphids in the center of the arena, 67% more aphids were found on control soybean compared with nematode infected plants. No-choice feeding assays were also conducted using clip cages and apterous (flight-incapable) aphids to investigate effect of soybean cyst nematode infection of soybean on aphid performance. These studies had mixed results: in one set of experiments overall aphid population growth at 7 d was not statistically different between control and soybean cyst nematode-infected plants. A different experiment using a life-table analysis found that apterous aphids feeding on soybean cyst nematode-infected plants had significantly greater finite rate of increase (λ), intrinsic rate of increase (r(m)), and net reproductive rate (R(o)) compared with aphids reared on uninfected (control) soybean plants. We conclude that the below-ground herbivore, soybean cyst nematode, primarily influences soybean aphid behavior rather than performance.
... Recently, Ragsdale et al. (2007) developed an economic injury level and an economic threshold for soybean aphid that is based on the number of aphids per plant in open Þeld plots. Similarly, available sampling plans for soybean aphid are based on whole-plant counts as their sample unit (Hodgson et al. 2004, Onstad et al. 2005. However, estimating whole-plant aphid densities is a time consuming process, especially with high aphid infestation (Mc-Cornack et al. 2008). ...
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The soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), is currently the most important insect threat to soybean, Clycine max (L.) Merr., production in the North Central United States. Field cage studies are a key tool in investigating the potential of natural enemies and host plant resistance to control this pest. However, a major constraint in the use of cage studies is the limited number of treatments and replicates that can be used as aphid densities frequently become so large as to limit the number of experimental units that can be quantified. One way to overcome this limitation is to develop methods that estimate whole-plant aphid densities based on a reduced sampling plan. Here, we extend an existing method, node-sampling, used for estimating aphid populations in open field conditions and apply it to caged populations. We show that parameters calculated under open field conditions are inappropriate to estimate caged populations. In contrast, using four independent data sets of caged populations and a cross-validation technique, we demonstrate that a three-node sampling unit and a weighted formula provide accurate and robust estimates of whole-plant aphid density. This method reduced the number of aphids counted per plant by and average of 60%, with greater reductions at higher aphid densities. We further demonstrate that nearly identical statistical results were obtained when whole-plant or node-sampling estimates were used in the analysis of two case studies. The reduced sample unit method developed here saves time without sacrificing efficiency so that more plants, replications, or studies can be conducted that will lead to improved soybean aphid management.
... A. glycines is a heteroecious aphid that feeds on soybean in the summer and migrates to its primary host (buck-thorn [Rhamnus sp.]) in the fall. Obtaining reliable estimates of aphid density in individual Þelds is laborious due to the large variation in abundance among Þelds over small spatial scales (Onstad et al. 2005). The current study investigated the potential of using suction trap samples to forecast the abundance of A. glycines in soybean Þelds at the county level. ...
... Relationship between the cumulative abundance of A. glycines sampled in soybean Þelds or captured in suction traps before 1 September. and on soybean plants among years (Fig. 2) and 2) the high level of variation in aphid abundance among soybean Þelds within a county ( Fig. 3; also see Onstad et al. 2005). Captures of winged A. glycines in suction traps probably reßects migration events for local populations as well as colonization by long-distance migrants, which may explain the lack of congruence for the trends observed in suction traps and soybean plants at the county level. ...
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The current study evaluated the potential of using counts of winged adults captured in suction traps to forecast the local abundance of soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae), in soybean, Glycine max (L.) Merr., fields. The abundance of aphids was evaluated weekly by sampling plants in four to 11 soybean fields and recording the number of aphids in suction traps between 2006 and 2008 in four counties in Indiana and Illinois. Fields in each county were located within 10 km of their respective suction trap, which allowed us to evaluate the relation between aphid abundance on soybean plants and in suction traps at the county level. Migrant soybean aphids caught in suction traps exhibited distinct seasonal trends each year: in 2006, trapped migrants consisted predominantly of individuals dispersing from soybean to buckthorn (Rhamnus sp.); in 2007, in contrast, the majority of trapped migrants were apparently individuals dispersing among soybean fields. The cumulative number of aphids captured in suction traps was positively related to aphid densities on soybean plants. However, the utility of suction traps as a monitoring tool may be limited by the variation in temporal patterns observed in suction traps and on soybean plants each year, and the spatial variation in aphid abundance among soybean fields within a county.
... Several sampling methods have been described in recent years in the North Central United States . These include whole plant counts , enumerative sampling , binomial sampling , and rating scales . Onstad et al . ( 2005 ) determined that whole plant counts of 50 plants per field , within 50 m from the field edge , should be completed for the most reliable estimate of the population . However , they found this to be very time consuming at high soybean aphid densities and when the canopy was closed . ...
... Rhamnus cathartica (common buckthorn) was a confirmed overwintering host in 2000 (DiFonzo 2001). R. canthartica, R. alnifolia (Voegtlin et al. 2004) and R. lanceolata (Voegtlin et al. 2005) were found to be overwintering hosts of A. glycines. ...
... Stylet penetration by aphids is indispensable in host plant acceptance and rejection (Prado and Tjallingii 1997); in fact, every species of aphid we have tested, using the electrical penetration graph (EPG) technique (Fig. 10), will initiate probing on every species of non-host plant they have been offered (unpublished data). Since A. glycines appeared in North America, several studies on this insect have been done in diverse areas which include chemical control (), biological control (), plant viruses (), ecology (, Voegtlin et al. 2005), and plant resistance () among others. The only study reporting the use of the EPG technique for observing A. glycines feeding behavior was conducted in China by Han and Yan (1995) where stylet activities on host (soybean) and nonhost plants (cotton, Gossypium hirsutum; cucumber, Cucumis sativa; and loofah, Luffa cylindrical) were examined. ...
Thesis
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The soybean aphid, Aphis glycines Matsumura, is a pest of soybean, Glycine max (L.) Merr. Studies to find control methods were initiated in 2000 when it was first detected in the United States. Aphis glycines can reduce yields by as much as 50%, and vectors several viral diseases. Plant resistance to A. glycines is one important component of integrated control. In the first study, reproduction of A. glycines was compared on 240 soybean entries. Eleven had fewer nymphs produced compared with two susceptible checks (KS4202 and Pioneer® 95B15). Antibiosis and antixenosis were assessed in no-choice and choice tests, respectively. Nine entries showed moderate antibiosis and the other two (K1639 and Pioneer® 95B97) showed strong antibiosis and antixenosis as categories of resistance to A. glycines. In the second study, chlorophyll loss was estimated in no-choice tests on infested and uninfested leaves of KS4202. The minimum combined number to detect significant chlorophyll loss was 30 aphids confined for 10 days. Using this number, seven resistant entries found in the first study were evaluated. There was no significant chlorophyll reduction between infested and uninfested leaves of five of the resistant entries (K1621, K1639, 95B97, Dowling and Jackson). Jackson and Dowling had a significantly lower percentage loss than the susceptible checks. In the third study, assessment of feeding behavior of A. glycines was compared and recorded for 9 h on four resistant entries and KS4202. The average time needed to reach the first sieve element phase by A. glycines was 3.5 h in KS4202 while in the resistant entries it was 7.5 h, and the total duration in this phase was longer than an hour in KS4202, and only two to seven minutes in the resistant entries. These data suggest that phloem tissues in the resistant plants change feeding behavior. However, aphids first reached the xylem phase and then the sieve element phase, and the time that aphids spent ingesting xylem sap was not different among all entries; therefore, it is possible that xylem sap in the resistant entries may contain toxic substances that alter aphid behavior and restrain further activities on the sieve element phase.
... However, during the 2002 and 2004 growing seasons, aphid population levels were relatively low, with few if any yield losses reported from soybean producers (Ragsdale et al. 2004). In addition, aphid densities also varied considerably among production Þelds within growing seasons (Onstad et al. 2005). Currently, little is known regarding the factors that regulate soybean aphid populations and contribute to population outbreaks . ...
Article
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Soybean aphid populations have been hypothesized to respond to nutrient availability in soybean plants. We examined how soil potassium (K) deficiency affects soybean aphid population at both regional and field level scales. First, we measured soil and leaf nutrient levels and monitored soybean aphid populations in 34 production soybean fields throughout Wisconsin. A principle component analysis (PCA) was used to examine the relationship between soil and leaf nutrients and soybean aphid population growth. Results showed that aphid population growth rate was negatively correlated with soil K and P and leaf K, N, P, and S, whereas peak aphid densities were positively correlated with the same suite of soil and leaf nutrients. In a manipulative field experiment, we established low, medium, and high K fertility soybean plots and determined life table parameters of soybean aphids. Aphids developing within clip-cages showed a significantly greater intrinsic rate of population increase and net reproductive rate in the low K treatments in comparison with the medium and high K treatments. In these same plots, naturally colonizing populations of soybean aphids also had significantly higher peak abundance and rate of population increase in the low K treatment compared with medium and high K treatments. In general, these findings indicate that soil K availability and leaf K levels affect plant quality and may play an important role in soybean aphid population dynamics.