Bean pod mottle virus: Spatial and temporal dynamics at different spatial scales and the impact of time of infection on soybean yield and quality

A comprehensive state-wide soybean disease survey was carried out during the 2005- 2007 growing seasons to determine seasonal and geospatial patterns of soybean diseases in Iowa. Bean pod mottle virus (BPMV) was one of the viruses assessed in the survey. To quantify BPMV prevalence and incidence at the field and county scales, 30 soybean plants per field were sampled from 8-20 soybean fields/county using a systematic sampling design. The GPS coordinates for each soybean field sampled were recorded. Soybean plants were tested for the presence of BPMV using enzyme linked immunosorbent assay (ELISA). Field- and county-scale BPMV prevalence and incidence data were mapped using ArcGIS (ESRI, Redlands, CA). County-scale prevalence of BPMV was 40.6% in 2005, 90.1% in 2006, and 74.7% in 2007. On the field basis, the prevalence of BPMV in soybean fields was 9.5%, 40.4% and 27.4% for 2005, 2006, and 2007, respectively. BPMV incidence within soybean fields from 2005-2007 was 4.4%, 24.8%, 9.8%, respectively. Moran\u27s I analysis revealed significant spatial dependence for BPMV incidence among counties, indicating a nonrandom distribution of BPMV among Iowa counties. Based on GIS point maps for the three growing seasons, kriged maps revealed an increased risk for BPMV from the southern border of the state to the northern border of the state. Regression analysis for relationship between BPMV incidence and county latitude indicated a strong linear relationship with BPMV incidence increasing from 0.24 to 2% for every 10 km increase in latitude during the 3-year study. To quantify the temporal and spatial spread of BPMV within soybean fields, 30-cm-long quadrats were established within field plots of the soybean cultivar NE3001 (150 quadrats per plot) in 2006 and 2007. Quadrats were sampled every 8-11 days throughout each growing season, beginning 25 days after planting. Sap from the youngest, fully-expanded leaflet from each of the four plants per quadrat was group tested for the presence of BPMV using ELISA. To determine the relationship between day of BPMV detection and soybean yield, 35 soybean quadrats representing each BPMV detection time were randomly selected to obtained yield, yield components, and grain quality data. For sampling dates with \u3c 35 quadrats that were BPMV positive, all quadrats were harvested to obtain yield data. Yield, yield components, and grain quality data from quadrats were then plotted with respect to day of year that BPMV was first detected in a quadrat, and linear regression was used to quantify the relationships between time of BPMV detection with yield, yield components (number of pods per plant, seeds per pod, and 100-seed weight), and grain quality (percent mottled seed, protein content and oil content) (y). BPMV was first detected in quadrats as early as the first sampling date (30 May 2006 and 12 June in 2007). The onset of BPMV epidemic (5% BPMV incidence) occurred on 29 June 2006 and on 18 July in 2007. Time to 50% BPMV incidence ranged from day of year 207 (26 July) to 215 (3 August) in 2006. In 2007 time to 50% occurred well past senescence. Final BPMV incidence was between 85.8 and 94.4% in 2006 and between 10.0 and 37.1% in 2007. In 2006, temporal rates of BPMV infection ranged from 0.09 to 0.12 logits/day with R2 values ranging from 97.8% to 98.3%, indicating that BPMV incidence within soybean plots doubled every 5.3 to 6.9 days. Rates of BPMV temporal spread in 2007 were significantly slower (0.05 to 0.07 logits/day, R2 values ranged from 91.6% to 99.7%), with doubling times ranging from 13.8 to 17.3 days. Plots with the earliest onset of BPMV had the highest BPMV incidence at the end of the growing season and the largest areas under the BPMV progress curves in both 2006 and 2007 (the slope for both years was 1.1 and R2 values of 65.4% and 76.9%, respectively). Spatial analyzes using ordinary runs revealed that BPMV-infected quadrats had spatial patterns that were highly aggregated throughout both growing seasons. Time of BPMV detection explained 89.7% and 57.9% of the variation in soybean yield in 2006 and 2007, respectively. The yield damage function (slope) was -0.23 bushels/acre/day in 2006 and -0.12 bushels/acre/day, indicating that for every 4.3 and 8.3 days BPMV detection was delayed, in 2006 and 2007, respectively, soybean yield would increase by one bushel. The linear relationship between number of pods per plant and time of BPMV detection was significant in 2006 (slope = 0.15, R2 = 72.8%), but not in 2007. The number of seeds per pod was not impacted by time of BPMV detection in either year, and 100-seed weight was impacted only in 2006 (slope = 0.013, R2 = 78.5%). There was a significant linear relationship between time of BPMV detection and the percentage of mottled seeds in the two years (slope = 0.34, 0.15; R2 = 82.8, 48.3%); earlier BPMV detection was associated with a higher percentage of mottled seeds. Time of BPMV detection in a quadrat did not influence protein and oil content in either year. This research was the first to document the nonrandom distribution of BPMV prevalence and incidence in Iowa, and the first to show that BPMV spread within soybean fields is highly aggregated over time, which has important implications for yield losses and BPMV sampling designs. This project was also the first to quantify the relationship between BPMV date of detection and reduction in yield and impact on yield components and soybean quality

Reproduction of Soybean Cyst Nematode Populations on Field Pennycress, Henbit, and Purple Deadnettle Weed Hosts

Several weeds serve as alternative soybean cyst nematode (SCN) hosts. Still, the relative reproductive capacity of SCN HG types (Heterodera glycines type) on weed hosts relative to soybean is not well understood. This study examined the reproduction of three South Dakota endemic SCN populations—PSCN-1 (HG 0), PSCN-2 (HG 2.5.7), and PSCN-3 (HG 7)—on purple deadnettle, field pennycress, and henbit. The Relative Female Index (RFI) was calculated to compare SCN reproduction relative to the susceptible soybean check. Weed hosts, HG types, and their interactions influenced SCN reproduction. Henbit (RFI = 51.8) and purple deadnettle (RFI = 47.6) roots had a similar high RFI, whereas field pennycress (RFI = 23.04) had a lower RFI. Similarly, SCN populations PSCN-1 and PSCN-3 had a similar RFI of 36.9 and 37.2, respectively, while the population PSCN-2 had a higher RFI of 44.9 across weed hosts. A significant interaction between PSCN-1 and purple deadnettle was observed where the RFI was the highest (RFI = 53.3). These results indicate that these weed hosts support endemic SCN populations, and the HG type influenced reproductive success, further complicating SCN management. Hence, SCN presents a significant challenge in the new prospect of incorporating field pennycress host as an oilseed cover crop in the Midwest’s corn–soybean production system

Bean Pod Mottle Virus Prediction Map Updated

The figure below has been updated in Predicted Risk of Bean Pod Mottle Virus in 2010 - an article first posted April 12. The original map had incomplete data for some counties. Data for those counties are now available and are reflected in the the map below. See complete article

Impact of Soybean Row Spacing on Bean Pod Mottle Virus

Bean pod mottle virus (BPMV) remains the most prevalent viral disease of soybean in the U.S., affecting both soybean yield and quality. This plant virus is spread primarily by bean leaf beetles. The objective of this study was to quantify the temporal and spatial spread of BPMV in three different soybean row spacings (7.5 in., 15 in., and 30 in.)

Impact of Bean Pod Mottle Virus on Soybean Yield and Quality in Iowa

Bean pod mottle virus (BPMV) was the second most prevalent disease of soybean in Iowa (Iowa Soybean Disease Survey 2005 through 2007). The principal means of BPMV spread is by insect vectors, with the bean leaf beetle (Cerotoma trifucarta Forster) being the most important and abundant vector. This virus also can be seedborne, resulting in seed-to-seedling transmission, with BPMVinfected seedlings serving as a source of virus infection within the soybean crop. Although the first report of BPMV in the North Central United States originally occurred in Iowa, the impact of BPMV on soybean yield and quality had not been well documented. This project focused on quantifying the effect of time of BPMV detection (related to time of infection) on soybean yield and grain quality

Soybean Mosaic Virus and Bean Pod Mottle Virus in Iowa: Occurrence, Interactions, Impact and Identification of Preplant Risk Factors

This presentation will summarize data collected from the Iowa Soybean Disease Survey on the temporal and spatial distribution of soybean mosaic virus (SMV) and bean pod mottle virus (BPMV) in Iowa during the 2005 and 2006 growing seasons. We will also discuss interactions of the viruses with each other, their vectors, Phomposis/Diaporthe complex. Lastly, the identification of preplant risk factors for BPMV will be presented

Assessing Integrated Pest Management Implementation and Knowledge Gaps in South Dakota

A survey of commercial pesticide applicator training participants was carried out during 2015 winter pesticide certification meetings to assess integrated pest management (IPM) knowledge gaps. Overall, the majority of the respondents reported that they have adequate access to IPM information and that they apply IPM principles in their pest management programs. Preventive fungicide use was identified as a regular practice by half the respondents and was dependent on the region of the state. Participants identified basic pest identification as an area in which more resources are needed. Online information and field days were the preferred options for accessing outreach and Extension

Predicted Risk of Bean Pod Mottle Virus in 2010

Bean pod mottle virus (BPMV) continues to pose a threat to soybean production by reducing soybean yield and affecting soybean quality. In a recent 3-year survey study conducted during the 2005 through 2007 soybean growing seasons, BPMV was found to be one of the most prevalent soybean diseases in Iowa, with BPMV being detected in 10 (2005) to 40 percent (2006) of the approximately 1,200 soybean fields sampled and tested each growing season. By mapping BPMV incidence at the county scale, BPMV incidence (risk) was found to occur at varying intensities within and among Iowa counties. Generally, risk of BPMV tended to decrease in a gradient from south to north within county tiers (Figure 1)

Winter Wheat Grain Yield Response to Fungicide Application is Influenced by Cultivar and Rainfall

Winter wheat is susceptible to several fungal pathogens throughout the growing season and foliar fungicide application is one of the strategies used in the management of fungal diseases in winter wheat. However, for fungicides to be profitable, weather conditions conducive to fungal disease development should be present. To determine if winter wheat yield response to fungicide application at the flowering growth stage (Feekes 10.5.1) was related to the growing season precipitation, grain yield from fungicide treated plots was compared to non-treated plots for 19 to 30 hard red winter wheat cultivars planted at 8 site years from 2011 through 2015. At all locations, Prothioconazole + Tebuconazole or Tebuconazole alone was applied at flowering timing for the fungicide treated plots. Grain yield response (difference between treated and non-treated) ranged from 66-696 kg/ha across years and locations. Grain yield response had a positive and significant linear relationship with cumulative rainfall in May through June for the mid and top grain yield ranked cultivars (R2=54%, 78%, respectively) indicating that a higher amount of accumulated rainfall in this period increased chances of getting a higher yield response from fungicide application. Cultivars treated with a fungicide had slightly higher protein content (up to 0.5%) compared to non-treated. These results indicate that application of fungicides when there is sufficient moisture in May and June may increase chances of profitability from fungicide application

Meta-analysis of yield response of foliar fungicide-treated hybrid corn in the United States and Ontario, Canada

Foliar fungicide applications to corn (Zea mays L.) occur at one or more application timings ranging from early vegetative growth stages to mid-reproductive stages. Previous studies indicated that fungicide applications are profitable under high disease pressure when applied during the tasseling to silking growth stages. Few comprehensive studies in corn have examined the impact of fungicide applications at an early vegetative growth stage (V6) compared to late application timings (VT) for yield response and return on fungicide investment (ROI) across multiple locations