Integrated Management of Alfalfa Diseases

Alfalfa diseases can reduce forage quality and the longevity of alfalfa stands. Integrated management of diseases can minimize disease impact and improve forage stand and quality. There are several important pathogens that cause disease on alfalfa, and the occurrence of these diseases, as well as the severity of damage, depend on several factors, including the type of pathogen, the environment, and the level of resistance of the host to a particular disease. In addition, disease presence and severity are also influenced by agronomic practices, particularly sowing dates, cutting dates and frequency, and fertility programs

Integrated Management of Alfalfa Diseases

Alfalfa diseases can reduce forage quality and the longevity of alfalfa stands. Integrated management of diseases can minimize disease impact and improve forage stand and quality. There are several important pathogens that cause disease on alfalfa, and the occurrence of these diseases, as well as the severity of damage, depend on several factors, including the type of pathogen, the environment, and the level of resistance of the host to a particular disease. In addition, disease presence and severity are also influenced by agronomic practices, particularly sowing dates, cutting dates and frequency, and fertility programs

Preparing Youths for Careers in Agriculture Through State Crop Scouting Competitions

State crop scouting competitions (CSCs) promote agriculture by introducing youths in Indiana, Iowa, and Nebraska to various agricultural disciplines while focusing on integrated pest management (IPM). High school students compete as teams to address crop management issues at various stations. Each station is led by university representatives. Two surveys were conducted to determine the impacts of the competition on students. Results indicate that students improved in skills key to future careers and that they learned about aspects of IPM. CSCs can serve as models for states that wish to improve ties between university-based Extension specialists and state high schools

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

Background 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. Objective Compare yield response of fungicide application timing across multiple fungicide classes and calculate the probability of positive ROI. Methods Data were collected specifically for this analysis using a uniform protocol conducted in 13 states in the United States and one province in Canada from 2014–2015. Data were subjected to a primary mixed-model analysis of variance. Subsequent univariate meta-analyses, with and without moderator variables, were performed using standard meta-analytic procedures. Follow-up power and prediction analyses were performed to aid interpretation and development of management recommendations. Results Fungicide application resulted in a range of yield responses from -2,683.0 to 3,230.9 kg/ha relative to the non-treated control, with 68.2% of these responses being positive. Evidence suggests that all three moderator variables tested (application timing, fungicide class, and disease base level), had some effect (α = 0.05) on the absolute difference in yield between fungicide treated and non-treated plots (). Application timing influenced , with V6 + VT and the VT application timings resulting in greater yield responses than the V6 application timing alone. Fungicide formulations that combined demethylation inhibitor and quinone outside inhibitor fungicides significantly increased yield response. Conclusion Foliar fungicide applications can increase corn grain yield. To ensure the likelihood of a positive ROI, farmers should focus on applications at VT and use fungicides that include a mix of demethylation inhibitor and quinone outside inhibitor active ingredients

Ecology and diversity of culturable fungal species associated with soybean seedling diseases in the Midwestern United States

Aims: To isolate and characterize fungi associated with diseased soybean seedlings in Midwestern soybean production fields and to determine the influence of environmental and edaphic factors on their incidence. Methods and Results: Seedlings were collected from fields with seedling disease history in 2012 and 2013 for fungal isolation. Environmental and edaphic data associated with each field was collected. 3036 fungal isolates were obtained and assigned to 76 species. The most abundant genera recovered were Fusarium (73%) and Trichoderma (11.2%). Other genera included Mortierella, Clonostachys, Rhizoctonia, Alternaria, Mucor, Phoma, Macrophomina and Phomopsis. Most recovered species are known soybean pathogens. However, non-pathogenic organisms were also isolated. Crop history, soil density, water source, precipitation and temperature were the main factors influencing the abundance of fungal species. Conclusion: Key fungal species associated with soybean seedling diseases occurring in several US production regions were characterized. This work also identified major environment and edaphic factors affecting the abundance and occurrence of these species. Significance and Impact of the Study: The identification and characterization of the main pathogens associated with seedling diseases across major soybean-producing areas could help manage those pathogens, and devise more effective and sustainable practices to reduce the damage they cause

Defining optimal soybean seeding rates and associated risk across North America

Soybean [Glycine max (L.) Merr.] seeding rate research across North America is typically conducted in small geo-political regions where environmental effects on the seeding rate × yield relationship are minimized. Data from 211 individual field studies (∼21,000 data points, 2007–2017) were combined from across North America ranging in yield from 1,000– 7,500 kg ha−1. Cluster analysis was used to stratify each individual field study into similar environmental (soil × climate) clusters and into high (HYL), medium (MYL), and low (LYL) yield levels. Agronomically optimal seeding rates (AOSR) were calculated and Monte Carlo risk analysis was implemented. Within the two northern most clusters the AOSR was higher in the LYL followed by the MYL and then HYL. Within the farthest south cluster, a relatively small (±15,000 seeds ha−1) change in seeding rate from the MYL was required to reach the AOSR of the LYL and HYL, respectively. The increase in seeding rate to reach the LYL AOSR was relatively greater (5x) than the decrease to reach the HYL AOSR within the northern most cluster. Regardless, seeding rates below the AOSR presented substantial risk and potential yield loss, while seeding rates above provided slight risk reduction and yield increases. Specific to LYLs and MYLs, establishing and maintaining an adequate plant stand until harvest maximized yield regardless of the seeding rate, while maximizing seed number was important with lower seeding rates. These findings will help growers manage their soybean seed investment by adjusting seeding rates based upon the productivity of the environment.Fil: Gaspar, Adam P.. Dow Agrosciences Argentina Sociedad de Responsabilidad Limitada.; ArgentinaFil: Mourtzinis, Spyridon. University of Wisconsin; Estados UnidosFil: Kyle, Don. Dow Agrosciences Argentina Sociedad de Responsabilidad Limitada.; ArgentinaFil: Galdi, Eric. Dow Agrosciences Argentina Sociedad de Responsabilidad Limitada.; ArgentinaFil: Lindsey, Laura E.. Ohio State University; Estados UnidosFil: Hamman, William P.. Ohio State University; Estados UnidosFil: Matcham, Emma G. University of Wisconsin; Estados UnidosFil: Kandel, Hans J.. North Dakota State University; Estados UnidosFil: Schmitz, Peder. North Dakota State University; Estados UnidosFil: Stanley, Jordan D.. North Dakota State University; Estados UnidosFil: Schmidt, John P.. Dow Agrosciences Argentina Sociedad de Responsabilidad Limitada.; ArgentinaFil: Mueller, Daren S.. University of Iowa; Estados UnidosFil: Nafziger, Emerson D.. University of Illinois; Estados UnidosFil: Ross, Jeremy. University of Arkansas for Medical Sciences; Estados UnidosFil: Carter, Paul R.. Dow Agrosciences Argentina Sociedad de Responsabilidad Limitada.; ArgentinaFil: Varenhorst, Adam J.. University of South Dakota; Estados UnidosFil: Wise, Kiersten A.. University of Kentucky; Estados UnidosFil: Ciampitti, Ignacio Antonio. Kansas State University; Estados UnidosFil: Carciochi, Walter Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; Argentina. Kansas State University; Estados UnidosFil: Chilvers, Martin I.. Michigan State University; Estados UnidosFil: Hauswedell, Brady. University of South Dakota; Estados UnidosFil: Tenuta, Albert U.. University of Guelph; CanadáFil: Conley, Shawn P.. University of Wisconsin; Estados Unido

Population genomic analysis reveals geographic structure and climatic diversification for Macrophomina phaseolina isolated from soybean and dry bean across the United States, Puerto Rico, and Colombia

Macrophomina phaseolina causes charcoal rot, which can significantly reduce yield and seed quality of soybean and dry bean resulting from primarily environmental stressors. Although charcoal rot has been recognized as a warm climate-driven disease of increasing concern under global climate change, knowledge regarding population genetics and climatic variables contributing to the genetic diversity of M. phaseolina is limited. This study conducted genome sequencing for 95 M. phaseolina isolates from soybean and dry bean across the continental United States, Puerto Rico, and Colombia. Inference on the population structure using 76,981 single nucleotide polymorphisms (SNPs) revealed that the isolates exhibited a discrete genetic clustering at the continental level and a continuous genetic differentiation regionally. A majority of isolates from the United States (96%) grouped in a clade with a predominantly clonal genetic structure, while 88% of Puerto Rican and Colombian isolates from dry bean were assigned to a separate clade with higher genetic diversity. A redundancy analysis (RDA) was used to estimate the contributions of climate and spatial structure to genomic variation (11,421 unlinked SNPs). Climate significantly contributed to genomic variation at a continental level with temperature seasonality explaining the most variation while precipitation of warmest quarter explaining the most when spatial structure was accounted for. The loci significantly associated with multivariate climate were found closely to the genes related to fungal stress responses, including transmembrane transport, glycoside hydrolase activity and a heat-shock protein, which may mediate climatic adaptation for M. phaseolina. On the contrary, limited genome-wide differentiation among populations by hosts was observed. These findings highlight the importance of population genetics and identify candidate genes of M. phaseolina that can be used to elucidate the molecular mechanisms that underly climatic adaptation to the changing climate

Proceedings of the 50th Annual Meeting, Southern Soybean Disease Workers (March 1-2, 2023, Pensacola Beach, Florida)

Southern United States Soybean Disease Loss Estimates for 2022. TW Allen, K Bissonnette, CA, Bradley, TR Faske, Z Grabau, T Isakeit, RC Kemerait, A Koehler, D Langston, J Lofton, JD Mueller, GB Padgett, PP Price, EJ Sikora, IM Small, R Vann, and H Young Reflecting and Looking Forward: Perspectives from “Legends” and “Fresh Faces” of the SSDW (Moderators: Kiersten Wise and Ian Small) The Implementation of a National Response to a New Soybean Pathogen, Phakopsora pachyrhizi, in North America. J Marois Fungicide Resistance in Cercospora sojina: How Did We Get Here and What’s Next? CA Bradley Exploring Mechanisms of Effector-Triggered Susceptibility in the Soybean-Sclerotinia Pathosystem. MG Roth and TJ Ross Contributed Papers (Moderator: Tom Allen) Investigating a Potential Relationship between Xylaria necrophora and Plant Parasitic Nematodes of Soybean. SN Pate, HM Kelly, E Bernard, and LA Schumacher Soybean On-Farm Foliar Fungicide Trial Summary 2020-2022. R Zaia, T Spurlock, R Hoyle, and A Rojas Identifying the Factors Influencing Soybean Disease Management Decisions in Nebraska. AG Mane, SE Everhart, and TA Jackson-Ziems Effect of Fungicides and Resistant Varieties in the Crop Profitability. E Zuchelli, J Barro, and H Kelly Effects of Fungicide Application in Drought Stress Environments on Soybean. J Adcock, H Kelly, and A Shekoofa Fungicides Sensitivity of Athelia rolfsii from Mississippi Fields. S Tripathi, T Allen, A Jimenez Madrid, T Wilkerson Quantification of Athelia rolfsii by qCPR to Assess Cultivar Susceptibility and Fungicide Efficacy for Control of Southern Blight of Soybean. A Connor, T Allen, A Jimenez Madrid, N Aboughanem-Sabanadzovic, T Irby, and T Wilkerson Insecticide Seed Treatments and Their Influence on Sudden Death Syndrome (SDS) in Tennessee Soybean. A Crowder, S Brown, and H Kelly Evaluating Fungicide Sensitivity within the Septoria glycines Population from Mississippi Soybean. J Corser, AJ Madrid, TH Wilkerson, and TW Allen Advancing Soybean Nematode, Sudden Death Syndrome, Frogeye Leaf Spot and Target Spot Management Employing the Latest Seed-Applied Technology. DS Ireland, J Simmons, and A Simon Charcoal Rot Severity and Soybean Yield Responses to Planting Date, Irrigation, and Genotypes. A Mengistu, HM Kelly, QD Read, JD Ray, N Bellaloui, and LA Schumacher Fitness Parameters within the Corynespora cassiicola Population from Mississippi Soybean. TW Allen, X Wang, M Tomaso-Peterson, and TH Wilkerson Soybean Disease Management Programs in Louisiana. GB Padgett, PP Price, D Moseley, F Collins, D Ezell, D Landry, L Lee, TM Monaghan, M Purvis, C Roider, B Woolam Abstract of Student Papers (Moderator: Kiersten Wise) Abstract of Student Poster Transcriptome Analysis Identifies Candidate Genes and Pathways Associated with Target Spot Resistance in Soybean (Glycine max (l.) Merrill). S Patel, J Patel, K Bowen, and J Koebernick Proceedings of the Southern Soybean Disease Workers are published annually by the Southern Soybean Disease Workers. Text, references, figures, and tables are reproduced as they were submitted by authors. The opinions expressed by the participants at this conference are their own and do not necessarily represent those of the Southern Soybean Disease Workers. Mention of a trademark or proprietary products in this publication does not constitute a guarantee, warranty, or endorsement of that product by the Southern Soybean Disease Workers