C.O.R.N. Newsletter: 2024-16

Episode 9 of Battle for the Belt is now available: https://www.youtube.com/watch?v=I3zTyGvt1_s

In Episode 9, Dr. Horacio Lopez-Nicora, Ohio State Extension Soybean Pathologist, and PhD student, Jenna Moore, speak about early planting considerations for disease management and a couple of current research projects in their lab.

Early Planting Considerations:

Figure 1. Disease triangle showing three required components (susceptible host, virulent pathogen, and conducive environment for disease to occur.

Understanding how to manage diseases is hinged on the disease triangle. Diseases occur when all three components of the disease triangle intersect: a susceptible host plant, a virulent pathogen, and conducive/favorable environmental conditions (Figure 1). These components must align for disease to develop. For example, soil-borne pathogens like Phytophthora and Pythium can cause severe stand reduction, particularly in warm soil temperature fields with poor drainage that allow for sitting water. On the other hand, the fungus that causes sudden death syndrome (SDS), can cause more severe disease under cool and wet conditions but become less of a problem as the soil warms and dries out.

Early planting in Ohio generally means that you will likely plant soybeans in cool and wet soils, which can make the perfect environment for some of our most detrimental diseases.

To manage these diseases, you need to know your field history and which diseases you are dealing with because each disease can be mitigated by using different resistant varieties and seed treatments to protect the crop. 

SCOUTING every year is extremely important to be able to identify disease pressure and create a management plan for that field. Identifying soil-borne diseases can be challenging during the scouting process due to their similar symptoms. If help with diagnosis is needed, samples of affected plants can be sent to the Ohio State Soybean Pathology and Nematology laboratory. It is essential to have a laboratory validate and confirm the disease diagnosis. With the support of the Ohio Soybean Council, soybean growers from all over the state can once again submit soybean samples showing symptoms of sudden death syndrome (SDS) to the laboratory. We look forward to receiving your SDS samples! You can conveniently complete the SDS submission form and send your samples to:

Attn: Horacio Lopez-Nicora, Ph.D. (lopez-nicora.1@osu.edu)
110 Kottman Hall 
2021 Coffey Rd., Columbus, Ohio 43210

After properly identifying the disease there are three main practices to fight these diseases. The first is soybean variety selection. Choosing a soybean variety that is resistant to the specific pathogen you are dealing with is one of the most important disease management decisions. The second is using a disease-specific seed treatment. And finally, well-drained soils to avoid compaction and saturation.

Battle for the Belt Disease Update:

Corn and soybean seedling samples are collected within seven days after the emergence of all five planting dates at each location in order to identify diseases in the plants and surrounding soil. Two different approaches are implemented to evaluate the samples: a traditional approach involving plating and growing the pathogen for molecular diagnosis, and a metabarcoding approach that extracts DNA and characterizes the microbial community present in a sample.

In 2023, we observed different structures in the microbial community of seedlings and soil, depending on the planting dates, locations, and crops. Last year we experienced a cool and wet early season, followed by a prolonged dry spell during planting, resulting in an increased prevalence of organisms such as Rhizoctonia. Consequently, the presence of pathogens and the occurrence of diseases vary based on the planting date, Ohio region, and crop. This emphasizes the importance of understanding your field's history.

What’s happening in the field?

At the Northwest location, the second date was planted on May 23^rd (Table 1). At Northwest, our first planting date (May 16^th) for both corn and soybeans were emerged, with corn being further along in growth than the soybeans (Table 2). Last week at the Western location, the first planting date (March 26) reached V6 in corn (Table 2), meaning the growing point is now above ground and sidedress applications will occur soon. Planting date four was planted on May 24^th. At the Wooster location, the fourth date was planted on May 21^st, with optimal planting conditions. While planting date one and two are progressing quickly with the warm weather.

Table 1. The planting date conditions for planting date four at the Western Agriculture Research Station, planting date two at the Northwest Agriculture Research Station, and the third planting date at the Wooster Campus.

Table 2. Weekly weather conditions for each updated planting date at the Western Agriculture Research Station, Northwest Agriculture Research Station, and Wooster Campus, with day of planting, soil, air temperature averages, and Growing Degree Days (GDDS) from May 20 to May 26. Information from CFAES Weather System (https://weather.cfaes.osu.edu/).

Many counties across Ohio are noticing slug damage in their fields this year. Slugs prefer fields that are no-till, especially fields where cover crops are grown. Slugs feed directly on the soybean, causing both seed and foliar damage that can result in complete loss of the plant. Management is difficult due to the nocturnal nature of slugs. During the day they take shelter under leaf litter and other debris in the field (Figure 1). Adding to management difficulties, slugs have all life stages present at any time in the field (eggs, juveniles and adults) (Figure 2). To learn more about slugs a newly updated fact sheet is available and can be viewed here: https://aginsects.osu.edu/sites/aginsects/files/imce/Slugs%20on%20Field%20Crops%20_%20Ohioline.pdf

Despite the growing concern, little is known about slug populations across Ohio. To better understand Ohio slugs, we are participating in a multi-state project  funded by the United Soybean Board, to monitor slugs in soybean fields across the region. Each field will be monitored using shingle traps for 9 weeks (3 weeks before plant, and 6 weeks after plant). Shingle traps consist of a 1-sq.ft. white roofing shingle secured to the ground with tent stakes. These traps provide a refuge for slugs to hide under during daylight. Each week, traps are checked in the morning by lifting the shingle and counting the number of adult and juvenile slugs underneath each trap. The data collected from this study will allow us to have a better understanding of the slug variations in Ohio and across the region.

Figure 1. Slug found on underside of leaf litter. 

Figure 2. Slug eggs.

While reports of slugs in fields are high across the state, the average number of slugs found under the shingle traps across Ohio remains low. The highest average from any reporting field in Ohio has been 1.8 slugs/shingle in Seneca County. The figure below shows the average number of slugs found under the shingle trap in each county from May 20^th – 26^th (Figure 3). The majority of counties in Ohio are reporting low numbers of slugs found under the shingle traps. Seneca had the highest average number of slugs (1.8) followed by Wayne (1.7). It is important to note that low slug numbers under shingle traps does not necessarily mean there are low numbers of slugs in the field, monitoring the number of slugs underneath traps slug trap numbers using shingle traps and analyzing what those numbers mean for overall slug pressure in Ohio is  

Slugs in Ohio

May 20^th – May 26^th

Figure 3. Average slugs captured from May 20^th to May 26^th. The bold number on the left indicates the average slug count for the week, followed by the standard number on the right which indicates the total traps set up in that county.

Please join Drs. Maggie Lewis, Horacio Lopez-Nicora, and Aaron Wilson on a webinar titled Weather Trends and Pest and Disease Impacts on Soybeans on Tuesday, June 25, 2024, from 8:30-10:00 am ET. We will update the latest climate trends pertinent to soybean-related pests and diseases, including increasing winter temperatures and extreme weather. We will investigate how abiotic stressors linked to global climate change impact insect pests, from changes in population growth rates to geographic range and phenology. We will analyze the impact of weather patterns on the occurrence of diseases as well, including sudden death syndrome, frog eye leaf spot, white mold, and seedling rot caused by water molds (Phytophthora and Pythium). We will discuss effective management techniques for these stressors and offer innovative strategies to help ensure sustainable soybean production. Please register for this webinar at https://go.osu.edu/soy_climate24. We have applied for 1 Integrated Pest Management and 0.5 Crop Management CCA credits. Please visit the registration site for updates.

Dr. Maggie Lewis is a Research Scientist in the Department of Entomology at The Ohio State University. She is broadly interested in advancing sustainable insect pest management and characterizing climate change impacts on agroecosystems. Her current research uses soybeans and the soybean aphid as a model system to understand how climate stress will shift pest and beneficial insect population dynamics.

Dr. Horacio Lopez-Nicora is an Assistant Professor, Department of Plant Pathology at The Ohio  State University. His research falls into three areas: early detection and surveillance for soybean pathogens; pathogen ecophysiology and population biology; and soybean-pathogen interactions and host resistance. His lab addresses the short- and long-term stakeholder priorities of soybean pathogen management in Ohio through a commitment to extension work and development of practical solutions for growers in Ohio. Additional information can be found on Dr. Lopez-Nicora’s site at Ohio State University and The SCN Coalition.

 Dr. Aaron Wilson is an Assistant Professor, Agriculture Weather and Climate Field Specialist with the Department of Extension in the College of Food, Agricultural, and Environmental Sciences at The Ohio State University. He is also the State Climatologist and principal research scientist at the Byrd Polar & Climate Research Center. Aaron’s research and engagements focus on observed and projected changes in climate and bridging expertise to improve decision making and effective climate change action.

This webinar is sponsored by Ohio State University Extension Integrated Pest Management Project (NIFA-GR125062). We would also like to thank the Ohio Soybean Council for their continued support.