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Soybean planting is inching along. The April 25 Crop Progress report indicates only 3% of the nation’s soybean crop is in the ground. Tennessee, North Carolina, Nebraska, Missouri, Mississippi, Louisiana, Kentucky, Kansas, Iowa, Illinois and Arkansas have started, but we likely won’t see much movement in the Midwest until corn planting nears completion. However, we are seeing more growers get soybeans in the ground earlier each year.   

“We still have some time before common soybean diseases appear,” says Tom Larson, Stine corn technical agronomist. “But as more growers put soybeans in the ground earlier each season, we run the risk of soybean diseases such as sudden death syndrome (SDS) and white mold making an early appearance as they thrive in cooler, wet climates.”

The big four

White mold and SDS are two of the most problematic soybean diseases growers face each year. They’re prolific and overwinter in the soil, so it’s nearly impossible to get rid of the pathogens once they appear in your fields.

“The soybean diseases we see a lot of as agronomists are white mold, SDS and Phytophthora and charcoal rots,” says Todd Schomburg, Stine director of agronomy. “These diseases typically come back year after year, so it’s important to know what to look for, when to look for it and how to manage the problem throughout the growing season.”

White mold, also known as Sclerotinia stem rot, thrives in cool, humid, wet conditions. The disease can be somewhat easy to detect as it has a cotton-like appearance. Look for white, raised spots on plant stems. Symptoms typically appear between the R3 and R6 growth stages. White mold can be detrimental to yields. For growers who experience high white mold pressure every year, there are soybean varieties that offer some resistance to the disease. Crop rotation to small grains and corn can also help mitigate the future spread of white mold.

“White mold can cause significant yield loss,” says Larson. “In some instances, growers may post up to a 10% bushel per acre yield loss. And that number can be a lot higher depending on how early it affects the soybeans. We’ve seen it devastate fields in my region in Iowa.”

SDS prefers cool, wet soils. Symptoms typically appear between R1 through R6 growth stages and can start as random yellow spots between leaf veins. More severe cases evolve to include soft, rotten roots, stem discoloration, complete necrosis of the leaf tissue between the veins, yellowing of leaves and leaf drop. Growers can manage SDS by using tolerant varieties and seed treatments (nematicides). Crop rotation, tillage, planting known SDS fields later and avoiding compaction can also help control the disease, as well as planting into warmer soils. Soybean cyst nematode issues can also exacerbate the disease.

“SDS is one of the major yield-robbing diseases for soybean growers,” says Schomburg. “In fact, experts from Iowa State University Extension and Outreach conducted a study and found that, in areas with severe infestation, SDS can cause up to a 40% yield loss.”

Phytophthora leaf and stem rot is another common soybean disease that occurs in cool, wet conditions. Symptoms appear between VE and R6 growth stages and can include yellowing of leaves, soft/rotting stems and roots and wilted plants. According to Crop Protection Network, “The most characteristic symptom of Phytophthora root rot is a dark brown lesion on the lower stem that extends up from the taproot of the plant.” Tillage, seed treatments and planting resistant varieties are recommended to manage the disease. Some varieties are more susceptible to Phytophthora, so if you have a field history of the disease, it’s important to consult your local Stine agronomist to walk you through the right variety options.

Unlike the other common diseases in our big four list, Charcoal rot thrives in warm, dry conditions. Early symptoms include red to brown lesions on the roots and lower stems. Later on, black specks appear in the same area. When conditions worsen, the disease reaches the canopy and can lead to yellowing of leaves and leaf drop. The best time to scout for charcoal rot is from R5 through R7. A good fertility program mixed with moderate planting populations can help keep mitigate the disease. Selecting the right variety, crop rotation and residue management can also aid in the process.

Other not-to-be-disregarded soybean diseases

Like the corn diseases we discussed last week, there are a number of soybean diseases that, while less common, can’t be overlooked. 

Soybean rust is environmental and occurs in hot, wet conditions. While not as prevalent in soybean acres, when conditions encourage growth, it can pose a significant yield risk. According to the University of Minnesota Extension, “Under favorable conditions, the pathogen can cause yield losses greater than 50%.”

Scouting for soybean rust should take place regularly throughout R1 and R6 growth stages. Early symptoms include tan to reddish-brown colored leaf spots on the lower canopy that can blister to release spore masses, which can spread quickly. Fungicide applications are necessary to control the disease.

Frogeye leaf spot — a soil-borne disease — can also lead to significant yield loss. This disease thrives in hot, wet conditions and should be something growers scout for regularly after frequent rains. The best time to scout for frogeye leaf spot is between the R3 and R6 growth stages. Symptoms can include red to red-brown spots on leaves with purple halos surrounding the spots. These spots are often irregular in shape and size. To manage the disease in-season, fungicides can be applied. As the disease survives in crop residue, tillage is recommended.

Brown stem rot occurs in cool, wet conditions and is residue related. Scouting should take place between the R4 and R6 growth stages. Initial symptoms can include browning of the stems and leaf tissue between the veins. Sometimes the stems can look healthy but may be rotting on the inside. After the disease spreads, lodging can occur, which leads to harvest complications.

“Brown stem rot is more prominent in susceptible soybean varieties, so it’s important to work with your Stine agronomist on your best seed options,” says Schomburg. “Crop rotation can also be effective in treating the disease.”  

Other soybean diseases such as sunscald, bacterial blight, bacterial pustule, cercospora, downy mildew, stem canker and target spot might also be problematic this year. Learn more about those diseases and tips for scouting here.

For more information on common soybean diseases and how to keep them at bay now and in the future, reach out to your local Stine agronomist or sales rep. University extension services also offer valuable advice on detection and mitigation strategies for these diseases.

Corn planting is underway. According to the latest National Agricultural Statistics Service Crop Progress report, Kansas, Kentucky, Missouri, North Carolina, Nebraska, Pennsylvania, Tennessee and Texas have crops in the ground.

“As planting season progresses, it’s a good time to walk through the different crop diseases growers need to look out for,” says Tom Larson, Stine corn technical agronomist. “There are symptoms that can appear as early as emergence, but luckily there are strategies growers can execute to get ahead of the problem.”  

The most common corn diseases

Growers are all too familiar with most corn diseases, but there are a handful that can wreak havoc on fields year after year as environmental conditions allow. Some of the most common corn diseases growers should be on the lookout for include:  

Tar spot. Tar spot overwinters in corn residue and can thrive in hot, wet conditions. Symptoms include small, raised black spots that resemble fisheyes scattered on both sides of the leaves. Unlike some foliar pustules, tar spot cannot be scraped off leaves. Scouting for the disease is recommended between the R3 and R6 growth stages.

“Tar spot is a big concern for growers as it can cause significant yield loss,” says Tony Lenz, Stine corn technical agronomist. “If it’s been an issue for you in the past, there are some resistant hybrids that can help keep the disease at bay, but a mix of crop rotation and tillage is also recommended.”

Gray leaf spot. A foliar disease, gray leaf spot can overwinter on residue and poses a significant yield threat. It thrives in hot, wet climates and has symptoms similar to other foliar diseases. It can be distinguished by small, pinpoint lesions that form a yellowish halo and eventually produce much longer lesions. Gray leaf spot is typically detected between the V15 and R4 growth stages. 

“Rotation is key here as the disease is more prevalent in corn after corn fields,” says Lenz. “Other options to mitigate gray leaf spot include using a resistant hybrid and applying strobilurin and triazole-type fungicides.”

Northern corn leaf blight. This disease thrives in cool, wet conditions and can be detected by tan streaks or lesions that appear parallel to the leaf structure. The best time to scout for northern corn leaf blight is from V15 through R4. The disease overwinters in corn residue, so growers who have had it in their fields should consider resistant hybrids and other modes of action like fungicides and tillage.

“Tillage is a solid option for growers experiencing heavy Northern corn leaf blight pressure,” says Larson. “In no-till systems, rotation can help reduce spores.”

Common rust. Not to be confused with southern rust, common rust is environmental and prolific in cool, wet conditions. Symptoms crop up between V12 and R4 and include sporadic rust-colored pustules, which can be detected on both sides of the leaves.

“Fortunately, common rust typically does not cause significant yield damage. And there’s not a lot growers need to do in-season for the disease,” says Larson. “That said, it is something growers should get in front of by bringing in a resistant hybrid for next planting season.”

The less common — but not to be disregarded! — corn diseases

While some corn diseases are more prevalent and prolific than others, there are some that, while less common, can’t be ignored for another year.

“Stalk rots and ear molds can rear their ugly heads later in the growing season,” says Bill Kessinger, Stine corn technical agronomist. “And many other corn diseases can threaten yield early on. Scouting is critical from emergence through harvest for any corn field,”

Early-season diseases
As soon as corn is in the ground and emergence begins, growers need to look for seed decay, seedling blights and root rot. These early-season diseases favor cold, wet soils and can result from compacted soils. Symptoms can be detected by digging up the seed to look for any brownish-black discoloration of the mesocotyl region. Seed can have a rotting appearance as can the roots. Later, these diseases can result in stunted plants and wilting.

Mid- to late-season diseases
Ear molds appear later in the growing season. They are environmental and caused by the same pathogens that trigger stalk rots. Pathogens produce mold on the ear that can vary in color. As a reminder, ear molds can produce mycotoxins that are dangerous if ingested by livestock.

Foliar diseases like Anthracnose leaf blight and Goss’s wilt can appear later in the growing season. Symptoms of Anthracnose leaf blight include oval-shaped lesions that first appear on the lower leaves, working their way up and turning black. Goss’s wilt appears as wavy lesions on the leaves that exude a water-like substance.

Other foliar diseases that may appear later in the season include Physoderma brown spot, crazy top, Holcus leaf spot and Stewart’s Wilt. And Anthracnose stalk and top dieback are vascular infections of leaf spot that can be problematic. Find more information on these diseases in this article.

“Regardless of the corn disease, growers have options. A healthy mix of choosing the right hybrid and fungicide and employing crop rotation and tillage can make all the difference to yield,” says Kessinger.

For more information on common corn diseases and how to keep them at bay now and in the future, reach out to your local Stine agronomist or sales rep. University extension services also offer valuable advice on detection and mitigation strategies for these diseases.

Citation

Sept. 2017, Corn Diseases, Iowa State University of Science and Technology, Iowa State University Extension and Outreach.

Our Stine agronomy department is working with sales team members to install METOS^® weather stations in our Master Yield in the Field (MYIF) plots. We’re confident this effort will provide more actionable data to our grower customers.

As our MYIF plots are located throughout the United States, these weather stations will provide us with important agronomic data in different regions and growing environments.

“The weather stations track accurate rainfall, wind speed and growing degree days in real-time without relying on public data,” says Todd Schomburg, director of agronomy.

Each station is equipped with a solar panel, wind speed sensor, and automated rain gauge that sends valuable information directly to the FieldClimate cloud, giving immediate access to the data from any smart device.

“This technology is the next evolution in weather stations,” says Schomburg.

Specifically, METOS notes the stations are designed to monitor basic meteorological parameters, including rain and temperature, humidity, solar radiation, wind speed and soil characteristics such as moisture and soil temperature (if installed with a soil probe). They also have packages that offer applications that detect frost, leaf wetness, disease models, evapotranspiration, hydrology, etc. Data is measured in five-minute intervals and delivered to the FieldClimate cloud every 15 minutes.

“These elements will help determine when soil is ready for planting, conditions are ideal for disease proliferation, and so much more,” says Schomburg. “We’re excited about how these stations will help improve crop management throughout the planting and growing seasons and deliver better data for our customers.”

Another unique advantage to the METOS weather stations — they’re environmentally friendly. When sun is available, the unit can recharge its battery through the solar panel connected to the device.

“The units are cost-effective, environmentally sound and easy to use,” says Schomburg. “Some have been installed and we’re already receiving great data that will help us determine when to get the plots in the ground.”

More on our MYIF plots
Stine plants at least two MYIF plots per sales region each year. With 36 regions across the country, we’re planting nearly 70 plots this year in collaboration with our grower partners. MYIF plots have between six to 10 Stine corn products, including our newest hybrids along with experimental products to look at as future hybrids in the lineup. To ensure a level playing field, we also have up to two national competitor brands and, when available, a local competitive brand in the mix for comparison purposes.

“The main goal of our Master Yield in the Field plots is to derive as much data possible from our corn products and those of our competitors,” says Schomburg. “We monitor everything from emergence scores and stand counts to ear and tassel height, in addition to different biologicals and inputs used and planting populations and row configurations.”

These plots are valuable in producing the highest quality data for our growers and make a great training resource for our sales team.

“We also use our Master Yield in the Field plots for training,” adds Schomburg. “They allow our seed dealers and sales team members to study the products and understand how they perform in different environments. They’re extremely valuable to our operations all around.”

For more information on our MYIF plots and data generated from our weather station program, contact your local Stine sales rep or regional sales agronomist.