ASK THE AGRONOMIST BLOG

Stine’s Ask the Agronomist blog is your source to the latest information from our expert team, including advice and insight on field practices, product recommendations, planting and harvest updates, new technologies, crop management, innovative research and information about how to keep your farm operation running smoothly year round. 

  • 5 steps to protect your crop after a storm
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    5 steps to protect your crop after a storm

    June 23, 2022

    Posted by Stine Seed in Crop Management

    Areas of the Midwest recently experienced hail and severe winds from storms, which resulted in damaged crops. As we’re officially in the summer growing season, growers are likely on high alert for what a severe thunderstorm could mean for their emerged fields. Here are a few recommendations from our agronomy team on how to assess and protect your crops after a storm:

    Step 1: First things first — scout. Get out in the fields, look at different sections and determine the extent of the damage. Also, note the growth stage of the plants in the field, as that may impact the next steps.

    Step 2: If it’s early enough — wait it out. Experts from the Nebraska Institute of Agriculture and Natural Resources said, “With any early-season hail damage, the most important first step is to give the crop time to regrow before addressing damage and making major decisions.” For corn, it’s important to know where the growing point is. For anything under V6, the growing point is still underground so you are likely safe from any long-term damage. For soybeans, it’s a bit trickier as the growing points are above ground immediately after emergence. Experts say to look for broken nodes and damage to stems below the growing point. Even if damage is detected on soybeans, our agronomists recommend waiting up to five to seven days before considering additional steps such as replant.

    “Unless the hail or wind has knocked everything over, growers should wait it out,” says Tom Larson, corn technical agronomist for Stine. “There’s no reason to jump the gun right after a storm.”

    Step 3: If after five to seven days you see additional damage to crops resulting from the initial damage (e.g., lodging or plant discoloration across fields, any indication that the crop isn’t properly taking up nutrients, or an increase in bacterial disease), it may be time to consider secondary options.

    Step 4: Consider fungicides only in severe fungal infestations. According to a recent article by Connie Strunk, South Dakota State University Extension Plant Pathology Field Specialist, “Applying fungicides on hail-damaged plants should only be warranted if there are significant fungal diseases developing on these plants.” If you have heavy fungal pressure, applying a fungicide may be a consideration to help protect the yield potential of the plant. Connie notes fungicide applications for soybeans are best between R1 and R3 — and for corn, VT and R1 when warranted. On the other hand, if fungal pressure is mild to moderate, it may be best to consult your local agronomist before spending money on additional inputs.  

    “When a plant is under stress, it’s going to be vulnerable to diseases,” says Larson. ”Growers really need to do their due diligence and scout frequently to see if a post-storm fungicide application is warranted. Stine agronomists can help growers determine if a fungicide might make sense.”

    Step 5: Replant only in severe cases. In most cases, your corn should be fine unless heavy disease pressure persists after fungicide passes or in severe wind events where lodging or greensnap occur across fields. But, for soybeans, if severe damage is noticed in several of the nodes, replant may be a consideration. Before doing so, we highly recommend consulting with your local sales rep or agronomist to determine the best path forward.

    “If you have a total loss, there are charts out there that can help you determine the percentage basis for replant,” says Larson. “But growers also need to look at it from an insurance standpoint. They need to ensure they’re covered in this regard.”

    For more tips on managing your crops following a storm, reach out to your local Stine representative.

  • Scout often for these common soybean diseases
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    Scout often for these common soybean diseases

    April 28, 2022

    Posted by Stine Seed in Crop Management

    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.

     

  • Don’t let common corn diseases affect your yield game
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    Don’t let common corn diseases affect your yield game

    April 21, 2022

    Posted by Stine Seed in Crop Management

    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.