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. 

  • Scout for Southern Rust on Corn Plants
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    Scout for Southern Rust on Corn Plants

    June 18, 2020

    Posted by Stine Seed in Crop Management

    As of June 14, 95 percent of the country’s corn crop has emerged. Before corn begins to tassel, it’s important to scout for common corn diseases that occur this time of year, including southern rust. Southern rust can be found from the Mid-South to the northern Corn Belt, and can be exacerbated by high temperatures, humidity and strong winds.

    Occurrence
    According to the University of Nebraska-Lincoln’s Institute of Agriculture and Natural Resources, southern rust pustules can result from both urediniospores and teliospores. The institute notes, “The asexually produced urediniospores are dispersed long distances and are responsible for the spread of rust from the deep south to the Northern Great Plains in years where epidemics occur.” Because southern rust is a wind-borne fungus, it has potential to be a wide-spread problem for growers. Southern rust also favors high temperatures, ranging from 80 to 90-plus degrees Fahrenheit, in addition to areas with high humidity and moisture stress.

    Detection
    Scout for southern rust on the leaves of corn plants. Walk your fields, and look for areas of discoloration on the upper leaves. The fungus produces tan and/or orange lesions on the leaves, which are the southern rust pustules clustered closely together on the leaf surface or leaf sheaths. The fungus can also affect the stalk and husk of the plant. The lesions start small, producing a circular-type shape with a halo-like appearance. Once the fungus matures, the lesions spread and turn a brighter orangish-red.

    Differentiating Between Other Corn Diseases
    Tar spot: One way you can detect if it’s southern rust versus another corn disease called tar spot is if the spores rub off with your fingers. While both diseases can first appear as small black, pepper-like spots on leaves, southern rust spores can be wiped off upon touch; tar spot cannot. Learn more in this Ask the Agronomist video.

    Common rust: It’s also easy to confuse southern rust with common rust. According to Purdue Extension, identifying the type of rust depends on the color, shape and location of the pustules. They note that common rust pustules typically appear on both the upper and lower leaf surfaces and are more elongated in shape and scattered across the leaf surface. Southern rust pustules can be primarily found on the upper leaf surface and are more round in shape and clustered together on the leaf surface. Southern rust lesions are also known to be smaller than common rust lesions. Learn more.

    Your local university extension office can also help you determine exactly what fungus you’re dealing with. It’s best to extract and send whole plant samples as soon as you detect the disease. The lab can then examine the whole plant from roots to foliage to determine what disease is present and the best action to mitigate it.

    Management
    Southern rust can be devastating to yields, so you need to determine the level of infection before taking next steps. If symptoms have reached a certain threshold, your situation may warrant a foliar fungicide. Purdue Extension notes, “In high-value corn production, a few pustules on 50 percent of observed plants could trigger a fungicide application.”

    When considering a fungicide for management of southern rust, pay close attention to the timing and application guidelines of that fungicide in addition to the upcoming forecast. Ohio State University Extension notes that fungicide applications need to be made as soon as the first pustules are observed for best results. Spraying when the disease is first detected and confirmed as southern rust can help reduce the spread of the disease as the spores move from plant to plant with the wind. They also note it’s important to start applications with the latest planted fields first because they are higher risk for yield damage. When fungicides are applied, growers need to watch their fields after residual control of that particular fungicide has worn off to ensure the disease does not return.

    If you suspect southern corn rust in your fields, enlist the assistance of your local Stine agronomist to help confirm the disease and discuss your mitigation options. You can also consult the Corn ipmPIPE tool to see if there’s a report of southern corn rust in your county to help you prepare for the  potential risk of the disease reaching your fields.

     

  • How to Spot, Treat Thistle Caterpillars in Midwest Soybean Fields
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    How to Spot, Treat Thistle Caterpillars in Midwest Soybean Fields

    June 11, 2020

    Posted by Stine Seed in Crop Management

    Thistle caterpillars are about as unwanted in growers’ fields as their name suggests. They were an issue for many growers last year, and we’re starting to hear reports of their presence in the Midwest again this year. These pests feed off soybean leaves until they transform into painted lady butterflies. However, before they transform, the caterpillars can cause defoliation in the upper canopy of soybean plants and further injury if left untreated.

    Migration
    Painted lady butterflies, which have orange and brownish black markings, migrate to the Midwest from the southern U.S. states each spring to lay their eggs on the top side of leaves. They prefer to lay on soybean, Canada thistle and sunflower leaves. Because the insects can’t overwinter in the Midwest, thistle caterpillars occasionally strike in large infestations when butterflies migrate to a specific area to lay their eggs.

    Detection
    The butterflies’ eggs are a pale green color and shaped like a barrel with vertical ridges. The eggs may blend into soybean leaves, and growers can more easily spot a network of webs the caterpillars weave along the borders of leaves. These webs provide a protected area under which the caterpillars feed.

    In addition to spotting webs, soybean growers can identify the caterpillars by their spiny, thistle-like hairs that make the caterpillar appear prickly. The hairs seem to stick up in branches with several hairs clustered together. Each caterpillar is about one and one-fourth inches long, and has brownish black and yellow striping running horizontally across its body. The caterpillars feed on the top leaves of plants for about two to six weeks before developing a chrysalis.

    Right now, growers may only be able to detect the larvae. In the coming weeks, the caterpillars should start to emerge. 

    Damage to Crops
    If growers aren’t able to spot the eggs or caterpillars, they may see the damage to the top canopy of their soybean leaves. It’s important to scout soybean fields in early to mid-June to identify a potential infestation. To estimate defoliation, determine the damage done to top, middle and bottom leaves on a soybean plant, averaging the percentages. If defoliation occurs to 20 percent or more of soybean plants’ leaves, it may be time for an insecticide treatment.

    However, some experts warn against overestimating defoliation. Because the caterpillars most often feast on the top layer of foliage, damage is easily visible. Don’t assume that the caterpillar is feeding on the middle and bottom layers of the plant without digging a little deeper. Additionally, these insects tend to gravitate toward the edges of fields, so growers may find it beneficial to scout in the middle of a field and then work their way out.

    Mitigation
    While it may be difficult to prevent thistle caterpillars altogether, soybean growers may have a better chance at staving off large infestations by keeping fields clear of thistles, specifically Canada thistle. Observations of infested fields in North Dakota indicate that thistle caterpillar populations are greater in areas where thistle is established.

    If farmers identify the insects or damage to soybean crops near thistles at the edge of fields, its best to treat by spot spraying a herbicide on the thistle and following up with an insecticide on the healthy plants surrounding the damaged crop. This combination is suggested because using only the herbicide could push the caterpillars further into the field to feed on healthy plants.

    If you have concerns about thistle caterpillars affecting your fields this summer or questions on how to manage the pest, contact your local Stine sales agronomist to discuss your options.

     

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    Start Scouting for White Mold

    June 04, 2020

    Posted by Stine Seed in Crop Management

    Earlier this year we discussed how to get ahead of white mold in 2020. In that article, we discussed the makeup of white mold, the conditions that make the disease thrive and the prevention tactics growers could apply to help prevent it from affecting their fields this year. Over the past few years, especially with the wet year we had in 2019, white mold has begun affecting more fields, sometimes resulting in as much as 15 to 20 percent yield loss. With an estimated 75 percent of soybeans planted and 52 percent emerged, now is the time to begin scouting for white mold to see if it will impact our fields again this year. Here are some tips for white mold detection and a refresher on how to prevent it in the coming years.

    White Mold Detection
    Stine Regional Sales Agronomist Tony Pleggenkuhle notes, “If you get wet weather during flowering of soybeans and it stays that way and you have a heavy canopy, you have the potential to see white mold.” An early and heavy canopy acts as a barrier, trapping in white mold spores and encouraging its spread in the soil below.  

    As for timing of its appearance, growers should start scouting around the R1 to R2 reproductive stages of the plant. “White mold usually shows up when soybean plants blossom and are ready to set pods,” notes Tony. “Early in the season, you could find the white mushrooms that look like little trumpets that release the spores that get in through the blossoms of the plant and infect it that way,” he adds.

    Watch this video where Tony discusses other signs of the disease and how to scout for it this season.

    Tony Pleggenkuhle – White Mold Detection
    https://vimeo.com/354690728/cdb85e5235

    It’s also worth noting that the University of Wisconsin recently updated their Sporecaster app, a great tool to help predict white mold and provide management strategies for the disease.

    The University of Wisconsin-Madison notes, “Sporecaster is designed to predict the probability of white mold apothecial presence.” The app uses GPS coordinates to determine if weather in the area has been favorable for the development of white mold apothecia during the relevant reproductive stages of the soybeans in specific fields.

    Learn more about the app and how to download it here

    White Mold Prevention
    There’s no resistance to white mold and, unfortunately, once it’s detected in your fields, there’s really nothing you can do to stop it in season.

    “The most important thing you can do to prevent white mold from hitting your fields this growing season is to plan ahead,” notes Tony Lenz, Stine corn technical agronomist. “Evaluate your fields and make the necessary preparations to proactively respond to the potential threat of white mold.”

    To prevent white mold, you need to know if a field has a history of the disease. If it impacts your fields this year or has in years past, it’s good practice to plan for it affecting your fields in 2021. Growers can consider specific soybean products that boast white mold tolerance, soybean seed treatments, placing a bio fungicide on their fields in the fall or early spring, and exploring wider row configurations and lower planting populations, to name a few. We’ve also seen some promising results applying fungicide at the R1-R3 reproductive stages.

    Stine Corn Technical Agronomist Tony Lenz discusses different tips for white mold prevention in this video. 

    Tony Lenz – White Mold Prevention
    https://vimeo.com/354670843/251c898000

    White mold can do a lot of damage to yield, and growers need to be proactive in scouting for it this growing season and planning ahead for next year. For more information on white mold and how it can affect your fields, contact your local Stine sales representative.