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. 

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    Scout for Tar Spot this Growing Season

    May 16, 2019

    Posted by Mike Smith in Crop Management

    Last year, we saw the disease tar spot in alarming number of corn fields for a variety of reasons, and it’s likely we’ll cross paths with it again this year because of the extra moisture we’ve received (and continue to receive) across the Corn Belt and South. Get to know the signs of tar spot and how you can help mitigate the disease so that you’re prepared for its impending arrival this summer.

    What is tar spot?
    Tar spot is a fungal disease that affects corn leaves and husks. According to Crop Protection Network, the disease was primarily located in parts of South America, Central America, the Caribbean and Mexico until 2015. The disease has since spread to the United States, affecting areas such as Illinois, Iowa, Indiana, Wisconsin, Ohio, Michigan and Florida. The spores survive on top of the soil during the winter and resurface the next growing season. The fungus, also known as Phyllachora maydis (or P. maydis), forms stromata on the leaves of the plant that can cause defoliation, which can directly affect grain fill around the development stage in corn. The spores are known to travel via wind or rain, putting your entire corn crop at risk of infection if detected.  

    How to detect tar spot
    This foliar fungus produces small, irregular raised black spots (stromata) on the leaves of the corn plant, affecting both lower and upper surfaces. If wet conditions persist, some growers may even see a gel-like mass form on top of the spores. In some instances, brown spots that resemble fish eyes may appear. These are called fisheye lesions and occur because of a different fungus called Monographella maydis, also referred to as tar spot complex. Michigan State University Extension states that “growers are often describing the visual symptoms of the disease as leaves that have been speckled by black paint or motor oil.”

    Tar spot can be mistaken for southern rust, so enlisting assistance from a local agronomist or university expert can help correctly classify the disease. One obvious distinction is tar spot stromata cannot be rubbed off the leaf, whereas corn rust pustules can.

    Methods for management
    Growers should consider fungicides if tar spot is detected in their fields. For example, Lucento is a newer fungicide that can help control tar spot and can be applied when the disease first appears through the R4 growth stage in up to two applications. According to FMC, the creator of Lucento, the fungicide “attacks disease from the inside out by delivering active ingredients through translaminar and acropetal movement that provides uniform leaf distribution, disease protection and keeps working long after application for control that lasts.”

    Fungicide applications are difficult to time with this disease. Inoculation can occur without visible symptoms for 10–14 days. The best indicators of when to apply fungicides for tar spot are:

    • Disease present in the area in previous year
    • Warm, humid conditions followed by wet periods (cloudy days that allow leaf surfaces to stay moist into mid-morning)
    • Tassel through R5 or dent. Fungicides protect photosynthetic tissue up to and through flowering and grain fill. These are critical times to protect with fungicides.
    • Protection from secondary infections from fungicides can be beneficial (stalk rots and mycotoxins)

    I also encourage growers to respect the rotation. Tar spot can thrive in corn, but it’s not known to survive on soybeans. If tar spot is a serious issue for you in 2019, make sure you give that field a break in 2020, or swap it for another crop to help reduce the risk of tar spot in coming years. Also consider tillage to help reduce the tar spot that may be overwintering in your soil.

    If you think you’ve detected tar spot in your fields, don’t delay. Reach out to your local extension office with a sample to confirm the disease. The good news is there are ways to manage tar spot before it devastates your crop.

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    Don’t Switch Hybrids … Yet!

    May 09, 2019

    Posted by Stine Seed in Planting

    A question we’re hearing from growers across the Corn Belt as of late is, “should I switch from my full-season hybrid to an earlier maturing hybrid?” This question is complex because not every situation is the same, but the short answer is “not yet.”

    Frequent spring rains are keeping some growers out of the field in parts of Missouri, Kansas, Illinois, Kentucky and Ohio, while other areas in South Dakota, Minnesota and northern Iowa are still dealing with the aftermath of heavy snow in April. For some growers, it may be a week or more before they even think about turning a wheel. What’s important for growers in times like these is to not let your anxiety get the best of you; stick to your planting plan as long as you possibly can. Here’s why.

    Historically, full-season hybrids yield higher than early-season hybrids. Studies show that even if you lose some bushels planting full-season hybrids in mid-May, the yield loss is more significant when switching to earlier maturities. According to Penn State Extension and the Penn State Agronomy Guide, “in most areas, switching to a shorter than adapted hybrid maturity should not be considered until at least the last week of May.” In areas that plant longer-season maturities, corn may not even need to be in the ground until mid-May, so there’s no need to rush if the ground is still wet. This applies to states such as Wisconsin, Minnesota, Iowa, Nebraska and Illinois — areas still well within the optimal corn planting dates for their maturities.  

    Another thing to consider is growing degree days. According to Penn State Extension, if you are questioning a switch, you should consider the approximate number of growing degree days left in the season before a fall killing frost could strike. Remember, heat units drive maturity. If your corn has more time to mature, the more bushels you’ll add. Switching to an early-season hybrid may rush the process.

    Stine Technical Corn Agronomist Tony Lenz recommends holding off on adjusting hybrid maturities until mid- to late-May, and even then, he only recommends switching to a five to seven day earlier maturity than your full-season hybrid. He notes, "these recommended dates can vary from region to region because of factors such as grain prices, drying costs and whether your crop is used for grain or for livestock feeding."

    If field conditions have prevented you from getting into the field, don’t act prematurely. Stick with your planting plan. If it gets closer to late-May and things still haven’t progressed, contact your local extension office or Stine agronomist to discuss your options before switching to a different hybrid.

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    Planting Progress: Who’s in the Field, Who’s Waiting It Out?

    May 02, 2019

    Posted by Stine Seed in Planting

    This week’s Crop Progress Report by the U.S. Department of Agriculture’s National Agricultural Statistics Service (NASS) confirms what Stine agronomists report in their regions. While planting is underway throughout the Midwest and in the Mid-Delta South, areas of the northern Corn Belt aren’t quite there yet. This is likely because of the unseasonable weather conditions this region experienced early this spring.

    According to the report, 15 percent of corn is planted, with three percent emerged. That’s right on par for last year’s average at this time. For soybeans, three percent of planting is complete, which is similar to last year’s average. This data is based off the 18 states that planted 92 percent of the corn acreage and 95 percent of the soybean acreage in 2018.

    In the field
    Planters are rolling steady in the South and southern Corn Belt, including in Kentucky, Kansas, Missouri, North Carolina, Tennessee and Texas. Some corn is even up in these areas. Consistent warmer temperatures and less precipitation in these regions during early spring encouraged growers to start planting early. However, Stine Corn Technical Agronomist Mike Smith notes that growers in Mississippi and Louisiana are still battling wet soils.

    Waiting it out
    Storms in mid-April dumped heavy snow and rain in many areas of the northern Corn Belt. According to Stine Corn Technical Agronomist Tony Lenz, in Wisconsin, South Dakota, North Dakota, Minnesota and Iowa, conditions depend on whether you’re north or south of the I-90 corridor. Cool, wet and even some water-logged soils persist in these areas. The NASS Crop Progress Report shows that planting has yet to begin in South Dakota, while in Indiana, Michigan, Minnesota, North Dakota, Ohio and Wisconsin, less than five percent of the corn crop is in the ground. In addition to unseasonable weather conditions, Director of Agronomy Todd Schomburg notes that some growers in this region may have experienced a delay because they were unable to prep their fields last fall due to wet conditions. Many growers are busy getting their fields ready with tillage and anhydrous applications before getting in the planter.  

    Whether you’re in the field or counting down the days until you can get started, now is a great time to turn to the expert advice of your local Stine sales agronomist. Their product and crop management knowledge can help you maximize the potential of every acre.