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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    Traits and Tips for Managing Black Cutworm

    May 23, 2019

    Posted by Stine Seed in Crop Management

    Black cutworm is likely to start appearing soon if they haven’t already. Some fields where corn has emerged may already be experiencing black cutworm damage. Their movement is sporadic, but they typically affect corn, wheat, tobacco and vegetable fields. Growers need to be diligent about scouting for black cutworm this growing season to avoid yield loss. Here are a few tips to keep in mind when scouting for and managing black cutworm.

    Scouting
    Black cutworm arrives in growers’ fields as moths, where they lay eggs that hatch as larvae. The larvae damage corn crops as they begin chewing the early-stage plants around V2 or V3. Black cutworm larvae are grey to black in color with dark bumps alongside their body. Iowa State University Extension and Outreach describes them as having “grainy, light grey to black skin and four pairs of fleshy prolegs on the end of the abdomen.” They are often times confused with armyworms or other types of cutworms, so getting an official confirmation of the pest may be important to ensure you’re implementing the best management practices.

    Scouting typically begins in April and May in the form of monitoring flight paths of black cutworm moths through pheromone traps, which is discussed in more detail below. After black cutworm has transformed to larvae, growers need to look for a few things as they scout fields during the early stages of corn development. Experts recommend scouting for damage every week up until the V5 stage. This process includes checking several areas of your field, not just one. Start with the fields that were planted first. Look in the weeds and grassy areas, or if you have a cover crop, moths could lay their eggs there as well. Walk the rows and look for some of the key symptoms, including very irregular cut leaves, necrosis on both ends of the plant, wilting and leaf discoloration. If you detect areas with these symptoms, you can dig around the plants to carefully extract the larvae to confirm their presence. Economic thresholds vary dependent on your environment, but two to five black cutworms per linear row should be detected before treatment is considered. Check with your local extension office to get the appropriate threshold for your region.

    Pheromone Traps
    As black cutworm moths begin their migration, pheromone traps can be set to capture the moths. Experts can then estimate potential infestation levels in the area and help predict their cutting dates by incorporating growing degree days. This step essentially helps experts forecast the presence of black cutworms in your area and when they are predicted to emerge as larvae and begin feeding on plants. Your local extension offices should have a list of anticipated cutting dates, so consult with their experts if you suspect black cutworm infestation. It’s also important to know that pheromone traps alone should not be the only management practice implemented to help ward off the pest.

    Bt Hybrids
    Stine Agrisure® Viptera® brand corn can offer some suppression of black cutworm. The Agrisure Viptera 3110 trait stack provides season-long control from black cutworm and other insects such as the European corn borer, southwestern corn borer, southern cornstalk borer, corn earworm, fall armyworm, dingy cutworm, beet armyworm, western bean cutworm, sugarcane borer and common stalk borer. These are represented as -20 or -20/LibertyLink® hybrids.

    Stine® Agrisure Duracade® brand corn is another product that can help combat black cutworm. For example, Stine Agrisure Duracade 5222 E-Z Refuge® blend brand corn is an all-in-one system for corn pest management. The product boasts two modes of action to help tackle yield-robbing lepidopteran corn pests such as black cutworm. We recommended Stine Agrisure Duracade hybrids R9540-32 Blend, R9529-32 Blend, R9653-32 Blend, R9734E-32 Blend, R9744-32 Blend, R9734-32 Blend and R9739E-32.

    Although helpful in mitigating black cutworm, Viptera and Duracade treated corn must be ingested by the cutworm for it to die off, so it’s more of a reactive treatment to suppress black cutworm. Consult the 2019 Syngenta Stewardship Guide for rules and regulations before purchasing Stine Agrisure products.

    Insecticides
    If you don’t have Bt traits planted and you’ve hit your economic threshold for black cutworm, then it’s time to spray. According to the University of Minnesota Extension, post-emerge insecticides work well against black cutworm infestations. Experts recommend T-band applications for granular insecticides. As always, read and follow labels and use rates before applying an insecticide.

    For more information about scouting for black cutworm and best management practices, contact your local Stine agronomist or university extension office.

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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.