• What to Scout in Corn Now

    What to Scout in Corn Now

    August 11, 2016 12:00 PM
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    “Loss of 1,000 plants per acre is a 5- to 7-bu. loss,” says Brad Beutke of CropTech and presenter at the 2016 Farm Journal Corn College in Albert Lea, Minn. Examine where grain loss came from to limit financial losses next year.

    Stand

    Uniform stand establishment is a critical building block to high yields. When plants get behind or your planter leaves skips, doubles or misplaced seed in the field, yield is lost nearly immediately.

    It’s typically pretty easy to tell when a plant gets behind. Look for skinny stalks and small or underdeveloped ears. Since it fell behind early, it essentially became a weed and had to fight with its neighbors for sunlight, water and nutrients. Big plants usually win that fight, which means plants with delayed emergence don’t pay out.

    One of the easiest ways to have uneven emergence is uneven planting depth. When a plant is deeper or shallower than surrounding plants, it’ll likely be delayed because it has to work harder to break through the surface. Alternately, the seed is so close to the surface it can’t take absorb water to germinate.

    Uneven planting depth isn’t the only hazard of planting. Skips, doubles and misplaced seed can decimate yields, too. You can identify whether a true skip, a double or a misplaced seed has occurred by heeding several rules of thumb:

    • Skips can be identified by a missing plant with even plant spacing on either side.
    • Doubles show two plants close together with even plant spacing on either side.
    • Misplaced seed results in uneven spacing, often a result of a delayed seed drop.

    “We see a lot less doubles than we used to because of metering technology,” says Farm Journal Associate Field Agronomist Missy Bauer. “In a double, one won’t produce a harvestable ear.”

    You’re more likely to see misplaced seed than a double or skip. “Planting speed is a big culprit of misplaced seed,” Bauer adds. “Losses from planter speed show up in ear size.”

    If you’re going too fast, seeds can bounce or get caught up in seed tubes, delaying seed drop. That drops a seed where it doesn’t belong, misplacing seed and throwing off your picket-fence stand.

    Roots

    Since planting depth can play a large role in stand development, it’s essential to evaluate your roots. You can measure planting depth even at this point in the growing season.

    “Planting problems show up at harvest,” Beutke says.

    After digging up a root mass, trim brace and crown roots and clear the plant of excess soil. Search through clean roots for the seed root at the base of the crown. Measure the root from where the seed was located to the base of the plant. Add ¾” to find seeding depth.

    Stalk

    This late into the year, the plant has used a considerable amount of nitrogen. If it’s not getting what it needs from the soil to fill the ear, it will start stealing from the stalk.

    “Look for cannibalization,” Beutke says. “Right now, you don’t want the first two to two and a half nodes to have a cottony pith.”

    The cottony pith means it’s weak and more susceptible to breakage, which makes for a slow harvest. If you find cannibalization this late into the season, there’s not much you can do. Make a plan for harvest, and consider prioritizing fields where you find cannibalization. Next year, reevaluate your nitrogen program to see if applying more fertilizer when the plant needs it might reduce stalk cannibalization.

    Ears

    Count out 1/1,000 of an acre. In 30” rows, this equates to a distance of 17’5”. Compare the total number of plants with the total number of harvestable ears. If you have 30,000 plants but only 28,000 ears per acre, you’re losing bushels. Examine the plant to see if it is a late emerger, has a nitrogen deficiency, is experiencing a spacing error or facing other issues that caused loss.

    It’s never good to discover yield loss, but checking ahead of time can help you set expectations and plan harvest order.

  • Scout for These 4 Corn Diseases

    Scout for These 4 Corn Diseases

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    As corn is at or near pollination across much of the corn growing states, it’s important to keep your crop focus on pollinating kernels. Scout for these four corn diseases to take action when possible and protect your bottom line.

    Northern Corn Leaf Blight

    Northern corn leaf blight favors mild temperatures from 65° F to 89° F. Fungal spores overwinter in corn residue. Next year, select resistant hybrids to reduce the likelihood of developing this disease.

    Northern corn leaf blight has spread from Minnesota to Tennessee and is one of the most common corn diseases.

    Warning signs and management tips:

    • Corn on corn fields and no-till with a history of the disease are more likely to develop the disease again this year
    • Cigar-shaped tan to gray lesions start on lower leaves and work their way to the top leaves
    • If resistant plants show infection they lesions will appear with yellow, transparent, irregular borders and fewer spores
    • Scout at or after silking during warm, wet conditions
    • Fungicides can slow the infection

    Gray Leaf Spot

    From corn silking to maturity watch for warm, humid weather to encourage gray leaf spot. The disease overwinters in corn residue, but fungicide can slow the disease.

    Gray leaf spot not only limits the plant’s ability to photosynthesize, it also opens it up for more fungus and disease to enter the plant. Scout to catch this disease early.

    Warning signs and management tips:

    • Early symptoms show small yellow or tan spots with halos
    • Symptoms later appear as gray rectangular-shaped lesions up to 4” long and 1/8” wide with parallel edges
    • Lesions might appear in early July on lower leaves, but the disease is much stronger and spreads faster in late July and August
    • Use resistant hybrids, tillage and rotation to minimize disease since its soil-borne

    Goss’s Bacterial Wilt and Leaf Blight

    Goss’s wilt thrives in warm, humid conditions. If you’ve had Goss’s wilt in a field before, you might see it again this year from overwintered spores. Consider resistant hybrids next year.

    Fields will be more susceptible if corn has undergone stress from wind, hail, machinery damage or has infection from other diseases that open it up for Goss’s wilt.

    Warning signs and management tips:

    • Lesions appear gray, yellow or red striped with wavy margins following leaf veins that might contain dark, watery spots
    • After splitting the stalk you might see orange to brown bundles visible in vascular tissue which can cause stalk degradation
    • There is no in-season fungicide or other treatment available for Goss’s wilt
    • Look for damage near corn silking, but it can appear anytime from May to September

    Antracnose Leaf Blight and Stalk Rot


    Watch for this disease during warm, wet summers. Since it can infect both the leaves and the stalk make sure you’re scouting early for stressors such as insect, disease, high populations or nitrogen loss. Leaf symptoms appear in late April through July, and stalk rot appears from August to late October.

    Warning signs and management tips:

    • The disease overwinters in corn residue, select resistant hybrids to mitigate risk
    • Leaf blight shows ¼” to ½” round or oval lesions that might have small black specks in the center of the lesions; when humid, disease starts on lower leaves and works up to the top leaves
    • Dark brown to black stalk lesions go through the rind
    • After tasseling, infection might cause the top leave the corn plants to die prematurely