No matter when your corn was planted, one thing holds true. It needs to be scouted, and perhaps this year more than ever. Warm, moist conditions set crops up for diseases. Widespread planting dates and late-planted corn in an area may impact which insect pests you see where.
Dave Nanda, director of genetics for Seed Genetics-Direct, advises grabbing a scouting book or your cellphone with an app and heading to the field. One quality resource with pictures of things you might see is the Purdue University Corn and Soybean Field Guide.
Nanda says what you will find often falls into these categories:
Normal growth stages. You can stage corn by counting leaves. Nanda prefers the method that counts the uppermost leaf with a collar as the final leaf to count. Knowing growth stage can help you make determinations as to when the growing point is above ground, and in some cases, if it’s still OK to make postemergence herbicide applications. You can also take stand counts at this point. In some cases, you can get a handle on planter performance based on stand counts and plant spacing.
Unusual growth patterns of little consequence. Sometimes a plant shows striping or some other symptom, and it’s the only plant showing that symptom. Occasionally, there’s an important cause, but often it’s just a quirk of nature. Remember, if you’re planting refuge-in-a-bag corn with a second hybrid included because a GMO insect trait is included in the main hybrid, you may see the occasional plant that looks slightly different from other plants.
Signs of nutrient shortages or disease. If you find plants showing classic signs of nutrient shortage, such as purpling, which is usually indicative of a phosphorus deficiency, it may or may not be important. Sometimes these are situational deficiencies, Nanda says, caused by weather conditions. The plant is truly short on phosphorus, but as soon as weather conditions improve, the deficiency will disappear. Purpling doesn’t always mean there is a true deficiency in the soil.
Disease lesions can appear relatively early. The sooner they appear, the more likely the disease could cause economic harm later. Note disease lesions and plan to scout regularly to monitor development.
Nanda’s best advice is to walk fields and pay attention. Try to explain as many potential problems as you can and figure out why you’re seeing what you’re seeing. This may help you make management adjustments for next season, even if it’s something you can’t correct this year.
Check out the slideshow to see photos of these situations.
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<p>Every snapshot you see in your mind’s eye walking cornfields tells a story. Note the soil erosion and gully that formed after planting. This could be a common sight this year.</p>
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<p>In addition to a pocket guide, take a rope with stakes marked for various row lengths to take stand counts at various places throughout the field. It’s more accurate than just stepping off 17 feet, 5 inches for 30-inch rows and guessing, Dave Nanda says.</p>
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<p>Dave Nanda counts plants along the rope stretched out to represent 1/1,000 of an acre. He counts plants in rows on each side of the rope, and then averages the two numbers to get a count for that location. If he finds 30 in one row and 32 in the other, his acreage for that one location is 32, or 31,000 plants per acre. He repeats this at other locations. Note the plants behind Nanda. Leaves are ragged and torn. This field was hit by two minor hailstorms days apart at about the four-leaf stage. The plants grew out of the damage and produced top yield.</p>
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<p>These leaves are ragged. This is the same field hit by hail shown in the previous photo. Since the growing point wasn’t above ground yet when the damage occurred, most plants regrew normally. Look at the plant on the left. Notice the set of yellowish marks with tiny holes on a leaf extending to the left from the whorl. “At first glance it resembled shot-hole feeding from corn borer,” Dave Nanda says. But he determined it was too early for corn borer feeding in this case. “When we looked closer, what we were really seeing were like stretch marks where the leaf came out of the whorl. Corn was growing so fast during that period in May in 2018 that it apparently produced those marks.”</p>
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<p>Sometimes you will find a plant that isn’t doing as well as its neighbors. In this case, the farmer suspected there was some anhydrous burn from the ammonia he applied several days before planting. Only a few plants seemed affected, shorter and a bit pale. Dave Nanda dug up this plant and confirmed that root growth was minimal. Roots could have been damaged by being near the anhydrous band, although it’s not the only possible cause.</p>
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<p>Here is a spot with a gap in a row. On either side, corn plants seem closer together. Was it a planter malfunction? If you only find this once, it’s not a large concern. If you see it repeated across the field, you may want to return to your planter and try to figure out what was causing it, Dave Nanda says.</p>
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<p>This leaf with an unusual pattern is in the same field hit by hail where the plants with shot-hole-like symptoms attributed to fast growth were found. This photo was taken about three weeks later. Dave Nanda believes the pattern on this leaf formed when the leaf emerged from the whorl during a super-fast growth period. It’s something to note, but not to worry about, he says. It’s not a disease lesion and won’t have any consequences.</p>