Corn breeders and agronomists have emphasized for years that if corn plants don’t emerge together, late emergers contribute less to yield. Sometimes they are so far behind that they turn into weeds, robbing other plants of precious nutrients and water while contributing very little to yield.
However, that doesn’t totally explain the differences in this photo. The plants by the pink flags are significantly taller than the plants by the white flags, even though they all emerged within 24 hours of each other. The two plants in the middle, by the yellow flags, emerged three to four days after the pink-flag plants and are not only shorter, but also one-half growth stage behind.
“The environment in the field plays a role not only in emergence timing, but in what happens to plants after emergence,” says Steve Gauck, Greensburg, Ind., a regional agronomy manager with Beck’s and a farmer himself. “It can be tied to something as basic as a difference in seeding depth, even though the row unit was set to drop at a uniform depth. There is lots of variation in the natural environment, which can lead to variation in how plants respond.
“Soil fertility in the zone around each plant can differ. Plus, soil compaction can vary from spot to spot, even within a row. It can have a very large impact.”
Closer look at crop production
Matt Montgomery, agronomic education lead for Beck’s, Chatham, Ill., breaks crop production down into three pieces:
- starting the crop off right
- keeping the crop right in-season
- ending the season right
“The chain has three links, and if you hamper that start, the possibilities for yield are reduced for every link in the chain thereafter,” Montgomery says. “Uniform emergence matters for that right start, but it is not the only consideration. If we delay planting in pursuit of rapid, uniform emergence, we risk substantial planting delays. Delayed planting has a direct impact on how variable yield outcome will be.”
He notes that early-planted crops tend to have highs and lows for final yield that are much closer together than later-planted crops, which can see dramatic yield differences. Yes, planting date strongly influences final yield, and earlier planting should be considered as much as possible, but only when soil conditions allow, Montgomery emphasizes.
“Anything that restricts root development, like soil compaction, trims the plant’s ability to scavenge the soil profile for moisture,” he explains. “This means less drought stress resilience and more chance of reduced yields. Constricted root development from soil compaction impacts the plant’s ability to secure nutrients.”
Plant nutrition based on nutrients in the microclimate around the plant, seeding rate and correct hybrid placement all factor into the outcome. They may not fully explain why one plant is taller than another in the same row, but they are contributing factors.
“A plan for product placement is imperative and must be followed,” Montgomery says. “A crop plan isn’t just pulling a product from the shelf and planting it in any field.”
Japanese beetles active in Midwest
Assessing the start for this year’s crop and watching out for signs of tar spot aren’t the only two tasks for those scouting fields right now. Insects are also making an appearance in various locations. Japanese beetles have captured attention in Iowa recently.
“Finding the first Japanese beetle each June is a point of pride for some, including folks in my lab,” Erin Hodgson wrote in a report featured in a recent Iowa State University Extension Integrated Pest Management newsletter. “They found adults in corn this week. Hurrah!?” After checking accumulating growing degree days for 2025, Hodgson confirmed that beetles appeared right on schedule and were likely emerging across the state.
She notes that Japanese beetles need about 1,030 growing degree days, using the base 50-degree-F system, to complete development. Emergence will continue until around 2,150 GDDs accumulate. That means the insects will be around for several weeks.
Why should you care? Based on information in a journal article that Hodgson co-authored, the biggest threat to corn is if Japanese beetles are numerous enough to clip silks. Leaf feeding by these beetles can occur but usually does not reach economic levels.
Silk clipping, however, can be a problem. The article notes that the first five days of silking are most critical. If silks are clipped during that time frame, blank kernels could result. Other insects also can clip silks, including adult rootworm beetles.
Authors of this article recommend scouting during silking and pollination. Here is their recommendation if beetles are active, clipping silks. A foliar insecticide is warranted if three conditions are met:
- three or more beetles per ear
- silks clipped to less than a half inch
- pollination less than 50% complete
Recommendations may vary slightly state to state. According to the Purdue Corn and Soybean Field Guide: “The economic threshold is reached if silks are cut off to less than a half inch before 50% pollination, with beetles present and actively feeding.”
Find the full ISU-based journal article online.