Growers are encouraged to maintain planned soybean varieties despite expected planting delays due to the wet spring now being experienced throughout Northern and Central Illinois.

It’s critical to understand that a soybean plant is a “short-day” plant (flowering occurs when the day length becomes shorter and the plant is at least 14 days mature). The soybean varieties adapted to northern latitudes i.e. Group I or II, that are moved south, will flower too early.

It is NOT desirable for a soybean plant to flower prior to the summer solstice (June 21st) because soybeans require repeated exposure to short days for maximum flowering. If flowering begins prior to the summer solstice, the number of cycles to produce flowers is limited. In other words, the long days which follow the short days prior to June 21st result in decreased flower production (Source: Fred Below-Crop Sciences 518 “Crop Growth & Development).  Knowing that pod set occurs at each flowering point, it is obvious that more flowers provides potential for more pod set (higher yield potential) and vice versa.

Adjustments a grower should consider would be to plant the crop in narrow rows, and at a 10 to 20 percent higher-than-normal rate. These practices are recommended because later planted soybeans remain shorter and have fewer pods and seeds per plant than the earlier planted soybeans of the same variety. Use of narrower rows and a slightly higher seeding rate increases the plant’s growth efficiency, resulting in more pods per acre and reduced weed competition (Source: “Soybean Replant Decisions” Iowa State University Extension Publication).

During the last 10 days of April, flights of Black Cutworm Moths were reported from agronomists and extension specialists in various areas of Illinois, specifically southern Illinois. This indicates the migratory movement is now in progress and further movement north is anticipated. As weather patterns bring moisture up from the south, these same wind currents also bring black cutworm moths. Here are a few keys to scouting and identifying black cutworms as well identifying signs of injury.
 
The female cutworm moth migrates into Illinois by being blown in by winds and storms from the southwest. The females deposit their eggs in various hot spots, such as low spots in fields, overflow ground, and in areas that have dense grasses or winter annual weed populations.
 
These hotspots should give you a good indication of areas that you should scout in first. Other factors that favor black cutworm infestations are fields that were tilled and planted late, reduced tillage, and fields that are next to permanent vegetation. Also, rotated corn fields tend to have outbreaks more so than corn after corn.
 
Black cutworms can range in color from light gray to black and have a shiny and/or greasy appearance. At full growth, the Black Cutworm is about 1.5 inches long. Early cutworm feeding is commonly termed as pinhole feeding, because of the small and irregular holes in the leaves of corn plants. Pinhole feeding is a good early warning sign of potential cutting damage yet to come. Most cutworms actually cut the plants during the night, and feed on the plants during the day in a below ground burrow.

Corn is most susceptible to damage until it reaches about 15 inches in height. A cut plant will usually be severed just below the soil surface. The real potential for economic damage occurs when corn reaches the V5 growth stage and the growing point is starting to emerge above the soil surface. If a corn plant is cut below the growing point, it will not re-grow and recover.

Mike Gray and Kevin Steffey of the University of Illinois commented in the IPM newsletter “The Bulletin” that “Although the use of Bt corn hybrids, insecticidal seed treatments, and soil insecticides has made black cutworms less of an economic threat over the past several years, this pest's presence before corn planting suggests that a review of black cutworm identification, biology, and injury may be in order.”

We can use Growing Degree Day calculations to better predict when cutting may occur. We should begin scouting before we have accumulated about 300 heat units after an intense flight. A post-emergence rescue treatment may be necessary if three percent or more of the plants are cut and larvae are still present, particularly if they are less than 3/4” in length. If more than five percent of the plants are cut, then insecticide should be applied.

There are several insecticides that are labeled for black cutworm. Please consult with your local retailer if you have any questions or concerns.

Wet conditions have resulted in delayed corn planting throughout Illinois. Growers are concerned about delayed planting because corn planted after May 15th usually results in less yield and higher moisture.

However, it’s best to stay with longer season hybrids since they tend to yield more than shorter season hybrids. Why? Because fuller season hybrids are able to accumulate more dry matter resulting in better yields.

Plus, researchers have identified that hybrids tend to compensate their required Growing Degree Days when planted later in the season.

More important than planting date is the V10-V17 stage. This stage is possibly more critical than planting date because the corn plant is finalizing kernel number and ear size.

The longer the length of time available for kernel number and ear size development, the higher the yield potential. Earlier maturing hybrids generally progress through these stages more quickly thereby limiting their yield potential. Thus, if early maturing hybrids are planted, higher populations are required to produce comparable number of kernels.

Keep in mind that stress at silking is the biggest yield loss factor for the corn plant and planting a short season hybrid will not change that from happening.

Kernel weight may be reduced with an early frost, not to mention higher moisture, but, presumably, most growers have already selected a hybrid that would reach black layer three weeks prior to the average frost. By accumulating average to above heat units, the corn plant should reach physiological maturity as expected.

In summary, stay with your full season hybrid until May 25th, then shift back five days in maturity. For additional 10 day delay in planting, shift back another five days in maturity. Until then, maintain your previously selected hybrid. 

Cool, wet weather in central Iowa has brought things to a standstill this week.  The 3+ inches of rain we got last weekend put everybody out of the field, and then another shot of moisture last night.  This morning it is cool and very foggy--not very promising.

Still, I have to say that we're better off than most.  Conditions last week were good enough for at least four days in the field which really made a big difference.  Here on the Stine farm, we have most of the field corn planted and our seed production male rows are in.  We have some time before the female rows need to be planted, so for now there's no need to raise the alarm bells...yet.

Few topics in production agriculture today receive more press, and more discussion, than planting populations.  Yet for all the hoopla, a recent survey found that half of all corn growers have not changed their corn seeding rate in the past five years.

Why do growers not want to increase populations?  One answer might be a 'if-it-ain't-broke-don't-fix-it" approach.  Another reason might be an old notion about higher populations leading to stalk and standability issues.  Another limiting factor might also be the increased cost of seed inputs today.

Why should growers consider increasing plant populations? During the past 75 years, the national average corn yield has quadrupled.  How did that happen?  The answer, of course, is that the national average planting population has also quadrupled, allowing growers to put put more plants--and subsequently more ears--on each acre.  And along the way, technology and breeding has led to plants that can perform well at higher populations than their predecessors.

At field days and winter meetings, our agronomists spend a lot of time talking to growers about the importance of evaluating their corn planting populations to make sure they are taking advantage of the full power of today's newest genetics.  To be sure, today's genetics sold are not the same as they were 20, 10, or even five years ago, so why should your planting population stay the same?

There's a great article over at agriculture.com that speaks to this issue, along with a short video featuring University of Illinois Extension agronomist Emerson Nafziger.  To view the article and video, click here.