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By Staff | Sep 23, 2011

Now after preparing for, planting, fertilizing and keeping the crop weed free for as much of the season as possible, then trying to manage the diseases, we are at the cusp of finding out how well we did.

Even at the start of the season it seemed that nothing about the crop was going to be easy – we would have to fight for every little advantage.

The SDS invasion of 2010 season taught growers in cruel fashion that what they could not see and did not fully understand could hurt them severely.

This year we learned a few more lessons including insects, weeds and diseases were going to continue to be tough opponents.

Many of the first two have shown evolution-wise that they have always been quite adaptable to selective pressures placed against them. They are likely to be around long after we are gone.

It appears that we might be the ones who have to adapt and not them.

Combines are beginning to roll in a few surrounding states and a few yield checks have been made.

Only a few have been publicized, and the trend so far repeats the old rule that heavy ground can still yield well in dry years.

There will be bad yields, some ranging from disappointing to decent and some will be surprisingly good. So far the operators have not been broadcasting their news over call-in shows, neighborhood gatherings or web sites.

Some because the yields are low, while others will keep quiet so as to not sound like they are bragging. This was an expensive crop to plant and take care of, and growers are just hoping that most of their fields will meet expectations.

The frost

Quite a few meteorologists peered into mid-September and noticed the new moon, thinking that it may signify a chance of frost.

Those cold temps moved across parts of northern and central Iowa to affect the crop, with the degree of damage depending on location, topography, planting date and maturity of the crop.

We know enough to state that it requires about four hours at 28 degrees to kill a crop and less than that will burn off the top of both corn and beans. It typically takes a second cold night to kill both crops.

What is visible with the bean crop is that the cold night froze the top 6 to 10 inches of the canopy, leaving the middle and lower leaves and stems alive to help plump up the seed size and finish the pod fill.

Losing the top leaves is bound to skin a few bushels from the final yields on the later maturity beans, but won’t hurt the earlier beans unless they were planted late.

One should open a few pods to see if the seeds have begun to turn yellow and if the integument tissue has separated from the seed and pod. If it has, the seed should end up yellow and round rather than greenish and lima bean shaped.

A higher percentage of the corn fields were already brown and dead due to disease, thus the Sept 12 frost won’t be an issue for them. Their lower yields are already written in stone.

Those that were still green and alive did need more time. Having the middle leaves and stalks still alive will be important as they try to fill the seeds over the next two to three weeks.

Corn crop appearance

Just a short five years ago the plants stayed green until the last two weeks of September if the person was planting adapted varieties.

By having the normal 55 to 60 days from silking to black layering, the plants were able to form the normal amount of photosynthates and fill the kernels as deep as possible.

This year keeping each field and each variety green proved very difficult for many growers and agronomists. We thought we had things figured out and fungicides were going to be the answer. But that has not proven to be the case.

Now we need to develop new answers as to why old diseases, such as, Goss’s wilt, have suddenly become virulent and spread across the Corn Belt, and why new “chimera” diseases are now appearing.

That term arose in Greek mythology where parts of different animals were mixed to form a new creature. Right now electron and light microscope examinations are verifying the occurrence of new combo diseases on our major crops.

This is the case in parts of western Iowa where erwinia stalk rot seems to be nailing hybrids that are rated as resistant to Goss’s bacterial infection.

The condition of the corn crop nationally was downgraded again recently. That was no surprise except it was happening in the major states like Illinois and Iowa.

When the USDA and Pro Farmer surveys were conducted, all the participants were able to do was guess what the fields would yield if conditions returned to normal from that point on and grain fill returned to normal.

But normal didn’t happen, and they could not accurately guess how well or poorly the final months of the season would end.

The rain that arrived a week or two ago helped the beans greatly, but was too late for much of the corn.

The harvest has begun in different parts of the state. Expect to hear varied results depending on soil types, rainfall patterns, hybrid characteristics, herbicide use and the application of any foliar fertilizers.

I have heard of corn yields in Iowa as low as 50 bushels per acre at 30 percnet moisture and as high as 220 bpa at moistures in the mid-teens.

Based on what we have been seeing in fields in central and north central parts of the state, there will be many producing yields in the 150 to 175 bpa and some slightly above 200.

That will be below the genetic capacity of 230 to 250 that many are capable of producing.

Where plant death was very premature, yields may be more similar to those in Illinois where 105 to 130 bpa yields are common.

Remember the early- to mid-summer plant appearance where the light green/dark green streaking of nutrient deficiencies were present in about 95 percent of the fields?

This was ignored by most people. The effect of doing nothing rather than responding to remedy the situation will be seen in the grain tank.

One thing that we have been seeing is pinkish colored, dead corn and bean plants in diseased fields.

Pink or red normally mean fusarium which can signify mycotoxins.

We are hearing from many scouts and growers that they have coughs, blurry vision, cold-like symptoms and chills after walking through such fields.

We are sending plant samples to a top toxicologist to see what might be present and to learn of any precautions that might need to be taken by the harvest crews.

More storm damage

After touring parts of northern Iowa, it is evident that there will is a risk of significant field loss from severe stalk lodging.

There have been several concentrated wind storms that moved across the northern counties.

Many fields look like they have been steamrolled with few stalks remaining upright. Thus far, operators have been getting through the worst of the downed 30 percent moisture corn at speeds around 1 mile per hour.

The soybean crop

In a year where all overspray areas were seen as yellow flashing that lasted the rest of the season, we expected the appearance of bean diseases.

In parts of the state, SDS is present at levels that will affect yields. One uncommon disease that became recognizable about three weeks ago when large oval-shaped areas of bean plants turned brown.

A close examination and root dig didn’t match SDS symptomology, but dark spots on the leaves and black hairs on the leaves along pod lesions matched the description for foliar anthracnose.

While low levels of stem anthracnose is present annually in all fields, seeing it attack the foliage and do damage is unusual. In drier parts of the state, charcoal rot has been verified.

Dryness, stalk quality

Dead stalks tend to lose their strength within a few weeks after senescence, especially if any of the stalk-rotting bacteria and fungi are present.

The same can happen when and if the stalks get so dry that they lose their turgor pressure. The combination seems to be at work in southeastern and north central Iowa where those conditions are present.

So while it would be nice to let the crop field dry to 13 or 15 percent moisture, that may allow too much field loss to occur.

Heed advice and scout your fields to identify those with potential stalk problems.

Residue management

Most informal surveys still show that Iowa producers would like to increase second-year corn acres to respond to the price ratio that favors corn and to grow their own feed.

That means learning how to manage the residue so it decomposes to release the captured nutrients and allow a die-off of the disease inoculant while still protecting against soil erosion is vital.

One of the interesting things going into harvest will be to see how well the products that were meant to boost plant health and minimize the effects of the bacteria on yields worked.

Thus far, the majority of the sprayed fields lost their sliminess and stink and the disease seemed to subside. Most are still green and look better than neighboring fields.

Several that were treated were possibly too far gone to bring back, but if it is your field that was worth $1,400 or more per acre, don’t you have the right to try to save it?

Next year, everyone needs to have an improved management plan in place to control the disease and to manage their weed and fertility situation that allowed the disease such a strong foothold.

Most farmers likely dismissed talk of the disease as they had not worked with it before or seen firsthand what it could do. Most still can’t identify the stalk phase of the disease.

There will be several very interesting findings released in upcoming months that will suggest that changes in are in store for corn growers.

None of those will be patentable so the shift will have to happen at the grassroots level.

Bob Streit is an independent crop consultant and columnist for Farm News. He can be reached at (515) 709-0143.

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