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By Staff | Sep 18, 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. At the start it seemed that nothing about the crop was going to be easy and 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 that 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 that have to adapt and not them.

Combines are beginning to roll in few surrounding states and a few yield checks have been made. Only a few have been publicized, and the trend if of disappoint yields. The operators are not broadcasting their news over call-in shows, neighborhood gatherings, or web sites, meaning that they are less than desired. This was an expensive crop to plant and take care of, and it will prove to be expensive if it does not met expectations.

The 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. Major variations in summertime rainfall and temperatures along with fertility and hybrid characteristics would affect the final grain fill.

This year keeping each field and each variety green proved very difficult for many growers and agronomists. They 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 the new answers as to why old disease such as Goss’s Wilt have suddenly become quite virulent and spread across the cornbelt and why new ‘chimera’ diseases are now appearing. Where that term arose is in Greek mythology where parts of different animals, such as the head of a lion or dragon were mixed with the center of a horse and the tails of a snake. 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. In cases a high percentage of the plants have already broken off.

The condition of the corn crop nationally was downgraded again recently. That was no surprise except it was happening in the major states such as Illinois and Iowa. When the major 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. They didn’t and could not accurately guess how well or poorly the final months of the season would end.. The rain that arrived a week or two helped the beans greatly, but was too late for much of the corn. While that 1 to 2 inch rain was great, it only supported 8 to 10 days of ET use.

The harvest has begun in different parts of the state. Expect widely varying 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 Bu/A at 30% moisture and as high as 200 Bu at moistures in the low 20s. Based on what we have been seeing in fields in central and north central parts of the state there will many producing yields in the 150 to 175 Bu/A 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 Bu/A 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% of the fields and was overlooked by most people. The effect of doing nothing to remedy the situation or responding 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 means mycotoxins. We are hearing from many scouts and growers that they have coughs, blurry vision, cold like symptoms, and chills after walking thru 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.

The Soybean Crop

In a year where all overspray areas were seen as yellow flashing that lasted the rest of the season, we had to expect the appearance of some bean diseases. In parts of the state SDS is present at levels that will affect yields. One strange disease that became highly visible about two weeks ago was where large, irregular, oval shaped areas of bean plants turned brown. A close examination and root dig didn’t show the symptomology of SDS, but dark spots on the leaves and black hairs on the leaves along with forming lesions on the pods matched the description of foliar Anthracnose. While stem Anthracnose is present at low levels in all fields, seeing it attack the foliage and do damage is unusual. If this is verified in the lab why has it elevated its virulence?

Dryness and 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% moisture, that may allow too much field loss to occur. The amount of lodging seen where the strong winds have gone thru in the past few weeks verifies that the potential for serious field losses is present. While the big July storm that blew through in mid-July got lots of publicity, the numerous small ones that affected other part of the state in the past three weeks may be just as severe but don’t cover as many acres.

Portions of northern Iowa have been pounded recently.

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. What does require work, planning and expense is a program where 20-30 # of nitrogen, 10-20 # of S, sugar and a microbe mix such as Z-Hume or BioCat is sprayed on the residue as soon after harvest as possible. Those mixtures can do a very good job though the weather at harvest determine how much of the work gets done.

Goss’s Treatment

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, 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 $1400 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. Now they need answers on what it is and why it attacking their crops. There will be several very interesting findings released in upcoming months that will a few changes in what needs to be done. None of those will be patentable so it will have to happen at the grassroots level.

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