The month of July is now here and it will be a big month for influencing how well our crops perform at harvest.
Before June 30, the crops in the state were generally looking good except for the waterholes that occupy many acres between northwest and southeast Iowa.
While those waterholes can be frustrating and tough to make productive, the causal excessive rainfall often more than makes up for the acres lost.
The big storm of the season, so far, happened last Monday. In the southern two-thirds of Iowa there were three to four storm lines that brought 3 to 5 inches of rain and winds that clocked at 60 to 80 mph.
Most people recognized there would be crop problems as a result, but that it would take several days to assess all of the damage. After a week what are people learning?
The first category is greensnap. This refers to the winds being strong and gusty enough to simply crack the stalks and break them about two feet above the ground.
I am hearing reports of 20 percent breakage in fields and have seen fields where six out of eight consecutive plants were snapped off. Those plants may live until fall, but will not produce any ears.
The sad observation made over the years is that it is often the strongest stalked hybrids that have a green snap problem as they are less flexible, and don’t whip as will a more flexible stalk.
It was more of a problem this season because the plants grew too fast once the weather warmed. A field observer from southeast Iowa was keeping close tabs on corn plant height by placing graduated stakes in his fields.
During one 10-day time period he measured 30 inches of growth. Those plants likely had not hardened off the stalks yet.
There were quite a few fields where the plants were blown over, and, in cases, laid the plants almost flat. At times we see the plants push out new roots and push themselves upright. The plants have done a partial job of correcting their lodging angle. Some are still tipped, but are resuming their upward growth.
The problem is the lodging leaves the lower parts of the plants about 20 to 30 inches away from being vertical. That makes any further field traffic impossible on north-south rows.
Though the eastern Nebraska storm did not generate as much publicity in Iowa, their crops got hammered by large hail, strong winds, and flooding conditions.
Besides the uncertainty of knowing what to do to maximize crop recovery, they also had to make decisions based on whether to replant with corn on the speculative information as to when, and if, their center pivots could be repaired or replaced by the irrigation kick-off date.
What new corn disease has become a major threat to corn production and has forced everyone attempting to raise profitable corn yields to pay utmost attention to what the ratings are for their favorite hybrids?
In case you had not answered Goss’ wilt, the least mentioned corn disease in the Midwest, or that it could explode after a hard rainstorm, where the leaves were roughed up, it is time to recognize that we could find the disease in its moderately early stages in every field.
It was in every field last year so this was inevitable. It loves moist weather and temperature does not seem to affect it much. After getting into the fields again after the long and somewhat wet weekend, the disease is easy to spot on a high percentage of the leaves now, rather than just on the lower stalk.
Those lower lesions seem to be growing into the stalk, where they like to choke the movement of moisture and nutrients moving up the plant’s plumbing tissue. The end result of this has been bad since 2010.
Now might be the time to be proactive and follow through on your Goss’ wilt response plan. Even if corn is going to be priced at $4, $4.50, or $5 per bushel, producing versus not losing those 45 bushels that have been gained by treating the bacterial disease can make a huge financial impact on your operation.
CRW, other insects
By now every farmer growing second-year corn should have ventured into their fields to gauge the amount of feeding pressure on the roots. Thus far the Herculex trait did a decent job, but still showed a small degree of feeding.
Only time will tell how long the egg hatch will continue. With last year’s dry weather and deep-soil cracking there would have been CRW eggs laid deep in the soil. Those could continue hatching for another few weeks and likely generate the late feeding and beetle flights that were numerous in parts of northern Iowa.
At this time last year the hordes of Japanese beetles were devouring leaves off many different plants. They appeared and fed by the thousands.
While one or two appeared several weeks ago, there has not been any big invasion of any town or county across the state. At least the cold winter was good for insect control of some species.
Lots of press is now being given to the so called super weeds. While they aren’t faster than a locomotive or bigger than a locomotive, as Palmer amaranth is supposed to be, the potential competition from the 10, 50, or 200 one-quarter-inch tall waterhemp plants found in many fields is scary.
As they grow and grab their share of moisture and sunlight they can do just as much damage as bigger weeds unless a good weed management program is used as soon as the ground dries up.
The current best management practices is to use overlapping residual herbicides that are applied before seed germination, and then reinforced with a newer application generally made around the V4 growth stage.
In that manner there is never an unprotected time period where weed seeds and young seedlings have an opening in which they are unchallenged by some weed protection product.
One management practice on soybeans what was demonstrated at a Nebraska cover crop field day was when the farmer left his cereal rye reaching the heading stage, when he then crimped it which was fatal to the plants. He then had a vegetative mat into which he could plant soybeans.
That mat allowed the allelopathic compounds in the straw to eliminate weed competition.
There is also a line of introspective thought that has been captured in several weed management guidebooks. That line encourages the growers to give thought as to what soil and mineral properties are in place, or lacking, that the presence of the weed is trying to solve.
If compaction brings on grass germination or a lack of enough boron fosters a certain group of weeds to appear, then remineralizing the soil or adding calcium or Ca or calcium sulfate may be a better management strategy.
We are hearing more about how many operators have gone back to the practice of mixing five to eight herbicides into one tank in an effort to have the entire weed spectrum for that field covered.
That is just how it was done 15 to 20 years ago. In another month we will be able to learn how well each product or tank mixed worked in different areas and under specific weed pressures.
The annual conference of the U.S. Phytopath Society is being held in mid-August in Minneapolis. It looks like they have played catch up enough to recognize what many farmers have already recognized and read about.
During the Monday session there are three well-known researchers who will be presenting on soil health and sustainable farming practices and how they related to plant/human health and nutritional productive systems.
They will also be talking about the soil microbial effect on plant health and growth with emphasis on how it affects human health and food security.
Bob Streit is an independent crop consultant and columnist for Farm News. He can be reached at (515) 709-0143.
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