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By Staff | Jun 18, 2018

The early part of the growing season is getting closer to ending for the growers in central and southern Iowa. Though there is no clear definition of what it the early part of the season, it can be considered the time after planting to when tractor traffic through the corn fields is coming to an end and any more passes would be with high clearance machinery or aerial passes.

Three weeks ago when a high percentage of the corn was finally getting planted or was finally emerging many of us had our eyes on the calendar and figured there was no way we would have knee high corn by the 4th of June, as has been happening in recent years when field work was beginning the second week of April.

Since then we went from the coldest and snowiest April on record to the warmest and one of the driest on record. A long string of days where temps were in the high 80s to high 90s, which led to one of the most rapid GDU accumulations has given up phenomenal corn growth and many fields across the state are getting close to or at V6 when row closure is only about a week away.

Soybean plants and progress is a different story as a high percentage of them were planted later than normal. With them being a C3 plant they simply do not respond as much to warmer weather. Therefore the ones furthest developed are still in the V3 to early V4 growth stage. The majority, even those that were planted in April are still at V3. In my trek up to extreme northwest Iowa this week it was astounding to see such a high percentage of the soybean acres and fields as being just planted or only recently emerged. Plus there were scattered fields with drainage problems where the ground was still too wet to work and had not been touched.

So in this last week for the tallest corn fields it will be important to pay attention to those showing signs of yellowing due to loss of N, lack of sufficient sulfur, or general lack of minerals such as Mn, Bo, Zn or Moly that would still need to be verified thru tissue testing with follow-up foliar applications. Now is when last minute management can be very important as to which fields will surprise this fall and which ones may disappoint.

Early disease management

Proper disease management likely begins with establishing decent water drainage for each field. Having low oxygen, saturated soils create an environment where roots have a tough time growing and the slime mold fungi flourish. These would include Pythium, Phytophthora, Rhizoctonia and Fusarium that can cause early season damping off or establishment of fungal populations that can harm or kill plants later in the season. Having every field pattern tiled is only a pipe dream for many operators. Often lack of decent fall and flow in local streams to move the water away is a limiting factor for many operators.

After drainage the next big item is establishing healthy plants is keeping tabs on and maintaining high mineral levels in the plants. Lack of the major micros leaves the plant immune systems operating as less than peak efficiencies. Plants are somewhat like cars and trucks. The better they are maintained and nourished, the better they run and perform.

In university trials where different fungicides and rates are applied during the early V stages, getting a good and consistent return on investment from them has been difficult. Sound nutrition typically pays dividends as it influences yields so much as well as helping to moderate or eliminate pathogen problems.

Planter innovations

A number of farmers I work with spent time and money making additions to their planter to allow for better seed spacing, higher speeds, along with better depth control and seed placement with hydraulic down pressure systems. After scouting those fields I have to say I was impressed. The stands have improved in plant counts and evenness of emergence and growth. Belt intactness and longevity will be an issue and will need to be monitored to keep the planters operating at peak efficiency. In most cases spending the money to make the retrofits on an otherwise sound planter made sense. We will see if extra bushels are generated at harvest to pay for the changes.

Insects and the search for perfection

With many of the corn acres as the V6 growth stage arrives or nears one insect that typically appears on the plants in the outside three or four rows is the common stalk borer. The moth lays its eggs in the grass alongside the field and after hatching the larvae move into those rows, crawls up the plant and then down into the whorl, where it eats out the growing point. Growers who insist on preventing lost bushels will make one pass with their sprayers to apply a long lasting insecticide to prevent damage from the CSB and its colorful larvae.

2017 was supposed to be a peak year for the European corn borer populations and the damage potential in corn fields. The peaks and valleys of years ago were believed to track closely with the ECB populations and two natural enemies, one a fungus and one a bacterium. In NW Iowa the populations proved to be high and were a concern on conventional corn hybrids. Well, don’t look now but the light trap counts from the UNL research station at Concord, NE so far are telling that the of a number of different moth species, including ECB, are on the rise. Pay attention to them if you have conventional hybrids.

Nematode news

There appears to be a coordinated effort to raise awareness of the yield loss that soybean and corn nematodes are causing in our crops. The north central part of the state is the most heavily infected as their fields are likely getting continually reinfested by ducks and black bird carriers winging their way north after they pick up the small worms in the Mississippi Delta. Now that the Fayette does not seem to be as effective as it was 20 years ago and new plant introduction sources must come thru the Chinese State Dept, developing new and affordable methods of control will be important. We are still placing some plots where we will be testing four new, including three EPA registered nematicides with two that can be applied post emerge. Review papers and test results versus other hard chemistries such as Telone are reporting of superior results from the O2’s use. The Chitosan mode of action is unique.

That generates a question from many farmers. And that is are we losing corn yield to nematode attack by species that attack corn? Glenn Dappan, of Nema Test in Lincoln, NE, who teaches science at Dakota Wesleyan does nematode ID and count work for several soil testing and seed companies in the Midwest. In visiting with him last week he is finding fairly high counts on lighter OM and sandier soils in central and western NE. Their main species include the Needle (Xiphinema), Lance, Lesion (Pratylenchus) and Stunt types. Because they are not very mobile they are more prevalent in sandier soils. He estimated that with the higher populations he is detecting some of those fields the operator is losing 5 to 15 percent of the projected yield.

Concurrently I was visiting with a very knowledgeable irrigated corn grower south of Muscatine on the Illinois side. He is battling very high counts of several species. The only registered product he can use that is affordable is Counter. Its use eliminates the ability to use some of the best broadleaf herbicides in corn, so he is handicapped in trying to manage the pest.

Plant health

When the tallest corn grows into the V8 growth stage later this week and V10 the following week corn growers need to start watching for the small caramel colored lesions moving from the ground up. If what has happened since 2009 repeats itself this bacterial infected will cause the plants to die early. That will be the time to apply the BioEmpruv and Argosy to boost plant health enough to fight off the attack.

Weed control in soybeans

While the soybean plants seem very slow in adding new leaf stages the broadleaf weeds that are competing with them are growing very rapidly and could be tougher to control after they reach 4 inches in height. In reading the labels most recommend not applying Flexstar until after the V1 to V2 growth stage and while the weeds are less than 4 inches in height. In cases where the bean plants were being shadowed by taller water hemp, growers and custom applicators were asking if earlier applications were allowed, as in the unifoliate growth stage. As most of labels read, once the first unifoliate stage is reached, Flexstar can be applied. You don’t want any waterhemp to form the side branches, which making them tougher to control.

Air inversions

As I was working and traveling last week I had the chance to be around fires on five of the days right around sunset. I was watching the smoke to see if there was an air inversion during those mostly 90-plus degree days. All five of them had the smoke rise a short distance and them move sideways. Be aware of these inversions since this is when vapor drifts are most likely to occur.

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

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