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Crop watch

By Bob Streit - Columnist | Jul 20, 2021

Now that we have past the July 4th holiday weekend and the crop forecasters think they have good feel for the crop size of the corn and bean crops. On the producer side we recognize that what we consider normal with weather is not occurring in much of the Midwest. On July 5th we took a tour of the local area to see how the corn plants were doing. It was a hot and windy day, the leaves in many fields were rolled tight and many areas in many fields had the silver sheen of when they begin to give up the ghost. My thoughts were that if we did not get a substantial rain within seven days many of the fields were going to suffer substantial yield losses and some even totaling out. The first tassels began to poke out and moisture was so limited that the silks, which are 98% water, might not have enough to extend out the husk to meet the pollen that was starting to be shed.

Then out of the blue, and not in Erick Snodgrass’s or Simon Atkins’ predictions, a cool front from the northwest marched through generating rainfall of 1.5 to 5 inches over the next few days. This reprieve allowed both the corn and beans to recover, with both showing a growth spurt the following days. More regular rains are needed Midwest wide. With the corn crop needing .25″/day now the two-inch total for many areas will last just over a week. I saw rolling leaves during a Sunday drive up to Hampton.

Show and field days

There are a few items to put on the calendars. The fair season has arrived en mass and many families are fully employed with showing animals and or taking them to the auctions. It is a time when the dedicated work by kids showing calves and adults showing on their favorite breeds compete with fellow livestock men/women to earn their coveted purple ribbons. It is always a bittersweet moment when the animals they have cared for over many months get auctioned off and sent to the packing plant. Hats off to the many club leaders for their efforts to teach dedicated and hard work among kids in their formative years.

The show up at Baltic, South Dakota is scheduled for July 29th. There are usually a few tidbits of information that can be gleaned from attending. Two years ago when Dowdy spoke he answered an attendee’s question about micro-nutrient recommendations by each lab following tissue tests being run. He found that many testing labs were simply averaging the results from their previous season, and were not addressing the crop needs of those attempting to produce very high yields. Work at a testing lab in South Dakota helped high yield achievers work backwards from their final yields to correlate to what mineral levels let them achieve their high yields. They now have enough experience to give guidance. Average yield goals and tissue test levels tend to produce average yields. This reinforces the low stave theory.

Tissue testing and new high efficiency fertilizer

Tissue testing is the most direct way of gauging how much of your applied nutritional program was actually getting into the plants. At the same time many growers have been seeking the commercially available fertilizer that will give the best results of getting into the cells and showing up in subsequent tissue tests. This is where the amino acid chelated minerals and micronutrients appear to be setting new standards for moving the tissue test levels and giving good results when applied at low ounce rates. Remember that the most used fungicides of 40 years ago had Cu, Mn, Bo, Iron and Zi as their active ingredients. The Dithiocarbamate category carried human health warning labels, were short residual, and not systemic. These new mineral products have had those limitations removed.

In the many tissue test reports we are seeing lots of K deficiencies as well as general shortages of Mn, Mo, Moly, S and often zinc. Dry soils and lack of microbial activity are less likely to release those minerals. If those situations occur the optimum way to address the plant needs is through foliar applications or possibly through Y-drops. One set of tissue results actually had levels of .02 and .01 on the moly. At those levels soybeans may not nodulate, as Moly is crucial to the nod factor getting activated.

The corn crop

People are asking if the top end of the corn crop has been hurt. There is a website that actually tallies the stress degree days accumulated so far that summer. Early in the season the plants can tolerate tough conditions. Nearly every day in June 2021 accumulated stress hours. Near tasseling time the plants are less able to tolerate stress and yield losses can become substantial. There were fields that were barely 4.5 feet tall that were starting to tassel. Ear size could be reduced quite a bit. The next two weeks will be crucial to the corn crop in parts of the state as the kernels will only reach the blister stage and prone to aborting a few to many rings of kernels.

Strong winds accompanied the rains in many areas. Many fields of second year corn that had CRW damage had not grown recovery roots showed varying degrees of root lodging. In a dry year losing a major percentage of their roots can affect yield significantly. At that stage of development they typically do not push themselves upright anymore. We have seen hormone-based products and biologicals plus mineral packages sometimes help the plants revive and right themselves if they get rain to aid the effort.

Questions have risen about any new methods of controlling CRW. One what was tested in the state using Corn Grower funds was a program where they used Cornell’s beneficial nematodes to consume SCN eggs and juveniles.

Work done last year by a team of seed people was devoted to seeing if Steward insecticide would work as a post emerge applied insecticide that was effective against feeding larvae. Because it is labeled as a long residual beetle controlling product, when it was tested locally the results were promising.

In the early 2000 a CRW control program originating from a team of Beltsville, MD entomologists who discovered a genetic throwback watermelon that tasted extremely bitter. When Jerry and Tom Brown of Florida Food Products of Eustis, FL processed the melon juice into an emulsified concentrate. Using ground driven or aerial equipment corn growers were able to window each field and spray alternative strips with the juice mixed with a low rate of a labeled insecticide. They eliminated 20 days of beetles and their egg laying with each application. It worked like a charm. We’re hoping the Invite program can be revived and are working to make that happen. The Chrome is proved effective in heavy pressure fields.

Soil N tests

During the driest spring and early summer period ever, it was logical that no leaching of N occurred. Soil and stalk test levels were very high. That is likely part of the reason the pigweed pressure was severe in most fields. University research has documented that for each day with a soil temp above 50 F, 5% of the N could be lost to leaching or denitrification. Without a corresponding level of Moly this N will not be utilized as it should be.

Leaf diseases

Until lately there have been very few disease lesions showing up on the corn leaves. Just this past week the first faint Eyespot lesions could be spotted on the upper leaves. Days with dews that keep the leaves wet through mid-morning dews. The first common rust lessons were seen as very small reddish leaf eruptions. As to guidance on how to manage the crop a good tidbit was passed on by John Kempf in his recent column. He learned this from Dr. Bruce Tainio, a very wise plant scientist from Spokane, WA.. Bruce and John advise testing for sap pH and monitoring the ratio of Ca to K to monitor the susceptibility of each plant. By responding to sap level aberrations, a grower could apply a foliar product to prevent disease occurrence.

Herbicide problems

In many counties a major issue has been symptoms of dicamba particle and vapor drift. With the daily 85+ F temps every day during late May and June the ideal application days were few. Certain applicators avoided all caution in order to beat the spray deadlines. Having dry soils is known to promote vaporization of the herbicide from the soil and leaves. The air was filled with the products from many sources for days and it drifted for many miles. Might we have a day when see a group of harmed growers sue the offending companies for extortion when the innocent parties are forced to buy seed solely to avoid drift damage?.

Be observant in your travels of the larger and older heritage trees that are losing leaves and limbs. Ignore the ash trees as they have their insect and fungal problem. This collateral damage and loss of landscape trees will become too much to ignore. Many large prized trees have already been lost.

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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