Excerpts from crop consultant Bob Streit's newest field report

Here are some paragraphs from veteran crop consultant Bob Streit's report to clients. Of particular relevance to WakeUP is Bob's observation that trace element deficiencies which show up in tissue tests can be countered with late-season foliar feeding, based on tissue tests. Sap tests are also a good guide. Our recommendation if you make foliar applications: Spray in the cool of morning; pull out of the field as temps rise toward 80 degrees. Use WakeUP for good leaf coverage and rapid nutrient translocation. 

July 25, 2021  By Bob Streit

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 of fungicides 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, there are 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 plant needs is thru foliar applications or possibly thru 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 nodulation.

Bob Streit

The Corn Crop

People are asking us if the top end of the corn crop has been hurt. There is a website that actually tallies the stress degree days accumulated each season. Nearly every day in June 2021 accumulated stress hours. Early in the season, corn can tolerate tough conditions. 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 this week, and 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 kernels will reach the blister stage and prone to aborting a few too many rings of kernels.

Strong winds accompanied the rains in many areas. Many fields of second year corn that had corn rootworm (CRW) damage had not grown recovery roots. These fields showed varying degrees of root lodging. In a dry year, losing a major percent of corn roots can affect yield significantly. At that stage of development, corn plants 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 new methods of controlling CRW. One that 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 2000s a CRW control program originated from a team of Beltsville, MD entomologists. They discovered a genetic throwback watermelon that tasted extremely bitter. 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 spray alternative field 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 we're working to make that happen.

Also, Chrome has proven effective in heavy CRW 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. Eyespot tends to multiply on days with dews that keep the leaves wet thru mid-morning.

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 the late Dr. Bruce Tainio, a very wise plant scientist from Spokane, WA who passed away in 2009. Bruce and John advised 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 we see a group of harmed growers sue the offending companies for extortion when the innocent growers are forced to buy dicamba-tolerant 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.