For one to two months now we have peered into the western sky or onto a radar map to see when our next major rains would arrive. For a high % of the people involved in farming, other profession or activity directly dependent on mother nature to deliver our needed rainfall we have been left wondering why the large front or storm cluster detoured to the north or south, or only left a few lightning strikes instead of a meaningful amount of moisture in the gauges. Close does not count when our crops are thirsty. It has to be measurable and end up in the rain gauge. We have had a bit of a reprieve with the temps cooling down into the 70s for a few days. That lowers the evapotranspiration rate lettings the crops hang on for a few more days. The words of wisdom provided years ago by an old Oklahoma farmer is that ‘it always rains at the end of a dry spell’.
So are our crops and their expected yields going to be affected? Anyone who has walked into the fields and looked at the still flat pods or pulled the husks down on a few ears knows the answer to that question. Why haven’t the markets or traders in Chicago reacted in a positive fashion? Part of that may be that so many crop conditions are based on computer projections and modeling. A high percentage of the states still have their two major crops rated in the 75 + % good to excellent categories. In reality those who network across the major crop growing midsection of the country know that the area deemed extraordinarily dry thru moderate or extreme drought runs from Pennsylvania to the SW part of Colorado. There are parts of the southern Midwest as in Missouri and Arkansas and in the northern tier of states such as the Dakotas, Minnesota and Wisconsin that have been supplied regularly with good rains all season.
Eventually the rains will resume falling. Will the corn and bean plants still be alive and where the kernels and seeds will be able to increase their size? Will the rains come in amounts to hinder the harvest, what there will be of it? It’s too bad that Mother Nature could not save some of the excess rains from 2018 and 2019 and deliver them now when they would be appreciated.
Corn and Bean Crop Observations
For a few weeks being inside hot and sweaty corn fields was uncomfortable. Because plants are not mobile climatologists wanted a means to measure the cumulative stress the plants had to endure. Dr. Louie Thompson of ISU developed his Stress Degree Measuring System where they recorded the daily temperatures exceeding 86 F. He and Dr Taylor recognized there needs to be a moisture deficit component to it, since corn tolerates temps up to 92 F if they have enough moisture, but uneven rainfall made the site specific calculations more difficult. Once the cumulative totals exceeded 140 the temps could become a negative and start subtracting from yield. I mentioned in my previous column that several sites in Iowa had already exceeded the 140 by July 20th, with the regional tallies varying across the state. The damage resulting from excessive heat can now be seen as bubble kernels, open kernels sites, aborted tip kernels and plants that are wilting severely from a moisture shortage in the root zone. Many ears across from the entire Midwest have lost 2” to 3” of tip kernels with most shallower than normal. My field observations this week in Story and Boone counties detected many ears that are 60 to 80% dented already. That figure can result as being positive or a negative in that those plants having the majority of their grain filling completed before the moisture runs out completed that task. It also means that when we start receiving adequate rain the fully dented of black layered plants can’t reverse course and return to the task of starch accumulation. North of Hwy 3 the plants are not as advanced in maturity and could still capitalize on late rains.
As is typical most articles and field interviews about the crop focused on the pollination and fertilization events as though they were the sole criteria of bounteous yields. I am more concerned about the degree of stress endured by the plants in the 10 to 14 days following fertilization that can lead to kernels abortion. Knowing that our stress day accumulation was high during those days and seeing the resulting shallow kernels and multiple inches of tip back, it suggests the NASS good to excellent ratings of both crops have to be questioned. Once a person gets beyond the end rows in most corn fields conditions change. For any crop modeling company to pronounce a statewide IA corn yield average of 201, NE at 183 and KS at 131, they can be accused of counting their chickens way too early. Losing 1/3 to ¼ of the tip kernels coupled with kernels only half of normal depth projects to how many bushels?
In areas not receiving rain in the past month the beans range from having a very good yield potential with lots of unfilled pods and with three or more side branches to only 12 to 13 podded nodes with few branches. Early planting led to forming more podded nodes. The extra side branches can form if cytokine hormone levels are high in the plants, mineral and amino acid levels are high, or if plant selection by the SB breeders used branching ability as a selection criteria. Another plant trait seen in certain genetic lines in the past 3 or 4 years has been the formation of flower racemes at the nodes. This is typically a characteristic seen in determinant varieties in South America.
As of Aug 6th very little pod fill has occurred. It is critical that rain begins falling, or we will see the formation of ethylene, the stress hormone, will reach a high enough level to cause abscission layers to form and the pods fall off.
A Mystery or a Deception?
After hearing how the CCP withheld information from the rest of the world on this virus, having Chinese seeds show up in mailboxes in many states, we have to be a bit suspicious of such boxes. It likely was not a Publisher’s Clearance House gimmick. They had to be scanned at the site of origin by one of the PO electronic sorters. Are we being played on this?
Disease Situations in the Midwest
The incidence and severity of foliar diseases on the corn and bean plants typically depend on: the hours of plant wetness or dews, mineral levels within the plant with regard to deficiencies of Mn, Cu, Bo and Zn; the presence of inoculum either floating in from infected fields upwind or from intact residue from an earlier infected crop and; genetic susceptibility of the hybrid to the disease; maturity stage of the crop. Drier parts of the Midwest until recently had very few leaf disease appearing in their corn or bean fields. Now after pollination the immune response in corn is lowered as energy is devoted more to grain fill. The conditions also change in soybean fields as with canopy closure come higher humidity levels and more hours of leaf wetness. Thus with rainfall being more plentiful in Eastern Iowa there has been greater disease pressure.
There are now several diseases now appearing in corn, again more so where tissue tests indicated mineral shortages. The list includes light GLS, a bit of NCLB, Physoderma on the leaves and stalks, Eyespot, Common and Southern Rust, and what may be very small Anthracnose spots which may coalesce as time advances. One also has to acknowledge that as the soils have gotten progressively drier two things happen, the minerals in the soil are less available to the plants due to both soil hydraulics and less biological activity plus less water is available to be pulled into the plant via osmotic pull. This is when if you want to get minerals into the plant the best method would be with Y-drops or foliar application.
In bean fields where the canopies have closed the incidence of dews will increase and we will see more Septoria, Downey Mildew, the two forms of Cercospora, and possibly a few others. The challenge of optimum response to fungicide dollars depends on application timing, penetration of the spray, and residual length of the product(s). It would be helpful to know exactly how long each product can last, but getting exact information is difficult and costly as analytical costs are high. Until now there have not been many systemic product available for use in row crops. The more recently introduce products have such movement in the plant.
Dicamba Damage
It is still readily apparent as to which bean fields, specialty crops or trees suffered from Dicamba drift. The recovery of each bean fields depended on dosage and number of times it got dosed. Recovery percentage varied from good recovery and decent growth to still seeing a large reduction in growth.
Part of the information weighed by the judges on the Dicamba ruling was input from DNR staff who had noted considerable damage done to older trees including oaks and maples. Speaking from observations the burr oaks are highly susceptible with the stunted leaves resembling the distorted growth that a Ni deficiency in pecan tree causes (squirrel’s ear). Hackberry as well as other tree species are also casualties. We have found that applications of several minerals can stimulate new growth. Those we have tried include copper, manganese, and zinc. Having the minerals chelated by amino acids is key due to their systemic movement. The new products from PhytoBiotics have worked very well and we are continuing the testing. The burr oaks sprayed on July 1 formed about 15” of new growth by Aug 3.
I have never had a variegated maple tree, but this year we have several with the leaves looking exactly like bad IDC (iron chlorosis). We are hoping they recover with the mineral application. Pine trees have to be included in the discussion as many windbreaks include those trees on a serious decline. So it appears that rural and town dwellers now have an affordable remedy to treat the trees on their properties.
Insect Threats
So far the most damaging insect seen in 2020 have been the Japanese beetles. They seem to devour exactly the crops you don’t want them to, cherries, berries, corn silks etc. The best remedy for 2021 will be to spray the fungal spore product known as Bb2.5, or Beauveria bassiana, on grassy areas which will then be populated with the fungus that will consume the root feeding larvae. So far the soybean and corn aphid counts remain low. In bad, treatable years the populations had reached treatable populations by July 25th. Spider mites are being found at low levels in both corn and bean fields. These populations can explode as the normal beneficial fungus levels drop and the mite reproductive rate increases with hot and dry weather.
Damage done by treatable sucking insect populations reached the highest % in dry years when the plant sap amounts used to fill the seed were the most limited. A few areas in western IA have been found to have detectable populations of SB gall midge. Without better detection devices or procedures, which may come from research being done by Justin McMehan, from UNL, with collaboration by Erin Hodgsin at Iowa State, we are somewhat in the dark on understanding their biology and potential treatments of them. We have heard of good results where a mix of Bb and Chitosan products was applied to insects using in-season foliar applications on specialty crops in MN and Wisconsin.
On another fruit growing note. My ready-to-pick peach trees were attracting lots of Japanese Beetles. I sprayed them with O2YS, a safe chitosan product that has an organic version and they left and have stayed away. This product causes the trees to produce an enzyme that will dissolve insect parts.
If you get this message in time be aware that the Beck’s Seed field day at Colfax is being held on Aug 11th. They typically do a very good job of presenting valuable info at their tents and on their tour.
Bob Streit is an independent crop consultant and columnist for Farm News. He can be reached at (515) 709-0143 or www.CentralIowaAg.com.