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Corn Newsletter : 2016-07
How Low Can You Go? Cold Weather and Wheat Injury
Cool weekend temperatures have prompted some concern about possible injury to the wheat crop.
The effect of cold weather depends on the wheat growth stage. Maximum resistance to cold weather occurs in December-February. As wheat greens-up, the plant becomes less tolerant of freezing temperatures. At Feekes 6 growth stage aka “jointing” temperatures of ≤24°F for at least two hours may be injurious. Currently, in Ohio, most wheat is at Feekes 5 (green-up), so injury should be minimal.
Currently, we are in the process of evaluating freeze tolerance of winter wheat grown in Ohio. We collected wheat samples from Pickaway County on March 30 when plants were at Feekes 5 growth stage. Plants were put into a freeze chamber and temperature lowered to 27°, 21°, 14°, and 5°F. Very little injury has been observed between 14-27°F. At 5°F, wheat leaves wilted and had a dark purple-green water-soaked look 24 hours later (see picture). We plan on re-running this study at Feekes 6 growth stage.
Reference. Shroyer, J.P., M.E. Mikesell, and G.M. Paulsen. 1995. Spring Freeze Injury to Kansas Wheat. Agricultural Experiment Station and Cooperative Extension Service. Available at: http://www.ksre.k-state.edu/bookstore/pubs/C646.PDF
Mild winter, Pathogen Survival, and Early Disease Development
When the winter is as mild as it was this past year, pathogens that would have otherwise been killed or at least suppressed by the cold temperatures end up surviving and getting an early start to infect our crops. With the exception of the rust fungi, most of the pathogens that cause leaf spots and blights and ear rots and molds have developed strategies to survive our usually harsh winters. But even so, cold, dry winter conditions do contribute to reducing pathogen survival is a “normal” year. However, when temperatures during the winter months are not consistently low, even pathogens like the rust fungi that do not usually survive well here in the Midwest are able to overwinter on volunteer plants and in cultivated fields.
This was certainly the case in wheat this year. Very late in the fall and during the first few weeks of the winter, pustules of leaf rust and powdery mildew were seen in several fields across the state. This is not uncommon, but the fact that these diseases are already being reported at fairly high levels now that the winter is “over” suggests that those fall infections carried over into the spring. Although Septoria and Stagonospora leaf blotches have not yet been reported, it is highly likely that the fungi causing these diseases also survived the winter in higher-than-usual numbers and will likely infect the crop as conditions begin to warm up, especially is it stays wet over the next few weeks. For powdery mildew, a disease that thrives in dense wheat stands with high nitrogen, severity will likely increase after the wheat is top-dressed.
Rust, powdery mildew, Septoria and Stagonospora are all polycyclic diseases, meaning that once they get an early start, several batched of spores will be produced between now and grain-fill, if not managed and conditions are favorable. Spores produced early in the season will spread up the plant and to neighboring plants, causing new lesions or pustules to develop, and these new lesions will themselves produce new spores within 7-14 days that will again infect new leaves and plants, causing the diseased to spread rapidly, particularly if the variety is susceptible. The more cycles we have, the more disease we will see and the greater the grain yield and quality reduction. Keep monitoring the progress of these diseases and be prepared to apply a fungicide. We typically do not recommend fungicide application at green-up for foliar disease control, since we rarely see high levels of disease this early, however, this may be the year for a green-up application if it stays cool and your variety is susceptible. Remember to always use label-recommend rates; half-rates do not provide adequate protection and may increase the risk of fungicide resistance. Also, early applications will not protect the flag leaves and spikes against infections later in the season.
Here is a word for our corn producers as well. As you get ready to plant corn, make sure you select hybrids with resistance to northern corn leaf blight (NCLB) and gray leaf spot (GLS). Just like the wheat pathogens, the NCLB and GLS fungi likely survived the mild winter and will be producing lots of spore by the time the crop is planted. If the hybrid is susceptible and the weather is as wet and humid as it was last year, we will again see NCLB and GLS (as well as other diseases such as eyespot caused by residue-borne pathogens) developing well before pollination. Again, if the hybrid is susceptible and the weather is favorable, early disease = more disease = greater yield reduction, if not managed. NCLB and GLS are also polycyclic. Start by selecting resistant hybrids! Click on the link below for more on NCLB resistance: https://agcrops.osu.edu/newsletter/corn-newsletter/select-hybrids-resist...
Modified Relay Intercropping in Wide Row WheatAuthor(s): Jason Hartschuh, CCA
Modified relay intercropping of soybeans into wheat is a very versatile system across many row spacings. Over the past 17 years of intercropping at OSU Unger Farm, three rows spacings have been used. Ten inch spacing was used for the first 15 years, but this period also included three years of 15 inch work. The last two years, twin row wheat has been grown. The variations in row spacing show the flexibility of wheat to respond to various stresses. According to the Ohio Agronomy Guide, as wheat rows increase from 7 inches to 15 inches, yield declines on average by 4 bushels per acre. The complexity of the intercropping system though decreases with wide row wheat.
Some of the basic concepts apply across all three spacings, such as needing to plan for tramlines, where the tractor and planter will run, before it is time to plant the soybeans. In 10 inch row spacing, wheel traffic tramlines for at least the tractor need to be planned for at planting. This will usually mean blocking off rows of wheat so that they do not plant, creating a 20 inch tramline gap for the tractor to follow. In wider wheat rows over 15 inches, it is possible to select tractor tires and align planter tires to fit in the row gaps without eliminating any wheat rows. Without having to plan for tramlines, it simplifies the system a lot. Another benefit to the soybeans of moving to wide row wheat is earlier planting dates of the soybeans. In 10 inch soybeans, our typical planting recommendation was from head emergence through pollen shed. Some producers would plant over a week after pollination was complete. This would lead to a soybean yield below 5 bushels per acre in one out of five years, despite our average of 33 bushels per acre. We didn’t want to plant soybeans any earlier in this system due to low sunlight below the crop canopy causing the soybeans to have very long internodes which could lead to lodging as they stretched to find light. Since going to twin row spacing, we have been looking at earlier soybean planting dates to hopefully increase soybean yields. Our two current wheat growth stages for planting soybeans have been Feeks 10 and Feeks 10.5 (the earliest of planting dates for 10 inch wheat). Over the last two years, our soybeans’ yield has averaged within a bushel for these two planting dates. Averaging 3 maturities together, this average is 41.6 bushels. When comparing maturity groups, we see a range in yield from 36.5 bushels to 46 bushels for a 2.9 and a 3.8 soybean respectively. From these results, there appears to be an advantage to selecting the best yielding, longest maturity soybean for your area to intercrop. Also, work done by Jim Beuerlein in the late 80’s showed that the best intercrop soybean yields occurred with an early May planting date when wheat was between 10 and 20 inches tall and the wheat and soybean row spacing was 14 or 21 inches. This work also showed that the ideal maturity in Wooster was a full season soybean, between a 3.9 and 4.5 maturity, which mirrors our current work.
This past year I have been receiving more calls about pushing the planting date even further ahead than Feeks 10, possibly to Feeks 5. While there seem to be many planting advantages to this idea, since the wheat has not gone through stem elongation and can still be drove over without causing damage, it is not without its own set of challenges. While we plan to look into earlier planting dates this year, a strip plot we planted last year at Feeks 6 showed some of the challenges producers planting this early may face. The challenges we saw matched what producers planting at these early dates have told us. The challenges come mostly at harvest. The soybeans will most likely be as tall as the wheat at this time, which requires special cutter bar covers on your grain table or using a row crop head to harvest the wheat without causing excessive clipping damage to the soybeans. If you are interested in the various MRI trials that have been conducted at OSU Unger Farm, visit the OSU Extension Agronomic Crops Team on-farm research site and search for “Modified Relay Intercropping” https://agcrops.osu.edu/on-farm-research.
Timing of Vertical Tillage and Herbicide ApplicationsAuthor(s): Mark Loux
One of the questions that has come up repeatedly over the past year or so concerns the appropriate order of vertical tillage versus herbicide application in the spring. Two general principles guide our thinking on this issue: 1) if possible, foliar burndown herbicides should be applied to undisturbed weeds that are not partially or fully covered with soil; and 2) residual herbicides should left on the surface undisturbed by tillage (allowing rain to move herbicide into the soil) following application unless that tillage will uniformly mix herbicide with the upper couple inches of soil.
It can be possible to accomplish the second of these in a no-till field with the appropriate combination of soil tilth, well-distributed crop residue, and an effective tillage tool. This does not describe the situation where vertical tillage occurs, since it fails to uniformly mix soil where the blades/discs run and leaves other areas of the soil surface undisturbed. This is of course why there still needs to be a comprehensive burndown herbicide treatment – the vertical tillage does not effectively remove all of the weeds. One option that avoids the problems with burndown activity versus residual distribution is to make two herbicide applications.
Burndown herbicides can be applied prior to the tillage, followed by residual herbicide application after the tillage. Sounds like extra work and expense for sure. Aside from this, our best assessment where everything needs to happen within a short period of time prior to planting, is that the vertical tillage should occur first, followed by the burndown/residual herbicide application. There may be a benefit to delaying the herbicide application for a while if possible, to allow weeds disturbed by the tillage to recover somewhat.
Where the order of operations is reversed, the best-case situation would probably be to apply residual herbicides far enough in advance of tillage that substantial rain occurs. The rain can move herbicide into the soil profile, which may reduce the negative effect of vertical tillage on herbicide distribution, compared to when all of the herbicide is still sitting on the soil surface. This is an area that we do not have a lot of experience with, so if you have developed a foolproof approach be sure to let us know.
What is the Meaning of Feekes Growth Stages in Wheat?
There are at least five growth scale systems developed worldwide for wheat, the one we often use is the Feekes scale. This scale uses a numbering system 1 through 11 with each number representative of a new growth event. Each number may be further divided by using decimals to further describe a given stage. A wheat field reaches a new growth stage when more than 50% of the plants are at the next stage.
The early stages may be collectively referred to as the vegetative stages since the growing point is below the soil surface and protected from above ground environmental and pest issues. These stages would include Feekes 1 – 5. After vernalization and growth stage 5, the tissue in the growing point has differentiated to include reproductive tissue in reproductive tillers and will be pushed above the soil surface at growth stage 6. Collectively, Feekes 6 – 11 may be referred to as the reproductive stages. Currently wheat fields in Ohio are at Feekes Growth Stage 5. A description of each Feekes Growth Stage is given below:
Feekes 1.0: germination period to the first emerged leaf. The number of leaves present on the first shoot can be designated with a decimal. For example, 1.3 is a single shoot with three leaves unfolded. This stage would have occurred last October.
Feekes 2.0: tillers become visible. A tiller is a new shoot that originates underground off the main stem.
Feekes 3.0 – 4.0: tiller formation. Wheat generally will generate three to five tillers in the fall prior to the onset of winter depending on planting date. These tillers will contribute the most to grain yield. Additional tillers may develop in early spring.
Feekes 5.0: strongly erect leaf sheaths. Plants will have an upright appearance but the growing point is still below the soil surface.
Feekes 6.0: first node visible. On reproductive tillers a visible knot, bump, or swollen tissue called the node is noticeable above the soil surface. The growing point, which includes the developing head or spike on reproductive tillers is above this node. Tiller production has ceased and wheat head development will continue on reproductive tillers. See the previous newsletter for a more detailed description of this stage, https://agcrops.osu.edu/newsletter/corn-newsletter/winter-wheat-progress....
Feekes 7.0: second node becomes visible. This stage is characterized by the rapid stem elongation and further development of the head or spike.
Feekes 8.0: flag leaf visible. This growth stage begins when the last leaf (flag leaf) begins to emerge from the whorl, and the second node is visible. The flag leaf will contribute 75% of the energy needs of the developing grain.
Feekes 9.0: Flag leaf completely emerged. Complete emergence is defined when the leaf ligule is visible. The ligule is a membranous structure found at the collar or the location where the leaf blade and leaf sheath join at the stem. The flag leaf will the last leaf on the reproductive tiller. Feekes 10.0: Boot stage. The head or spike is fully developed and can be seen in the swollen section of the leaf sheath below the flag leaf.
Feekes 10.5: Heading and flowering. When the head is fully emerged the stage is further designated as Feekes growth stage 10.5. Heads generally emerge mid to late May depending on the location in the state. Flowering will generally follow within five to seven days after emergence depending on temperature. Flowering is further divided using decimals: Feekes 10.5.1 (early flowering –anthers are extruded in the center of the head), 10.5.2 (mid flowering –anthers are extruded in the center as well as top of the head), and 10.5.3 (late flowering – anthers are extruded in the center, top, and base of the head).
Feekes 11.0: Ripening. The last stage and further divided by the characteristics of the maturing grain. These subdivisions include: milk stage (11.1), mealy stage (11.2), hard kernel (11.3) and harvest ready (11.4). Temperature and daylength will determine how quickly a wheat crop moves through each stage.
A video may be found showing various growth stages at the following sites:
Feekes 7 & 8: https://www.youtube.com/watch?v=PZ7Lvsux1y8
Feekes 9 & 10: https://www.youtube.com/watch?v=OHGhq0qSM1o
Wheat heading: https://www.youtube.com/watch?v=Q6Da1HRlmV8
The Big Data Confusion: Part 4 – Collection, Access, and Control
This week’s installment of “The Big Data Confusion” highlights “Collection, Access and Control”. According to the Privacy and Security Principles for Farm Data, “an ATP’s collection, access and use of farm data should be granted only with the affirmative and explicit consent of the farmer. This process will be by contract agreements, whether signed or digital.” This particular principle is a great follow-up from last week’s ownership discussion. Ownership designates control but also the responsibility to properly control and managed your data. Contract agreements related to data collection and services must be reviewed today with considerations around who you are providing consent and access to when hitting the “I accept” button or signing on the line. Reviewing contracts, data policies and terms & conditions is a must if data ownership and control are important. You need to understand who can have access to your data.
This principle leans heavily on education. Producers need to be educated on the contents of their contract agreements, a company’s data policy, and stated terms & conditions. When you as a farmer sign contracts (pen and ink or digital), clearly understand what they are consenting to within the contract. The important point is understand who, or what entity, has the right to collect, access and control farm data with these 3 components clearly spelled out in any contract agreement or terms & conditions.
About the C.O.R.N. Newsletter
C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.
The information presented here, along with any trade names used, is supplied with the understanding that no discrimination is intended and no endorsement is made by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.
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