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Corn Newsletter : 2019-35
Sampling for Soybean Cyst Nematode – Fall is the time!Author(s): Anne Dorrance
Harvest is well underway and once the soybeans are off the fields this provides some time to sample soil for the SCN populations. The SCN Coalition theme for the next few years is What’s your number? Do you know which fields have SCN and what the current population is sitting at? If its high, then there is a second number – what is the SCN type? Which addresses the bigger question can it reproduce on the SCN resistance source PI 88788 or Peking. All of these numbers can impact management of this root pathogen and future losses.
The situation in Ohio: We know that the state is now “polluted” with SCN, fortunately most of those fields are at very low levels – which is where they should be kept.
From samples received to date of a statewide survey for Ohio of 50 counties as part of the SCN Coalition sampling, here are the numbers from 378 fields.
SCN Population Level Total Fields % Processed None detected 151 39.9 Trace (40-200) 91 24.0 Low (200-2000) 79 20.9 Moderate (2000-5000) 34 8.9 High (5000+) 24 6.3 Total 378
Yield losses have been measured as high as 25% with no above ground symptoms in populations of 2,000 and higher.
Summary to date:
- 60% of the Fields sampled in 2018 and 2019 in Ohio have detectable levels of SCN
- 15% of these have populations at economically damaging levels – do you know your number?
If your SCN report in the past has come back as:
- Not detected: this is not surprising. Remember that SCN sits in pockets and can we quite variable. Continue to monitor your fields.
- Trace: May begin to measure some yield loss on susceptible varieties, especially on lighter soils.
- Low: Plant SCN resistant varieties or rotate to a non-host crop (corn or wheat).
- Moderate: Rotate to a non-host crop and follow with SCN resistant varieties the following year. We have planted susceptible varieties in fields with this level of SCN and have recorded 20 to 50% yield loss.
- High: rotate to a non-host crop for two to three years, then sample SCN to determine if populations have declined to a level where soybeans can be planted again.
SCN is picky about what it feeds and reproduces on but it does like a few weed hosts and cover crops as well as soybean. If you have SCN in your fields , it is important to also control winter annuals such as purple deadnettle, but also avoid cover crops such as several of the clover’s, cowpea and common & hairy vetch.
So it is time to sample! We recommend sampling in the fall – because in most cases this is what the population will be in the spring. With the warmer weather this year and hopefully no frozen ground should give ample time to collect and process the samples in plenty of time for spring planting. Processing of samples does cost time and money, so here are a few thoughts on how to sample or how to target your sampling to get the best information for your money.
For several counties there is still free sampling available please contact your county educator to target some of those problem (low yielding) fields.
Updated information on where to send the samples for processing for a fee:
OSU C. Wayne Ellett Plant and Pest Diagnostic Clinic
8995 E. Main St. Bldg 23
Reynoldsburg, OH 43068
www.ppdc.osu.edu - follow this link to download forms to go along with the samples
Spectrum Analytic Inc.
1087 Jamison Rd. NW
Washington Court House, OH 43160
For some additional information on Management of SCN – always check Ohio’s SCN fact sheet and several other resources as well: https://u.osu.edu/ohscn/
https://soybeanresearchinfo.com/soybean-disease/soybean-cyst-nematode-scn/- link to the 5th edition of the SCN guide developed through the North Central Soybean Research Program.
Link to recent findings and sampling protocol for SCN: https://www.youtube.com/watch?v=FQgg-UPQdcs&feature=youtu.be
Managing Phosphorus for Yield and Reduced Edge of Field LossesAuthor(s): Greg LaBarge, CPAg/CCA
A new factsheet highlights eight steps to reducing edge of field P losses while maintain soils for increase crop production. The Phosphorus Nutrient Management for Yield and Reduced P Loss at Edge of Field-AGF-509 (https://ohioline.osu.edu/factsheet/agf-509) highlight practices that can be used to reduce edge of field losses of P. There are eight field specific steps to considered.
- Control erosion
- Identify surface inlets to tile and use appropriate practices to reduce surface losses
- Consider ground and weather conditions prior to application of fertilizer and manure
- Take a representative soil test
- Use soil test as screening tool to meet crop production and water quality goals
- STP value of 40 PPM Mehlich III or less:
CROP YIELD—Reduce risk of crop yield losses with nutrient application.
- A STP of 20 PPM defines the critical level. At 20 PPM or less, the risk of yield loss increases. Annual in season P nutrient application recommended. Recommendations to build STP to critical level are available.
- The maintenance STP range is 20–40 PPM. Recommended rate of P is equal to P removed in harvested crop. Annual application is not required. Risk of yield loss is low with flexibility to delay application one (or more) growing seasons, if needed.
WATER QUALITY—The greatest risk for event P losses occur when nutrient application is followed by runoff-producing rainfall. Use the following steps to reduce P loss risk at application:
- Use an agronomic rate of no more than two years’ worth crop removal as recommended in the Tri-State Fertilizer Recommendations.
- Time fertilizer applications so predicted rainfall 12 hours after application is less than a 50 percent chance of more than 1 inch of rainfall.
- Time organic nutrient applications so predicted rainfall 24 hours after application is less than a 50 percent chance of more than 0.5 inches of rainfall.
- Subsurface placement reduces losses over surface application.
7. STP value above 40 PPM Mehlich III:
CROP YIELD—Response to fertilizer with STP greater than 40 PPM is highly unlikely.
- Do not apply additional fertilizer due to lack of economic return.
- Organic applications should be determined using P content from testing the organic source and not exceed P crop removal rate for the next two (and no more than three) crops in the rotation.
- Consider in-crop application to a nitrogen-using crop to reduce purchased N, maximizing economic return to organic application.
- Where in-crop application is not used, incorporate organic nutrients.
WATER QUALITY—The risk of P loss increases with STP values over 40 PPM, with greater risk after 150 PPM.
- Do not apply additional fertilizer: due to lack of economic return.
- Do not make organic applications when STP is greater than 150 PPM.
- Follow NRCS 590 site and rate criteria between 40 to 150 PPM. • Time organic applications so predicted rainfall 24 hours after application is less than a 50 percent chance of more than 0.5 inches of rainfall.
- Use the Ohio P risk index, field scale hydrology/water quality models, or monitoring to evaluate site risk for P losses and need for further site BMPs. See step 8.
8. BMPs for high risk P loss sites: Monitor fields for P loss using the Ohio P risk index and field scale hydrologic and water quality models. For sites with predicted high P losses, consider one or more of the following water management practices based on fitness and cost effectiveness for field site:
- Production practices that increase soil organic matter to retain water on site
- Drainage Water Management (NRCS 554)
- Nutrient removal wetlands (NRCS 656)
- P Precipitating Filter
- Saturated Buffer (NRCS 604)
- In-field water storage or detention basins
2019 Ohio Soybean Performance Trial- South Region Results Available
The South Region results of the 2019 Ohio Soybean Performance Trials are available online here: https://stepupsoy.osu.edu/news/2019-ohio-soybean-performance-test-south-region-results Results from the north and central regions will be added as harvest continues.
Early soybean varieties (2.7 to 3.6 RM) yielded an average of 60.4 and 49.0 bu/acre in Preble and Clinton County, respectively. The late soybean varieties (3.7-4.4 RM) yielded an average of 66.4 and 58.7 bu/acre in Preble and Clinton County, respectively.
Surface Application of Manure to Newly Planted Wheat FieldsAuthor(s): Glen Arnold, CCA
Several livestock producers have inquired about applying liquid dairy or swine manure to newly planted wheat fields using a drag hose. The thought process is that the fields are firm (dry), there is very little rain in the nearby forecast, and the moisture in the manure could help with wheat germination and emergence.
The manure nutrients could easily replace the commercial fertilizer normally applied in advance of planting wheat. The application of fall-applied livestock manure to newly planted or growing crop can reduce nutrient losses compared to fall-applied manure without a growing crop.
Both swine and dairy manure can be used to add moisture to newly planted wheat. It’s important that the wheat seeds were properly covered with soil when planted to keep a barrier between the salt and nitrogen in the manure and the germinating wheat seed. It’s also important that livestock producers know their soil phosphorus levels, and the phosphorus in the manure being applied, so we don’t grow soil phosphorus levels beyond what is acceptable.
If the wheat is planted at its typical one-inch depth and swine or dairy manure is surface applied there should be no problem applying 5,000 gallons per acre of swine manure or 8,000 gallons per acre of dairy manure. If the wheat is emerging when manure is being applied, there is the possibility of some burn to the wheat from swine manure, but this has not happened in fields I have looked at in past years. If the wheat is fully emerged, there is little concern for burning.
If incorporating manure ahead of planting wheat, try to place the manure deep enough (at least three inches) so the manure does not impact the germination and emergence of the wheat crop. Another option is to incorporate the manure and wait a few days before planting the wheat. If incorporated, the opportunity to carry some of the manure nitrogen through the winter could allow for a reduction in the amount of topdress nitrogen needed for the wheat crop next spring.
The application of 5,000 gallons of swine finishing manure could contain 200# of nitrogen, 100 pounds of P2O5 and 150 pounds of K2O. The application of 8,000 gallons of dairy manure could contain 175 pounds of nitrogen, 60 pounds of P2O5 and 150 pounds of K2O. Manure nutrient content can vary tremendously from one manure storage facilitate to another but stay reasonably consistence from the same facility year after year.
As always, print out the weather forecast when surface applying manure. Remember the “not greater than 50% chance of 0.5 inches of rainfall in the next 24 hours” rule in the western Lake Erie watershed. Also be certain to observe the proper setbacks from ditches and streams.
Tar Spot of Corn in Ohio Again this 2019
Tar Spot, a new disease of corn caused by the fungus Phyllachora maydis, was reported for the first time in Ohio at the end of the 2018 growing season. At that time, it was found mostly in counties close to the Indiana border, as the disease continued to spread from the middle of country where it was first confirmed in 2015. Over the last few weeks, there have been several new, confirmed report of Tar Spot in Ohio, this time not only in the northwestern corner of the state, but also from a few fields in central and south-central Ohio. As was the case last year, disease onset was late again this year, with the first reports coming in well after R4. However, some of the regions affected last year had more fields affected this year, with much higher levels of disease severity. It could be that Tar Spot is becoming established in some areas of the state due to the fungus overwintering in crop residue from one growing season to another. This is very consistent with the pattern observed in parts of Indiana and Illinois where the disease was first reported. We will continue to keep our eyes out for Tar Spot, as we learn more about it and develop management strategies. You can help by looking for Tar Spot as you walk fields this fall, and please send us samples.
What does it look like? Even though corn is drying down, if Tar Spot is present, you can still detect it on dry, senescent leaves almost as easily as you can on healthy leaves. So, please check your fields to see if this disease is present. “Symptoms of tar spot first appear as oval to irregular bleached to brown lesions on leaves in which raised, black spore-producing structures call stroma are formed... giving the symptomatic areas of the leaf a rough or bumpy feel to the touch… resembling pustules on leaves with rust. Lesions … may coalesce to cause large areas of blighted leaf tissue. Symptoms may also be present on leaf sheaths and husks.” As the name of the disease suggests, symptoms look like the splatter of “tar” on the leaves. In some cases, each black tar-like spot may be surrounded by a necrotic halo, forming what is referred to as “fish-eye” lesions.
What causes Tar Spot and how damaging is it? In the past, the greatest impact of this disease in terms of yield loss were observed when P. maydis-infected plants were co-infected with a second fungus called Monographella maydis. In other words, the damage tended to be much more severe when the two fungi worked together to affect the plant. So far, only the first fungus, P. maydis, has been reported in the US, but based on work done in Illinois, this pathology alone is capable of causing substantial yield reduction on highly susceptible hybrids when conditions are favorable and infections occur early.
Where did it come from and will it survive and become established? At this point it is still unclear as to how Tar Spot got to the US in the first place and how it continues to spread. The fungus is not known to be seed-borne or infect other plant species, so corn seeds and weeds are unlikely to be the sources of inoculum. However, the fungus can survive and be moved around on fresh and dry plant materials such as leaves and husks. In addition, since spores of the fungus can be carried be wind, it could be blowing in from neighboring states/counties/fields. Although not yet confirmed through survival studies, it appears that the fungus could be overwintering in infected crop stubble between growing seasons.
What should I do if I find Tar Spot? If you see anything that fits the description of, or resembles (Picture) Tar Spot, please inform your state specialist, field specialist, or county extension educator, but most importantly, please send samples to my lab (1680 Madison Ave, Wooster, OH) for confirmation. We will also be using your samples to study the fungus in order to develop effective management strategies.
Read more about Tar Spot of Corn at:
New and Upcoming Episodes of the Agronomy and Farm Management Podcast Focus on Harvest and Compaction
The Agronomy and Farm Management Podcast has new episodes available to check out. Episode 36 features an interview with Jason Hartschuh and Will Hamman where we discuss tips for harvesting late planted or drought stressed crops this fall. This episode is a must listen to help maximize the amount of your crop that will make it to the elevator or bin even with the variability we are seeing in crop yields and quality.
Episode 37 will be released Wednesday, October 16 and focuses on compaction. The extremely wet fall in 2018 and spring in 2019 led to field operations needing to be conducted even when soil conditions were not ideal increasing the risk of soil compaction occurring. Dr. Scott Shearer sits down with us to talk about soil compaction, what it is, the causes, how to avoid it, and how to mitigate it. To listen or learn about the podcast, visit go.osu.edu/AFM.
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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