Foliar Diseases May Affect Stalk Strength and Quality

By Pierce Paul, OSU Extension

Causes of Stalk Rot: Several factors may contribute to stalk rot, including extreme weather conditions, inadequate fertilization, problems with nutrient uptake, insects, and diseases. This year, the combined effects of prevalent diseases such as northern corn leaf blight, southern rust, tar spot, and gray leaf spot may negatively affect stalk quality. However, the extent of the problem will depend on when these diseases develop and how badly the upper leaves of the plant are damaged. When leaves above the ear are severely damaged well before grain-fill is complete, the plants often translocate sugars from the stalk to fill grain, causing them to become weak and predisposed to fungal infection. A number of fungal pathogens cause stalk rot, but the three most important in Ohio are Gibberella, Collectotrichum (anthracnose), and Fusarium.

Checking for Stalk Rot: Symptom common to all stalk rots are deterioration and discoloration of the inner stalk tissues. Consequently, you can use the “squeeze test” or the “pinch test” to assess stalk rot and the potential for lodging without having to remove plants and split the stalks. Bend down and squeeze or pinch the internode of the stalk about 6-8 inches above the ground between the thumb and forefinger. If the inner node is easily compressed or collapses under pressure, you will likely have some type of stalk rot. The “push” test is another way to assess stalk rot and the risk for lodging. Gently push the stalks at the ear level, 6 to 8 inches from the vertical. If the stalk breaks between the ear and the lowest node, stalk rot is usually present. Stalk rot severity may vary from field to field and from one hybrid to another.

Consequences of Stalk Rot: Stalk rots may cause lodging, especially if the affected crop is not harvested promptly. On lodged plants, the ear on or close to the ground may develop ear rots and become contaminated with mycotoxins. In addition, lodging may lead to grain yield losses and slowdown the harvest operation.  However, it is not uncommon to walk corn fields where nearly every plant is upright yet nearly every plant is also showing stalk rot symptoms. Many hybrids have excellent rind strength, which contributes to plant standability even when the internal plant tissue is rotted or beginning to rot. However, strong rinds will not prevent lodging, especially if harvest is delayed and the crop is subjected to strong winds and heavy rains. To minimize these problems, harvest promptly after physiological maturity, even if you have to do so at a slightly higher moisture content (moisture in the lower 20s).

Grain Fill Stages In Corn

Please note: While many of the Corn Growth Stages are passed for Paulding County in the article from Bob Neilson, I received a few calls on later stage Corn Growth stages. The article below had some great comparison pictures. 

DATE: AUGUST 18, 2021 – INCLUDED IN ISSUE:

A stress-free grain fill period can maximize the yield potential of a crop, while severe stress during grain fill can cause kernel abortion or lightweight grain and encourage the development of stalk rot. The health of the upper leaf canopy is particularly important for achieving maximum grain filling capacity. Some research indicates that the upper leaf canopy, from the ear leaf to the uppermost leaf, is responsible for no less than 60% of the photosynthate necessary for filling the grain.

Kernel development proceeds through several distinct stages that were originally described by Hanway (1971) and most recently by Abendroth et al. (2011). As with leaf staging protocols, the kernel growth stage for an entire field is defined when at least 50% of the plants in a field have reached that stage.

Delayed planting of corn decreases the apparent thermal time (GDDs) required between planting and physiological maturity (Nielsen, 2019). A large proportion of that decrease occurs during grain filling and may be partially related to shorter and cooler days in late September and October that naturally slow photosynthesis and encourage plant senescence.

Silking Stage (Growth Stage R1)

Silk emergence is technically the first recognized stage of the reproductive period. Every ovule (potential kernel) on the ear develops its own silk (the functional stigma of the female flower). Silks begin to elongate soon after the V12 leaf stage (12 leaves with visible leaf collars), beginning with the ovules near the base of the cob and then sequentially up the cob, with the tip ovules silking last. Consequently, the silks from the base half of the ear are typically the first to emerge from the husk leaves. Turgor pressure “fuels” the elongation of the silks and so severe drought stress often delays silk elongation and emergence from the husk leaves. Silks elongate about 1.5 inches per day during the first few days after they emerge from the husk leaves. Silks continue to elongate until pollen grains are captured and germinate or until they simply deteriorate with age.

Silks remain receptive to pollen grain germination for up to 10 days after silk emergence (Nielsen, 2020b), but deteriorate quickly after about the first 5 days of emergence. Natural senescence of silk tissue over time results in collapsed tissue that restricts continued growth of the pollen tube. Silk emergence usually occurs in close synchrony with pollen shed (Nielsen, 2020c), so that duration of silk receptivity is normally not a concern. Failure of silks to emerge in the first place (for example, in response to silkballing or severe drought stress) does not bode well for successful pollination.

Pollen grains “captured” by silks quickly germinate and develop pollen tubes that penetrate the silk tissue and elongate to the ovule within about 24 hours. The pollen tubes contain the male gametes that eventually fertilize the ovules. Within about 24 hours or so after successfully fertilizing an ovule, the attached silk deteriorates at the base, collapses, and drops away. This fact can be used to determine fertilization success before visible kernel development occurs (Nielsen, 2016).

 

Silk appearance at R1

Closeup of ovules and R1

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Will a Second Fungicide be Worth the Cost for Tar Spot Management?

Please note: While I have not observed Tar spot in Paulding County, we have had many reports of Tar spot in Hardin and Hancock Counties, and in previous years in Fulton County. Please contact Sarah Noggle if you believe you have Tar spot.  

CPN 2018. Published August 19, 2021. DOI: doi.org/10.31274/cpn-20210820-1

By:  Darcy Telenko, Purdue University; Martin Chilvers, Michigan State University; Alison Robertson, Iowa State University; Albert Tenuta, Ontario Ministry of Agriculture, Food, and Rural Affairs; and Damon Smith, University of Wisconsin-Madison.

Tar spot has quickly become a widespread concern on corn this season (2021) across much of the upper Midwest U.S. and portions of Ontario, Canada. This is especially concerning after reasonably localized epidemics resulted in low or no yield reductions over the past two seasons. This season the tar spot fungus has infected corn plants early and is rapidly increasing in many areas of the upper Midwest corn belt. The speed at which the epidemic is now moving and the crop growth stage across much of these acres (ranging from tassel to early dough) has resulted in questions about what in-season management approaches might provide an economic benefit.

Characteristic tar spot signs on a corn leaf. Image: Darcy Telenko

When is the best time to apply a fungicide for tar spot management?

Like most of the other diseases of corn, the timing of fungicide application to hedge your bets against tar spot generally is at tasseling (VT) to the silking (R1) growth stage. Recent regional research has demonstrated that while there might be little yield benefit with an application at the V6 growth stage, a single application of fungicide at VT-R1 on average can result in as much as 7 bushels or more yield compared to not treating. This is compared to just 2-3 bushels at the V6 timing and suggests that farmers are more likely to recover their fungicide costs if applying just one application at VT-R1. In the absence of tar spot and southern rust, spraying at V6 AND VT-R1 also has not resulted in economically positive returns. This practice, on average only results in an additional 1 bushel of yield compared to one application at VT-R1. There is no considerable return on investment (ROI) with two-pass fungicide programs for many corn diseases. But what about the tar spot situation this season? What do the data say about a second fungicide application to manage tar spot if I have already sprayed at VT-R1 and the disease is continuing to increase?

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Purdue Corn and Soybean Monthly Outlook Webinar on Friday, May 14 – 12:30 – 1:30 PM

Register Now

Upcoming Webinar

MAY CORN & SOYBEAN OUTLOOK UPDATE WEBINAR

Time: 12:30 p.m. – 1:30 p.m. EDT

Date: Friday, May 14, 2021

Join us for our free monthly corn and soybean outlook webinar series

Purdue ag economists Michael Langemeier, Nathanael Thompson, and James Mintert will host a free Corn and Soybean Outlook monthly webinar series for the remainder of 2021. Each webinar will follow the release of that month’s U.S. Department of Agriculture’s Crop Production and World Agricultural Supply and Demand Estimates (WASDE) reports. Continue reading

Livestock and Grain Producers: Dealing with Vomitoxin and Zearalenone

Vomitoxin in the 2020 corn crop continues to plague both livestock and grain producers. Livestock producers are trying to decide how best to manage corn and corn by-products with high levels of vomitoxin, and those who grow corn are trying to decide how best to avoid vomitoxin contamination in 2021.

In the 15 minute video below, OSU Extension Educations John Barker, Rob Leeds, and Jacci Smith discuss where and why this year’s vomitoxin issues originated, considerations for avoiding problems in coming years, how it impacts livestock, and what’s involved in testing grain for vomitoxin.

Projected Returns for 2021 – Increasing Fertilizer Prices May Force Tough Decisions

From Barry Ward and John Barker

The profit margin outlook for corn, soybeans, and wheat is relatively positive as planting season approaches. Prices of all three of our main commodity crops have moved higher since last summer and forward prices for this fall are currently at levels high enough to project positive returns for 2021 crop production. Recent increases in fertilizer prices have negatively affected projected returns. Higher crop insurance costs, as well as moderately higher energy costs relative to last year, will also add to overall costs for 2021.

Production costs for Ohio field crops are forecast to be modestly higher compared to last year with higher fertilizer, fuel, and crop insurance expenses. Variable costs for corn in Ohio for 2021 are projected to range from $386 to $470 per acre depending on land productivity. Variable costs for 2021 Ohio soybeans are projected to range from $216 to $242 per acre. Wheat variable expenses for 2021 are projected to range from $166 to $198 per acre. Continue reading

Did you miss out on our Ohio State University Corn or Soybean College?

Did you miss out on the Ohio State University Extension Corn or Soybean College on February 11th? We have an opportunity for you to rewatch the recordings.  The recordings are broken down into topics and smaller sections. If you are having any problems viewing, please reach out to me.

The recorded presentations up on our Ohio State Ag Crops YouTube Channel:

Pierce Paul summarized the Q&A portion of his session in the Corn Newsletter last week. You can access that summary here.

Grain Test Weight Considerations for Corn

R.L. (Bob) Nielsen
Agronomy Dept., Purdue Univ.
West Lafayette, IN 47907-2054
Email address: rnielsen at purdue.edu
Twitter: @PurdueCornGuy

Among the top 10 most discussed (and cussed) topics at the Chat ‘n Chew Cafe during corn harvest season is the grain test weight being reported from cornfields in the neighborhood. Test weight is measured in the U.S. in terms of pounds of grain per volumetric “Winchester” bushel. In practice, test weight measurements are based on the weight of grain that fills a quart container (37.24 qts. to a bushel) that meets the specifications of the USDA-AMS (FGIS) for official inspection (Fig. 1). Certain electronic moisture meters, like the Dickey-John GAC, estimate test weight based on a smaller-volume cup. These test weight estimates are reasonably accurate but are not accepted for official grain trading purposes.

The official minimum allowable test weight in the U.S. for No. 1 yellow corn is 56 lbs/bu and for No. 2 yellow corn is 54 lbs/bu (USDA-AMS (FGIS), 1996). Corn grain in the U.S. is marketed on the basis of a 56-lb “bushel” regardless of test weight. Even though grain moisture is not part of the U.S. standards for corn, grain buyers pay on the basis of “dry” bushels (15 to 15.5% grain moisture content) or discount the market price to account for the drying expenses they expect to incur handling wetter corn grain.

Growers worry about low test weight because local grain buyers often discount their market bids for low test weight grain. In addition, growers are naturally disappointed when they deliver a 1000 bushel (volumetric bushels, that is) semi-load of grain that averages 52-lb test weight because they only get paid for 929 56-lb “market” bushels (52,000 lbs ÷ 56 lbs/bu) PLUS they receive a discounted price for the low test weight grain. On the other hand, high test weight grain makes growers feel good when they deliver a 1000 bushel semi-load of grain that averages 60 lb test weight because they will get paid for 1071 56-lb “market” bushels (60,000 lbs ÷ 56 lbs/bu). Continue reading

Gibberella Ear Rots Showing up in Corn: How to Tell It Apart from Other Ear Rots

Author(s): Pierce PaulFelipe Dalla Lana da Silva

Over the last two weeks, we have received samples or pictures of at least two different types of corn ear rots – Gibberella and Trichoderma. Of the two, Gibberella ear rot (GER) seems to be the most prevalent. Ear rots differ from each other in terms of the damage they cause (their symptoms), the toxins they produce, and the specific conditions under which they develop. GER leads to grain contamination with mycotoxins, including deoxynivalenol (also known as vomitoxin), and is favored by warm, wet, or humid conditions between silk emergence (R1) and early grain development. However, it should be noted that even when conditions are not ideal for GER development, vomitoxin may still accumulate in infected ears.

A good first step for determining whether you have an ear rot problem is to walk fields between dough and black-layer, before plants start drying down, and observe the ears. The husks of affected ears usually appear partially or completely dead (dry and bleached), often with tinges of the color of the mycelium, spores, or spore-bearing structures of fungus causing the disease. Depending on the severity of the disease, the leaf attached to the base of the diseased ear (the ear leaf) may also die and droop, causing affected plants to stick out between healthy plants with normal, green ear leaves. Peel back the husk and examine the suspect ears for typical ear rot symptoms. You can count the number of moldy ears out of ever 50 ears examined, at multiple locations across the field to determine the severity of the problem.

Ear rot symptoms

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Do your Ears Hang Low? – Premature Ear Declination in Corn

Collapsed ear shank of droopy ear

Collapsed ear shank of droopy ear

Taken from Purdue Extension, Chat and Chew Cafe – September 11, 2020 – Issue 2020.24 – By Bob Nielson

Droopy ears are cute on certain breeds of dogs, but droopy ears on corn plants prior to physiological maturity are a signal that grain fill has slowed or halted. Ears of corn normally remain erect until some time after physiological maturity (black layer development) has occurred, after which the ear shanks eventually collapse and the ears decline or “droop” down. The normal declination of the ears AFTER maturity is desirable from the perspective of shedding rainfall prior to harvest and avoiding the re-wetting of the kernels. PREMATURE ear declination, however, results in premature black layer formation, lightweight grain, and ultimately lower grain yield per acre.

What Causes Premature Droopy Ears? The most common contributing factor is severe drought stress that extends late into the grain-filling period. I have seen droopy ears in quite a few fields around Indiana these past few weeks in areas afflicted with severe drought stress. Even though Indiana has not experienced a lot of excessively hot (≥ 95o F) days in 2020, drought conditions coupled with sunny days and unusually low humidity (i.e., low dew point temperatures) result in significant evapotranspiration demands on the crop during grain filling. In most of the affected fields, the severity of leaf rolling and premature leaf death (senescence) due to drought stress was also high. Continue reading

Tar Spot – What is it?

Figure 2. Tar spot symptoms on leaves both on the lower and the upper canopy. (Photo Credit: Darcy Telenko)

While I have been out in Paulding county scouting in the last week, I have not noticed any tar spot in our cornfields as of yet.  It could be there though as I am not walking in every field. I wanted producers to take note of what Tar Spot looks like and some monitoring from our neighbors in Indiana and information from a previous CORN New Article.  Continue reading

Potential for Nitrate Problems in Drought Stressed Corn

Have very dry soil conditions increase the potential for toxic levels of nitrates in corn harvested for silage? Nitrates absorbed from the soil by plant roots are normally incorporated into plant tissue as amino acids, proteins, and other nitrogenous compounds. Thus, the concentration of nitrate in the plant is usually low. The primary site for converting nitrates to these products is in the growing leaves. Under unfavorable growing conditions, especially drought, this conversion process is slowed, causing nitrate to accumulate in the stalks, stems, and other conductive tissue. The highest concentration of nitrates is in the lower part of the stalk or stem. For example, the bulk of the nitrate in a drought-stricken corn plant can be found in the bottom third of the stalk. If moisture conditions improve, the conversion process accelerates, and within a few days, nitrate levels in the plant return to normal. Continue reading

Corn Silage Harvest Timing

The milk-line of on these ears is about one-fourth to one-third down the kernel. This stage might be about right for oxygen-limited silos but could be too late for conventional tower or bunker silos.

Silage harvest has begun in some parts of Ohio. Proper harvest timing is critical because it ensures the proper dry matter (DM) concentration required for high-quality preservation, which in turn results in good animal performance and lower feed costs. The proper DM concentration is the same whether it is a beautiful, record-breaking corn crop or a severely drought-stressed field with short plants containing no ears.

The recommended ranges for silage DM are:

Bunker: 30 to 35%

Upright: 32 to 38%

Sealed upright 35 to 40%

Bag: 32 to 40%

Chopping corn silage at the wrong DM concentration will increase fermentation losses and reduce the nutrient value of the silage.  Harvesting corn too wet (low DM concentration) results in souring, seepage, and storage losses of the silage with reduced animal intake. Harvesting too dry (high DM concentration) promotes mold because the silage cannot be adequately packed to exclude oxygen. Harvesting too dry also results in lower energy concentrations and reduced protein digestibility. Continue reading

Corn Smut in my Fields

Last week on our Coffee Talk, we had a producer talking about Corn Smut.  Today, as I listened to the Michigan State virtual breakfast, they were talking about Corn Smut also.

Here is a little bit of information about Corn Smut from Peter Thomlison, retired Corn Specialist from OSU.

Corn Smut

Source: P. Thomison, OSU

Common Corn Smut in-ears at R5   Source: P. Thomison, OSU

Source: P. Lipps, OSU Plant Pathology

Source: P. Lipps, OSU Plant Pathology

Symptoms: The smut gall is composed of a great mass of black, greasy or powdery spores enclosed by a smooth white covering of corn tissue. The gall may be 4-5 inches in diameter. The corn plant may be infected by smut at any time in the early stages of growth, but becomes less susceptible after the formation of the ear. Above-ground parts may be infected, but it is more common to see the smut galls on the ears, tassels, and nodes than on the leaves, internodes, and brace roots. After the spores mature, the covering becomes dry and brittle, breaks open, and the spores sift out. Greatest yield losses occur when the ear becomes infected or if the smut gall forms on the stalk immediately above the ear. Common corn smut is not associated with mycotoxins. In Mexico, immature smut galls are consumed as an edible delicacy.

Cause: Corn smut is caused by the fungus, Ustilago zeae, that survives as a resistant spore over winter, and possibly for 2 to 3 years in the soil. These spores can be blown long distances with soil particles or carried into a new area on unshelled corn and in manure from animals that fed on infected corn stalks. Spores germinate in rainwater that has collected in the leaf sheaths. This leads to infections that are visible in 10 days or more. Wounds from various injuries (including hail, wind, and insects) provide points for the fungus to enter the plant.

The smut fungus is sensitive to temperature and moisture changes. In a warm season, the amount of smut is related closely to the amount of moisture in the soil, especially during June. When temperatures are lower than normal, there may be little smut even though soil moisture may be high.

Management: Seed treatment is of no value for smut control because few spores are on the corn seed.

Spraying for corn borer control helps in cases when insect populations are high. Avoid injury of roots, stalks, and leaves during cultivation. Tillage to bury diseased corn stalks in the fall will help give some control.

References: White, Donald G. (ed.). 1999. Compendium of Corn Diseases (3rd Edition). APS Press, The American Phytopathological Society.

Making Corn Silage in Dry Conditions

The primary goal of making corn silage is to preserve as many nutrients in the corn plant as possible, to produce a feed that is acceptable to cows, and to minimize any risks associated with feeding the silage.  The following are important considerations for making corn silage when growing conditions have been dry.

Chop at the correct dry matter concentration (Editor’s note: see the accompanying article “Corn Silage Harvest Timing”). Drought-stressed corn plants are often much wetter than they appear, even if the lower plant leaves are brown and dried up.  Before starting chopping, sample some plants (cut at the same height as they will be with the harvester) and either analyze DM using a Koster tester or microwave or send it to a commercial lab (turn-around time may be a few days if you send it to a lab).  If the plants are too wet, delay chopping until the desired plant DM is reached.  The plant may continue to accumulate DM (increase yield), and you will not suffer increased fermentation losses caused by ensiling corn that is too wet. Continue reading

The Ohio Crop Tour Goes Virtual

This article originally appeared in Ohio’s Country Journal and Ohio Ag Net

Due to the COVID-19 pandemic, the Ohio Ag Net and Ohio’s Country Journal crop tour is moving to a virtual experience for 2020! We are inviting growers from across Ohio to send in their yield data using the form below. This data will be posted completely anonymously, however, we are asking you to enter your contact information to be eligible for a drawing for a $500 gift card to Rural King. Each field entry is another entry for the drawing.

Worksheets

Print our handy worksheets to help you with your calculations and to take notes in the field! You are free to make as many copies as you would like.

Click to download the corn worksheet.

Click to download the soybean worksheet.

Click to submit your data.

Revisiting Corn Use for Ethanol

By: Todd Hubbs, Department of Agricultural and Consumer Economics, University of Illinois.  farmdoc daily (10):133

Stronger export numbers and lower acreage boosted corn prices since the end of June.  Concerns about demand weakness in ethanol production emerged recently.  A recovery in economic activity helped ethanol plants ramp up production as gasoline demand increased.  A resurgence in virus incidences threatens ethanol production over the short run and injects uncertainty into long-run prospects.

Gasoline demand recovered to almost 89 percent of pre-coronavirus lockdown levels in early July.  Despite this positive development, the recovery in demand flattened out over the last few weeks.  Gasoline stocks began to recede but still sit substantially above levels seen at this time of the year.  Attempts to reopen the economy hit a snag as the virus spread rapidly around the country after initial hopes saw a rapid opening in many areas.  At 8.648 million barrels per day, demand recovered substantially from the low point of 5.311 million barrels per day seen in early April.  The path back to normal gasoline demand levels appears stalled.  Ethanol production followed this recovery and will feel the implications of flattening gasoline use. Continue reading

Drought Projections Do Not Go Well With Fungicide Applications

By Anne Dorrance and Pierce Paul, CORN Newsletter

Several calls this past week for fungicide applications on corn and soybean at all different growth stages.  So let’s review what might be at stake here.

Soybeans.  Frogeye leaf spot and white mold on susceptible varieties when the environment is favorable for disease easily pay the cost of application plus save yield losses.  Let’s dig a bit deeper.  Both of these diseases are caused by fungi but the frogeye leaf spot is a polycyclic disease, meaning that multiple infections occur on new leaves through the season while the white mold is monocyclic and the plant is really only susceptible during the flowering stage.  Both of these diseases are also limited geographically in the state.  White mold is favored in North East Ohio and down through the central region where fields are smaller and airflow can be an issue.  Frogeye has been found on highly susceptible varieties south of 70, but it is moving a bit north so it is one that I am watching.

White mold is also favored by a closed canopy, cool nights, and high relative humidity.  So farmers in these areas should double-check their variety ratings first.  If it is moderate to low score for resistance (read the fine print) then this year a spray may be warranted.  We have gotten consistent control of white mold with Endura at R1.  Herbicides that are labeled for white mold suppression have also knocked back this disease, but if a drought occurs or no disease develops, losses of 10% or greater can occur due to the spray alone.  For these purposes, R1 is a flower on the bottom of 1/3 of the plants in the field. Continue reading