More on Tar Spot: Mid to Late R-Stage Fungicide Application

Most of the corn across the state of Ohio is now between the late-R1 (silking) and late-R3 (milk) growth stages, with a few late-planted fields at late vegetative stages. Concerns about tar spot, but more likely, a sense of security provided by relatively high grain prices have led to several fields being sprayed with a fungicide at or shortly after R1 and questions being asked about spraying additional fields that are now at mid reproductive stages (between late-R2 [kernel blister] and R3 [milk]) of development. Concerns about tar spot are understandable, given how widespread the disease was last year (2021) and the level of damage it is capable of causing. However, the basic approach for tar spot management in Ohio should be no different from the approach commonly recommended for managing other, more common foliar, fungal diseases such as gray leaf spot. You have to scout fields, monitor the weather, and if needed, apply the fungicide when it is most likely to be effective, without violating label restrictions.

So far this season, of the more than 15 samples examined (actual leaves or images) and 40+ field scouted at 15-day intervals, only three were positive for tar spot. This is considerably lower than what we saw at a similar time and growth stage in 2021. Does this mean that your R2-R3 corn is no longer at risk for tar spot? In places where the disease is endemic (hot spots where lots of spores may be readily available), a susceptible hybrid is planted, and weather conditions are favorable (moderate temperatures and wet and humid), tar spot may still develop and spread quickly after R3. However, under conditions less favorable for tar spot development (cool and dry) where spores need to blow in from outside, the crop is at lower risk for tar spot, even if symptoms begin to develop at R3. So, the short answer is, if you planted a susceptible hybrid no-till or minimum-till in a corn field that had tar spot last year, and weather conditions become highly favorable over the next few weeks, your crop could still be at risk.

Continue reading

Hail Damage to a Maturing Corn Crop

Hail damage occurred in a few Knox County fields after this past weekend’s (August 20 & 21) round of storms.  Some of you  have asked about the damage potential caused by these storms.

The following information can be found in Evaluating Hail Damage to Corn from the University of Nebraska.  https://extensionpublications.unl.edu/assets/pdf/ec126.pdf

Yield losses can occur from stand reduction, defoliation, and direct damage to the ear itself.  The fields I looked at were in the soft dough to “very” early dent stages.  Table III below shows the anticipated damage due to defoliation.

Table III. Estimated percent corn yield loss due to defoliation occurring at various stages of growth.”

Reprinted from the Com Loss Adjustment Standards Handbook FCIE-2508 (11-2009) 2010 and Succeeding Crop Years, National Crop Insurance Services. This system counts a leaf as fully developed when the leaf tip points to the ground (not fully developed collar).

To estimate total yield loss, consider the following example:

An early August hail storm strikes corn at the soft dough stage. There is defoliation and severe bruising of the ears. The defoliation is calculated at 90 percent.

  1. Ten ears are stripped of their husks and the row number and kernels/row are counted. There are approximately 300 kernels per ear, and on average 30 of these are bruised. This 10 percent direct damage is subtracted from 100 percent, as in the first example with stand reduction.
  2. Defoliation yield reduction ( Table III) for the remaining 90 percent at soft dough is 35 percent.
  3. To calculate yield loss at this point the 10 percent from direct damage is subtracted ( 100 – 10 = 90 percent). The remaining 90 percent is multiplied by 35 percent (90 x 0.35 percent loss). The result is 31.5 percent defoliation loss. The total loss would be from direct damage (10 percent) and defoliation loss (31.5 percent) for a total of 41.5 percent.

This is only an estimate of the percent yield loss. As with undamaged corn, extremely favorable weather during the rest of the growing season can cause actual yields to be higher than expected. Likewise, unfavorable weather can cause greater than anticipated reductions.

Tar Spot Of Corn: What To Know And New Research

by: Dan Quinn and Darcy Telenko, Purdue University

Due to its relatively recent U.S. discovery and its ability to cause significant production and economic losses, tar spot is often a topic of angst and anxiety amongst corn farmers and agronomists in Indiana. For example, a severely infected field can reach yield losses upwards of 60 bushels per acre! Yield losses are often a result of reduced photosynthetic capacity (green leaf area) of the corn plant during grain fill resulting in poor grain fill, kernel abortion, and reduced kernel weight. In addition, severe infection can reduce corn stalk integrity and cause significant lodging later in the season. Tar spot was first confirmed in northwest Indiana in 2015 and the first significant yield-reducing event of the disease was observed in 2018. Similarly, severe outbreaks and large areas of infection of this disease were observed in Indiana in 2021. Tar spot is caused by the fungus known as Phyllachora maydis and can be identified by small, raised black and circular spots present on corn leaves, stalks, and husks (Figure 1). These black and circular spots are known as fungal fruiting structures called stromata, each of which can produce thousands of spores. Overall, tar spot infection and severity can vary based on environmental conditions, the total amount of the pathogen present in the field, and corn hybrid chosen.

What Conditions Cause Tar Spot? Continue reading

Evaluating the Prevent Plant Option

By: Eric Richer & Chris Bruynis, OSU Extension Educators

Planting progress goes differently every year and in each part of the state. This year is no different in Ohio. Some places got in early and are finished. Others had their ‘normal’ planting progress with ‘normal’ Mother Nature breaks, perhaps with some re-plant needed. And still others have not had ideal conditions all spring to plant.  As such, we have received some recent calls regarding the mechanics and economics of utilizing the Prevent Plant through crop insurance this year in certain parts of the state. First and foremost, we are not crop insurance agents, so speaking with your agent is of utmost importance. In this article, we will walk through an example on the economics of electing Prevent Plant.

In Ohio, once you arrive at the final plant date of June 5 for corn (already passed) and June 20 for soybeans, you basically have 3 options in a corn scenario: Continue reading

Xyway Corn Fungicide Trial

Knox County Xyway Trials

Taking stand counts at our Xyway plot – Great looking field of corn!

 

 

A Special Thanks to Ed & Vicki Piar!!

 

The goal of this study is to determine corn’s response to an at-plant soil application of flutriafol (Xyway™) fungicide. Information from this trial will be used to improve corn disease management recommendations for growers throughout the state.

Vomitoxin Research 2022 – Plot #4

Knox County Vomitoxin Research Station #4 Installed – Thanks to Dr. Pierce Paul and Crew!

A Special Thanks to Braddock Farms – Jim and Susan Braddock!!

 

Fusarium molds that produce DON often develop under wet weather conditions. This particular mold initially enters plants through silks or wounds, and cool, wet conditions during the silking stage promotes spore production, increasing the inoculum load that can potentially infect more plants. Infections by the fungal species F. graminearum result in the development of Gibberella ear and stalk rots. Corn from fields with this disease issue may need to be tested for potential contamination.

The goal of this Statewide research project is to develop a prediction model that will allow producers to take corrective action based upon a weather prediction model to prevent plant infections.

40 of these research stations are scattered throughout West-Central Ohio.

Vomitoxin Research 2022 – Plot #3

Knox County Vomitoxin Research Station #3 Installed – Thanks to Dr. Pierce Paul and Crew!

A Special Thanks to Clark Farms – Tom and Nate Clark!!

 

Fusarium molds that produce DON often develop under wet weather conditions. This particular mold initially enters plants through silks or wounds, and cool, wet conditions during the silking stage promotes spore production, increasing the inoculum load that can potentially infect more plants. Infections by the fungal species F. graminearum result in the development of Gibberella ear and stalk rots. Corn from fields with this disease issue may need to be tested for potential contamination.

The goal of this Statewide research project is to develop a prediction model that will allow producers to take corrective action based upon a weather prediction model to prevent plant infections.

40 of these research stations are scattered throughout West-Central Ohio.

Vomitoxin Research 2022 – Plot #2

Knox County Vomitoxin Research Station #2 Installed – Thanks to Dr. Pierce Paul and Crew!

 

A Special Thanks to David and Emily Mitchem!!

 

Fusarium molds that produce DON often develop under wet weather conditions. This particular mold initially enters plants through silks or wounds, and cool, wet conditions during the silking stage promotes spore production, increasing the inoculum load that can potentially infect more plants. Infections by the fungal species F. graminearum result in the development of Gibberella ear and stalk rots. Corn from fields with this disease issue may need to be tested for potential contamination.

The goal of this Statewide research project is to develop a prediction model that will allow producers to take corrective action based upon a weather prediction model to prevent plant infections.

40 of these research stations are scattered throughout West-Central Ohio.

Vomitoxin Research 2022 – Plot #1

Knox County Vomitoxin Research Station #1 Installed – Thanks to Dr. Pierce Paul and Crew!

 

A Special Thanks to Sassafras Hill Farms – Nate McKee and Skyler Epler!!

 

Fusarium molds that produce DON often develop under wet weather conditions. This particular mold initially enters plants through silks or wounds, and cool, wet conditions during the silking stage promotes spore production, increasing the inoculum load that can potentially infect more plants. Infections by the fungal species F. graminearum result in the development of Gibberella ear and stalk rots. Corn from fields with this disease issue may need to be tested for potential contamination.

The goal of this Statewide research project is to develop a prediction model that will allow producers to take corrective action based upon a weather prediction model to prevent plant infections.

40 of these research stations are scattered throughout West-Central Ohio.