Three weeks ago an article was posted in VegNet outlining a relatively new disease on sweet corn, Tar Spot (https://u.osu.edu/vegnetnews/2025/03/08/tar-spot-on-sweet-corn/).

In order to understand the magnitude and distribution of this disease across Ohio, a short survey was available for growers to anonymously send in their experience with Tar Spot so that a more accurate understanding of this disease could be made, informing potential research in 2025. If you would like to add to our understanding of this disease on your farm, here is the link to follow: https://osu.az1.qualtrics.com/jfe/form/SV_d5NMkdMmASqJza6

Two growers responded to the survey from west central and north central Ohio stating they:

-have had issues with Tar Spot since at least 2023 (primarily “late” planted)
-have sprayed fungicides on the crop since at least 2023
-believe this disease is impacting ear quality and sales

As a result of this information, a group of OSU researchers and Extension educators have decided to go forward with planning a Tar Spot evaluation and yield impact study at three locations in 2025. The study will be guided by Dr. Pierce Paul, Tar Spot researcher, Professor and Chair of Plant Pathology, and Dr. Andres Sanabria Velazquez, Associate Professor in Plant Pathology. Contributing to the study design, data collection and analysis will be Dr. Logan Minter (Associate Professor in Extension, Field Specialist), Jim Jasinski (Professor in Extension), Mike Gastier and Pressley Buurma (Extension Educators).

Sites for the Tar Spot trials will be South Centers at Piketon, Western Ag Research Station (South Charleston), and Muck Crops Research Station (Willard), evaluating both fresh market and shipping sweet corn hybrids. More details of these trials will be released soon.

The past few months have been full of opportunities for growers to attend local, statewide, regional or even national fruit and vegetable conferences to learn new skills and get updates on current production and pest management practices. I recently attended a conference where Dr. Julie Kikkert, Cornell University, gave a very interesting presentation on Tar Spot in sweet corn. During her talk, gears began turning in my head as I considered if this disease was also a problem under the radar for Ohio sweet corn growers.

Crop Protection Network

Tar Spot was initially detected in Ohio in 2018 on field corn and is mostly distributed in the northwest and northcentral parts of the state (https://agcrops.osu.edu/newsletter/corn-newsletter/2020-03/tar-spot-corn). Tar Spot is currently found in 14 states and mostly thought of as a pathogen on field corn, due primarily to the length of exposure as the ear matures on the stalk. Since sweet corn is harvested immature, the question of Tar Spot impacting quality and yield seems remote but possible. Late planted sweet corn in Ohio (ca. late June or early July), is most likely to be affected but other factors such as prior crop, tillage and weather can play a part in the disease severity.

From CORN article

If the prior crop was field or sweet corn then the risk of Tar Spot increases, as does the risk if there was no primary tillage performed which could serve to bury inoculum (old, infected corn leaves).  In the later part of the season, if weather conditions turn cool and wet, this favors disease development. Proximity to large acreages of field corn may also be a factor as air borne spores can travel miles to infect other corn plants. At this time there are no resistant field or sweet corn hybrids but there may be some tolerance among hybrids. Fungicides can be applied to late planted sweet corn crops that are effective against this pathogen but the matter of economics and Pre Harvest Interval comes into play. https://cropprotectionnetwork.org/publications/fungicide-efficacy-for-control-of-corn-diseases

What can be done?

At this point, several members of the OSU Specialty Crops team are looking to set up multiple late planted sweet corn hybrid trials on OSU research stations from southern to northern Ohio to determine the extent of foliar Tar Spot infestation and if any impacts on ear production or quality can be observed.

Since this pathogen is new to Ohio sweet corn growers, we are also interested in feedback from growers who have seen this pathogen on their crop in 2024. In order to collect this information anonymously, please use the 9-question feedback form at this link: https://osu.az1.qualtrics.com/jfe/form/SV_d5NMkdMmASqJza6

 The survey questions are listed below. The last question on the form is open ended if growers have any other thoughts to share on this disease. In a few weeks, I will summarize the observations and concerns of the growers who responded.

Q1. Did you see Tar Spot on sweet corn last year?

Q2. What was the previous crop?

Q3. What tillage was performed in the field?

Q4. What was the planting date of the infected sweet corn hybrid?

Q5. When was the sweet corn harvested?

Q6. What was the name of the sweet corn hybrid?

Q7. Did the Tar Spot infection affect the ear quality in your opinion?

Q8. What county is your farm located?

Q9. Anything else to tell us about Tar Spot on your farm in 2024?

The following article was written by and all photos supplied by:

Dr. Erdal Ozkan
Professor and Extension State Specialist
Pesticide Application Technology
The Ohio State University

Once a decision is made that spraying pesticides is a must to protect your crop against weeds, insects and diseases, there are two important things you should do to get the most out of your sprayer during the spraying season. One of these important tasks should be accomplished even before the spraying season starts. It is making sure the sprayer is delivering the gal/acre application rate you expect to get from it at the travel speed you operate the sprayer. Many refer to this as “calibration” of the sprayer. The second important thing to do is to operate the sprayer properly and making appropriate adjustments to the sprayer to not waste pesticides and to make sure the pesticides are applied uniformly on the target. Let’s tackle both of these issues one at a time.

Calibrate your sprayer

A sprayer can only be effective, efficient, and safe if it’s properly checked and calibrated before it’s taken to the field, and if it’s periodically checked and calibrated during the spraying season. The primary goal with calibration is to determine the actual rate of application, and then to make the necessary adjustments if there is a difference between the actual application rate and the “expected” application rate. Under some specific circumstances the expected application rate could be the rate chosen by you, the applicator. However, usually, the “expected” application rate is what is mentioned on the chemical label and sprayer operators must follow what is recommended on the label. This required rate is most often given in “gallons per acre”. Your job as the applicator is to make sure your actual application rate matches the recommended rate on the label. You can find out how close your application rate to the label rate only by calibrating the sprayer. Although your goal should be to achieve a perfect match between the actual and the expected application rates, an error margin of less than 5% between the two rates is acceptable.

How to calibrate a sprayer?

Regardless of the sprayer used, calibration requires measuring the nozzle flow rate (gal/min) and the travel speed (miles/hour), and only three things are needed: a watch or smart phone to record the time when measuring the nozzle flow rate or the travel speed, a measuring tape, and a jar graduated in ounces.

Collecting nozzle flow rate from a boom sprayer is relatively easy because spray is directed vertically towards the ground. However, when using sprayers used in orchards and vineyards have nozzles discharging spray in a wide range of directions from close to ground vertically to horizontal and upward directed toward the crop canopy. Using milk liners to connect nozzles to the hoses inserted in collection cups is a practical way to check flow rates of nozzles without getting wet.

Please look at the Ohio State University Extension publication FABE-520 for an easy method to calibrate a boom-type sprayer.  Here is the URL for this publication:

http://ohioline.osu.edu/factsheet/fabe-520.

If you are calibrating a high pressure airblast sprayer used to apply pesticides on trees in fruit orchards, please look at the Ohio State University Extension publication FABE-537.  Here is the URL for this publication:

http://ohioline.osu.edu/factsheet/fabe-537.

Things to do prior to calibration

Before calibration, run the sprayer, inspect it for leaks, and make sure all vital parts function properly and that the sprayer has a good set of nozzles. Some nozzles or screens may become clogged causing under-application. Clean all clogged nozzles and screens before calibrating the sprayer and after each application (especially when powder sulfur or copper are applied in vineyards). Observe the spray pattern before calibration, and often during spraying to make sure there is no clogging. Nozzle wear from extended use causes over-application and/or non-uniform application. Check the flow rate of each nozzle for at least 30 seconds. Check the nozzle company catalog (website) to see what the flow rate of a new nozzle at the same pressure setting is.  Compare the flow rates of nozzles you measured with the flow rate of the new nozzles Replacing a nozzle is recommended if its measured flow rate is 10% greater than that of the new nozzle at the same spray pressure.

Follow safety rules when calibrating sprayers

For safety reasons, calibration should be done using water in the sprayer tank. A mixture containing pesticides may have a slightly higher density or viscosity than water, which may slightly reduce the flow rates of nozzles. However, usually, the difference in flow rates between water alone and a mixture containing pesticides is not significant unless a high volume of high-dense or viscous adjuvants is mixed in the spray mixture. Conversions for spray solutions with different densities are provided by the nozzle manufacturers in their catalogs or websites. Even when calibrating the sprayer using water, always wear the personal protective equipment used for spraying pesticides, such as gloves and goggles.

Other adjustments needed for effective spraying

Knowing that the actual spray application rate (gal/acre) determined through calibration matches the expected application rate (what is on the chemical label) is the first step to achieve maximum accuracy from a sprayer. However, this is only one aspect of achieving effective pest control. How much of the spray reaches the target canopy, and how uniformly it is distributed within the target canopy are two other factors that play important roles in achieving maximum protection against pests.

The goal in spraying pesticides should be landing as many droplets on the target and as uniformly throughout the canopy as possible. This is especially important when spraying fungicides and insecticides. With boom sprayers used for spraying on vegetables, there are several reasons why the deposition on the target is not uniform across the boom. Some major reasons include having different size and types of nozzles mixed on the boom, clogged nozzles and uneven boom height over the target sprayed.

Non-uniform deposition of pesticides on the target canopy is even a more serious issue to deal with. If you a fruit grower, it is very likely that the sprayer you have is like the ones shown in the following pictures.

Unfortunately, the sprayer shown on the left has two design and/or adjustment issues that significantly reduce the spray deposited on the target: 1) The top two to three nozzles on each side of the sprayer aren’t directing spray toward the targets and should be turned off. 2) There are no deflector plates, neither on the top or the bottom part of the fan, to direct the air plume towards the target. These plates that ensure that the sprayed droplets are deposited on the canopy, are present on the sprayer shown on the right.

When spraying an orchard or vineyard using an airblast sprayer, adjust the angle of the deflector plates to match the canopy’s height of the canopy. This adjustment is necessary each time spraying is conducted because the canopy height may vary from one orchard or vineyard to another, or even within the same orchard or vineyard throughout the growing season. A practical way to determine the correct trajectory of the air discharged from the fan is to tie ribbons around the area where air is exiting the fan. Then turn on the fan, watch the direction the air blows the ribbons, and adjust the angle of the deflectors accordingly.

Adjust the air flow when using airblast orchard sprayers

Air generated by the sprayer fan is what carries droplets from the nozzle to the target. Too little or too much air results in ineffective and inefficient coverage of the target. The goal is to adjust the sprayer fan air-flow rate and volume so that the air being directed into the canopy replaces the air already in the canopy, but dies down significantly as it reaches the other side of the canopy. This adjustment will result in very little spray droplets escaping the canopy. Be aware that too much air flow can force leaves together, creating a surface that blocks the passage of air. When air cannot penetrate the canopy, it moves upward in a vertical trajectory, further exacerbating the off-target movement of droplets. In general, most, if not all of today’s air-assisted or airblast sprayers, generate more air assistance than what is needed. This is especially true for vineyard spraying. So, it is very important to take the time to adjust the air stream characteristics (direction, air speed, and air flow rate) suitable for the tree or vine canopy conditions at the time of the spray applications. As a side benefit, a reduction in the airflow rate also lowers fuel consumption. 

I mentioned in this article the highlights of what you need to do to get the best performance from your sprayer. You can find detailed information on several Ohio State University Extension Fact Sheets which you can find by visiting the website for OSUE publications: https://ohioline.osu.edu. Once you are on this site, do a search using my last name (“ozkan”) as the key word for your search. You will see a listing of publications  on sprayer calibration, selecting the right size of nozzle for the intended application rate, how to achieve efficient penetration and uniform deposition of droplets inside the canopy, and how to assess the quality of spray deposition and coverage on the target.

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SWD larvae in fruit

Spotted-wing Drosophila male (L) and female (R).

If you grow a crop that has been impacted by SWD over the past decade, February 28 is your last chance to report how this insect has affected your operation.

Ohio was first infested with spotted-wing Drosophila (SWD) in the fall of 2011. This pest turned long standing IPM programs on their head and forced growers to adopt new monitoring and management practices for this pest or face losing significant amounts of  blueberries, raspberries, strawberries, blackberries, peaches and grapes to larval infestation. While OSU had an active Extension and outreach program to teach growers about this insect since discovery in Ohio, we relied on research generated by several multi-state grants to keep our growers at the forefront of IPM on susceptible crops. While we have made substantial progress on monitoring and managing this pest, there are still many research and management questions to answer. To help inform the next phase of SWD research and outreach, please consider adding your thoughts about how this pest has impacted your operation over the past decade. All responses are confidential.

**This survey is being shared with multiple mailing lists to ensure that we reach as many impacted growers as possible. We apologize if you receive it more than once!

Dear Berry Growers:

As part of a national team of entomologists studying the management of spotted-wing drosophila (SWD), we are reaching out with a request for assistance to help understand the current impacts of SWD on your farm and how these impacts may have changed in the last 10 years.

If you are willing to share insights from your farm, farms you manage, or growers you work with, please complete this short survey, which will take about 15 minutes or less: https://docs.google.com/forms/d/e/1FAIpQLSeW6rCcyM9vf_sjLJDj0J_6G03jlVbBLZt5rlX7kmzSj0Ypog/viewform

How will this information be used?
This information will be used to develop new research goals as part of a USDA Specialty Crop Research Initiative proposal under development. It will also be compared to information collected in similar surveys in 2013 and 2014 to help us understand where challenges still exist for SWD management and what improvements have been made over the last 10 years and shared in extension and scholarly publications.

Who should I contact for more information?
For more information about this survey, contact Hannah Levenson, hklevens@ncsu.edu, 919.434.7882. For more information about SWD management, contact members of our project team or your local extension expert.

Thank you,

Hannah Burrack
Professor & Chair
Department of Entomology
Michigan State University
burrackh@msu.edu

The Ohio State University South Centers is bringing its Ohio Berry Production Series to an online virtual format to reach even more growers in Ohio and beyond! Join us on February 20 beginning at 9:30 a.m. for this FREE online event via the Zoom communications platform.

This webinar will feature information to benefit both beginner and advanced growers, and to teach you proven techniques to maximize production and quality in your plantings and vineyards.

Schedule

9:30-10:30 a.m. Growing Blueberries in Ohio

10:45–11:45 a.m. Raspberry Growing in Ohio

Break for lunch

1:15-2:30 p.m. Growing Grapes in Ohio

Simply visit the link below and fill out the registration form. We also plan on offering on-demand recordings afterward, so you can access the event on-demand, as we know this fits some people’s schedules better.

 Register here: go.osu.edu/ohioberries

For even more information, consult the attached flyer.

Looking forward to seeing you virtually this year!

SWD larvae in fruit

Spotted-wing Drosophila male (L) and female (R).

If you grow a crop that has been impacted by SWD over the past decade, February 28 is your last chance to report how this insect has affected your operation.

Ohio was first infested with spotted-wing Drosophila (SWD) in the fall of 2011. This pest turned long standing IPM programs on their head and forced growers to adopt new monitoring and management practices for this pest or face losing significant amounts of  blueberries, raspberries, strawberries, blackberries, peaches and grapes to larval infestation. While OSU had an active Extension and outreach program to teach growers about this insect since discovery in Ohio, we relied on research generated by several multi-state grants to keep our growers at the forefront of IPM on susceptible crops. While we have made substantial progress on monitoring and managing this pest, there are still many research and management questions to answer. To help inform the next phase of SWD research and outreach, please consider adding your thoughts about how this pest has impacted your operation over the past decade. All responses are confidential.

**This survey is being shared with multiple mailing lists to ensure that we reach as many impacted growers as possible. We apologize if you receive it more than once!

Dear Berry Growers:

As part of a national team of entomologists studying the management of spotted-wing drosophila (SWD), we are reaching out with a request for assistance to help understand the current impacts of SWD on your farm and how these impacts may have changed in the last 10 years.

If you are willing to share insights from your farm, farms you manage, or growers you work with, please complete this short survey, which will take about 15 minutes or less: https://docs.google.com/forms/d/e/1FAIpQLSeW6rCcyM9vf_sjLJDj0J_6G03jlVbBLZt5rlX7kmzSj0Ypog/viewform

How will this information be used?
This information will be used to develop new research goals as part of a USDA Specialty Crop Research Initiative proposal under development. It will also be compared to information collected in similar surveys in 2013 and 2014 to help us understand where challenges still exist for SWD management and what improvements have been made over the last 10 years and shared in extension and scholarly publications.

Who should I contact for more information?
For more information about this survey, contact Hannah Levenson, hklevens@ncsu.edu, 919.434.7882. For more information about SWD management, contact members of our project team or your local extension expert.

Thank you,

Hannah Burrack
Professor & Chair
Department of Entomology
Michigan State University
burrackh@msu.edu