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?