2023 Scouting App to Report Tar Spot of Corn in Pennsylvania

By Miranda DePriest

On July 19th, we received our first report of tar spot of corn from Berks County. This report was two days ahead of the first one received in 2022. The severity was very low but matches our current recommendations to commence scouting corn fields for this disease in early-to-mid July. To increase the ease of reporting tar spot finds in Pennsylvania, we created a simple app using Epicollect5, available on Android and iOS platforms. This tool was developed from a new scouting app and platform we are developing for corn and soybean that will launch fully in 2024. This has some advantages over our current system in that you can use the app while scouting with our without a signal, meaning that if you are offline, the report will upload once you have connectivity. 

Below, we outline the steps you must follow to submit a report. We developed this to be systematic using a series of simple questions or information that is requested. We want to emphasize that while we ask for GPS coordinates, these are only used to identify the county where the observation was made.

Steps to use the "Corn tar spot" tool in Epicollect5.

1. Download "Epicollect5" following the app tool based on your phone or tablet type.
2. Once downloaded, open Epicollect5 and select "+ Add Project."
3. Search for the project using "Corn tar spot."
4. Select "Corn tar spot" to open the project.
5. Identify the field location by selecting "Update location."
6. Indicate the corn growth stage.
7. Indicate if tar spot is present. If you are unsure if you have tar spot, select that option, and information will be provided about what to look for to help determine if you think you have this in your field. If you are still unsure at this stage, please mark "yes," but provide an image.

Provide an estimate of the incidence or severity of the disease. If you use this for incidence, the value would be for the number of plants with tar spot divided by the number of plants examined (i.e., 10 plants with tar spot divided by 100 plants examined = 10% or a 1 in a 1-10 scale). For severity, this would be the area of the leaf covered by tar spot symptoms, and you should examine multiple leaves in the field to estimate the average severity on the same 1-10 scale.

If you have any questions about using the app, please get in touch with Miranda DePriest at mnd20@psu.edu. For information about identifying tar spot and our current recommendations for managing this disease, please contact Alyssa Collins (aac18@psu.edu) or Paul Esker (pde6@psu.edu).