Tarspotter App Could Help Shield Corn from a Tar Spot Invasion

“This is the earliest we’ve reported tar spot in Iowa,” says Robertson, Iowa State professor of plant pathology. She says the early detection could be due to the Tarspotter app. Here’s how it works.

By Jenna Hoffman

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July 07, 2023 01:31 PM

“This is the earliest we’ve reported tar spot in Iowa,” says Robertson, Iowa State professor of plant pathology. She says the early detection could be due to the Tarspotter app. Here's how it works. — “This is the earliest we’ve reported tar spot in Iowa,” says Robertson, Iowa State professor of plant pathology. She says the early detection could be due to the Tarspotter app. Here’s how it works.

Tar spot robbed several key corn-producing states of upwards of 60 bushels per acre in severely infected fields in 2022, according to Purdue University Extension. The Midwest could be on a similar trajectory this year, as Integrated Pest Management (IMP) flagged Missouri, Kansas and Iowa cornfields with tar spot two weeks ago.

“This is the earliest we’ve ever reported tar spot in Iowa—10 days earlier than usual, to be exact,” says Alison Robertson, Iowa State University professor and Extension field crop pathologist.

This year’s early detection could be due to more extensive scouting and the Tarspotter app, according to Robertson.

What is the tarspotter app?

Research shows tar spot can be predicted based on multiple factors, including weather. With this in mind, the University of Wisconsin-Madison’s Integrated Pest and Crop Management (IPCM) program developed the Tarspotter app to assist farmers in making management decisions for tar spot during the V8 to R4 growth stages—the critical management window, according to the university.

Growers can forecast risk of an outbreak in a given field by inputting site-specific data into the app. Tarspotter combines the grower’s field data with its research models and GPS weather information, including temperature, dewpoint, humidity and precipitation to recommend the best treatment window.

How the tarspotter app works

Upon downloading the app on a tablet or phone, tarspotter will request information, including a field name and GPS coordinates. Next, the app will generate a risk level—inactive, low, medium or high—for the selected field.

All forecast history for each field is saved within the app. The IPCM recommends consulting the app each week to monitor the risk, as a high-risk scenario can develop rapidly.

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