Late Blight Fungicide Application Tool for Delaware Now Online

Nathan Kleczewski, Extension Specialist – Plant Pathology;

Kevin Brinson and I worked with Bill Fry and Ian Small at Cornell to develop a late blight fungicide application tool for Delaware. The tool is for use after fungicide applications have begun to tomatoes and potatoes, and helps you determine when another application should take place given weather conditions, previous applications, and cultivar susceptibility. The permanent link to the landing site can be found here: You can also access the site from my Field Crop Plant Pathology Page, which I discussed last week

When you click on the link you are taken to a landing page. On this page you will see links to tomato and potato links at several locations in Delaware. I am working on updating the names of some of the stations, which should be completed within a few days.


A portion of the main landing page from the late blight Decision Support System.

Click on the location nearest your farm or field. This will take you to a report. A portion of the report is below. Reports are generated each day for all sites.


The tool is easy to use. Simply choose your chemical, your cultivar, and last application date, the tool shows you estimated next day for application. If the weather seems conducive to an accumulation of disease severity units within a 72 hour period (thereby increasing disease risk) the dates will turn red in the report. Simple, quick, and hopefully something you can use to help you with your disease management in tomatoes and potatoes.

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