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Leaf doctor makes the rounds

The Leaf Doctor app analyzes a photograph of a damaged leaf or fruit and quantifies the percentage and severity of disease visible, making assessment in the field more convenient and accurate. This composite image shows screenshots of the app.

Some Android users have been wondering, is there a leaf doctor in the house?

The answer is a resounding yes.

Leaf Doctor is a free app developed by Sarah Pethybridge, assistant professor of plant pathology in the School of Integrative Plant Science, and Scot Nelson of the University of Hawaii at Manoa. The tool analyzes a photograph of a damaged leaf or fruit and quantifies the percentage and severity of disease visible. By downloading this tool to a smart phone, researchers and extension agents can use it conveniently in the field.

The app was first introduced in 2015 on iPhones, iPads and iPods, while the Android version has been in development. Now Samsung, Google and LG phone owners can download the app from Google Play.

To use Leaf Doctor, users take a photo of a leaf or part of a diseased plant, then use software to put a black background behind the image and import the photo into the app. The user then interactively selects up to eight healthy areas on the leaf. The app finds and clearly distinguishes diseased areas in blue and can provide an accurate percentage of the surface area that is diseased.

“This is a reliable way to get actual percentages of disease severity,” by comparing pixels covered by disease and pixels covered by healthy tissue, Pethybridge said.

The approach used by Leaf Doctor is also extended within the Cluster app, also developed by Pethybridge and Nelson. Available for Mac desktop computers, the program quantifies spatial patterns using photographs, such as a diseased field or landscape features in ecology.