University of Tasmania

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Digital tools to facilitate assessing powdery mildew on grape bunches

conference contribution
posted on 2023-05-24, 18:11 authored by Scott, ES, Powell, S, Evans, K, Barry, K, Petrovic, T, Kravchuk, O, Zanker, T, Katherine EvansKatherine Evans

Powdery mildew can affect wine quality so Australian wineries often use a threshold of 3-5% disease severity on bunches near harvest to support decisions about grape quality and price. The quality of visual assessment in the vineyard reflects the experience and training of assessors in recognising disease and estimating bunch surface affected. A free application (PMapp) for Apple and Android devices was developed to facilitate assessment of powdery mildew in vineyards and promote uniformity of assessment practices. PMapp comprises an assessment screen for entry of severity scores, a reference set of computer-generated images to support area assessment, a self-calibration tool for the user to check his/her accuracy and a diagrammatic key with 2% increments in the range 2-12%. Since release in Australia in December 2015 and globally in November 2016, PMapp has been downloaded over 2000 times.

A website developed to support use of PMapp ( offers a stepwise guide to in-field assessment, with links to training in disease recognition and area assessment and to the diagrammatic key. The disease recognition module comprises photographs of grape bunches at veraison and close to harvest; each is presented in triplicate, with different areas outlined that might represent surface with powdery mildew. The user selects the image that has powdery mildew outlined most correctly. The area assessment module allows the user to test his/her ability to assess bunch surface area affected on computergenerated images coloured to indicate powdery mildew. Results are presented as a chart showing agreement of estimate with actual image, repeatability and time taken per image. The user can access results of his/her previous attempts.

Feedback from wine sector representatives indicates that these resources have improved the quality of in-field disease assessment. PMapp is also being used in assessing bunch rot on grapes and diseases of various crops.


Wine Australia


Publication title

21st Australasian Plant Pathology Society Biennial Conference: Science Protecting Plant Health




Tasmanian Institute of Agriculture (TIA)


Australasian Plant Pathology Society

Place of publication


Event title

21st Australasian Plant Pathology Society Biennial Conference: Science Protecting Plant Health

Event Venue

Brisbane, Australia

Date of Event (Start Date)


Date of Event (End Date)


Repository Status

  • Restricted

Socio-economic Objectives

Wine grapes

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    University Of Tasmania


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