Poster Presentation Science Protecting Plant Health 2017

Digital tools to facilitate assessing powdery mildew on grape bunches (#231)

Eileen S Scott 1 , Robert W Emmett 2 , Warren Birchmore 3 , Wade Perry 4 , Tijana Petrovic 1 , Olena Kravchuk 1 , Timothy Zanker 1 , Katherine J Evans 5
  1. School of Agriculture, Food and Wine, The University of Adelaide, Urrbrae, SA, Australia
  2. Horticultural Pathology Research, RW Emmett Pty Ltd, Mildura, Victoria, Australia
  3. Accolade Wines, Reynella, SA, Australia
  4. Lemur Software, Adelaide, SA, Australia
  5. Tasmanian Institute of Agriculture, University of Tasmania, Hobart, Tasmania, Australia

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 computer-generated 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.