Researchers develop phone app to assess scale of vineyard disease

It will do so by making it easier to visually assess the grape and wine sector’s most costly disease, powdery mildew, according to the app’s developers at the University of Adelaide.

Supported by Wine Australia as part of a wider research project to establish objective measures for quantifying powdery mildew, PMapp was designed in close consultation with viticulturists to reduce losses that add up to the tens of millions of dollars each year, says Eileen Scott, a plant pathologist, who led the project.

“Powdery mildew is a serious disease of grapevines worldwide and, in Australia, has an estimated annual cost of $76 million through yield loss and the cost of control​,” she said.

“It causes serious quality issues with bad flavours and aromas in wine and we’ve seen that with small amounts of the surface area of Chardonnay bunches affected by powdery mildew there is an oily ‘mouth-feel’ in the resulting wine​.

“The wine sector therefore has a very low tolerance of powdery mildew on grapes with downgrading at 3–6% or rejection when disease is more severe. This is a costly disease for the grape and wine community​.”

Yet, though it is ubiquitous, powdery mildew is hard to assess as its symptoms can be difficult to see, or easily confused with dust or spray residue.
Professor Scott says that the Papp app can record of the severity and incidence of powdery mildew in a vineyard by assessing infection levels.

By matching a bunch of grapes with a computer generated image, the app allows wine growers to quickly estimate how much of the surface area it covers.
It then calculates the proportion of the bunches affected and the severity, and reports the data in a spreadsheet for analysis.

A key reference of images built into the app also helps wine growers to become familiar with the various disease patterns and severities. A website to support the app is currently being developed and is scheduled for release this month.