Monitoring

Effective management of downy mildew starts with careful monitoring of the vineyard looking for infections triggered by favourable weather conditions. Collaboration between local growers will increase the chance of spotting primary outbreaks and enable coordinated management programmes.

Monitoring every 7 - 10 days when weather conditions are favourable at 2 - 3 weeks after budburst or at 10cm shoot length.

Choosing a representative site examine 200 vines concentrating on leaves near to the ground stopping momentarily at each vine looking for oil spots on the top of the leaf and white down on the underside. Part dense canopies and use a hand lens to examine suspect leaves. Record location of suspected infections. Keep moving and scan up and down. Remember primary infections may be as low as low as 1-3 oil spots per 50m of canopy making detection difficult.

The Bag Test

Use this procedure to determine whether a suspect leaf is infected and oil spots are active. Moisten the inside of a plastic bag, Places leaf or bunches inside and store overnight in a dark place at 20° - 25°C. The next morning white down will be visible on infected tissue.

Other simple measures to provide early warning of a downy mildew infection include:

  • Puddle shoot – a shoot tied down into a puddle.
  • Monitor an area of unsprayed canopy in a damp humid part of the vineyard
  • Retain a number of water shoots near ground level, these will show early sign of infection.

IPM Disease Monitoring Stations

The development of Decision Support Systems (DSS) and expert disease modelling systems (DMODEL) has lead to accurate downy mildew disease risk forecasting using temperature, humidity, precipitation, wind speed and leaf wetness data provided by small scale vineyard weather stations remotely linked to disease modeling software.