Monitoring
Early detection is important to reduce disease development.
Where to monitor
- vineyard areas where the disease has been present in previous seasons;
- vines that have had flag shoots the previous year tend to produce more flag shoots due to the level of infection in the past;
- sheltered areas or densely shaded vines;
- most susceptible varieties; and
- ends of rows that may have been unsprayed.
When to monitor
Budburst onwards at two weekly intervals, bearing in mind that:
- flag shoots are most readily evident two to eight weeks after budburst before the canopy becomes too large;
- flag shoots are generally delayed in budburst compared to healthy shoots; and
- ascospore infections occur mostly on lower leaves of the shoots.
How to monitor
Some things to consider when monitoring include:
- inspect 200 vines from both sides of the row, examining leaves and later bunches;
- powdery mildew is easier to see when leaves are orientated at an angle to the sun;
- use a 10x hand lens to check suspect vine material for hyphae and conidiospores early in the season and chasmothecia later in the season; and
- mark flag shoot locations and infection sites with flag tape to enable later assessments of disease spread and effectiveness of management options.
If you are unusure whether you have powdery mildew samples can be submitted to a pathology lab for confirmation from DDLS - Plant pathology services.