Measuring Psa weather risk online

25 January 2018

Developed as a weather-based decision support system, the online Psa Risk Model helps growers with orchard management in a Psa environment. It includes actual weather station data and weather forecast details to provide disease information and interpretations.

Recently, we’ve had a few calls asking for clarification about the low Psa risk forecast by the model.

Risk is influenced by both temperature and wetness. Where temperatures are above 20 degrees infection is unlikely (based on the Psa growth model research) so the model has often recorded light risk, even during days of rain. The online model has been checked by experts and has been accurately recording risk through the recent warm and wet weather period.

Growers can hover over the models ‘predicted temperatures plot’ to determine forecast temperatures. Where the mean day/night temperatures are 20 degrees or more, growers will notice the risk drops significantly.

It would be prudent to protect damaged canes on sites where Psa has remained a problem through late spring and early summer, and where innoculum load is likely higher - particularly if new growth is present or pruning rounds have been completed since copper was applied. Also, take care to avoid applying copper in high humidity or through the heat of the day, to minimise any risk of fruit marking or phytotoxicity.

Read more about how to make the most of the Psa Risk Model and how to easily log in here.