The latest update to the online NZPPI Weather and Plant Disease Management Platform for myrtle rust is ground breaking and will enable more precise spraying.

HortPlus and Plant & Food Research have upgraded the Myrtle Rust Climate Model with new modelling that gives plant producers real-time spray management advice based on the actual sprays they use in their nursery.

HortPlus Director Mike Barley said the upgrade was pioneering as it was the first time specific advice on fungicide use had been included in the MetWatch platform for plant disease management.

“It will allow plant producers to be more accurate and efficient with the use of chemical sprays to combat myrtle rust this season. This is especially important as myrtle rust spreads down the country.”

Rather than spraying seedlings on a typical 14 day cycle, the Myrtle Rust Climate Model enables producers to time spray applications based on real time disease risk. This can significantly reduce the number of applications while improving disease control.    

“The earlier version didn’t allow for specific spray information so modelling was based on average spray responses combined with MetWatch weather data. The new update is based on the actual active ingredients being used at each nursery so the spray management advice is much more precise,” Mike said.

Plant & Food Research scientist Rob Beresford has been conducting trials on myrtle rust management based on the online tool. He said his trials have been invaluable in providing information on spray efficacy and the Myrtaceae species that are most or least susceptible to myrtle rust.

 “For example, we’ve discovered that mānuka is more resistant to myrtle rust so doesn’t need as much spraying as we previously thought.”

The customised tool is the result of a collaboration between New Zealand Plant Producers (NZPPI), HortPlus and Plant & Food Research to improve disease management outcomes for growers and for New Zealand as a whole.

 To access the update, growers go into the Disease/ Myrtle Rust Cumulative Risk section of the online tool, click on the new ‘Add Spray’ button then select the date and chemical sprays used in their nursery. The interactive tool will then indicate, in graph form, the next ideal spray timing (Action Threshold) based on the applied sprays and local weather conditions (temperature, humidity and rainfall). The spray timing will differ depending on the spray they have chosen.

Trials and further development of the platform will continue and over time may include other disease climate models, such as those affecting fruit and vegetable growers. The platform and myrtle rust model is free for NZPPI members and, thanks to Ministry for Primary Industries funding, is free for other users until December 2023.