March 23, 2020
Using an artificial inoculation protocol, the efficacy of eight fungicides* were applied as curative or protectant treatments against myrtle rust on two native New Zealand species – New Zealand ‘Magic Dragon’ (Lophomyrtus x ralphii) and pōhutukawa (Metrosideros excelsa).
The impact of rate (x2), frequency (single or double) and timing (pre- or post-inoculation) of fungicide application were investigated.
The results
- overall, the most effective fungicides tested across both species were those that included a demethylation inhibitor and strobilurin mix, notably tebuconazole and trifloxystrobin (Scorpio®) and cyproconazole and azoxystrobin (Amistar Xtra®)
- these fungicides significantly reduced infection of host plants relative to the water control
- timing of application significantly affected bioefficacy, with applications made 7 days before inoculation or 7 days after inoculation being generally the most effective
- the rate of fungicide application was not significant for both host species with few interaction terms showing overall significance
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*Fungicides trialled:
- tebuconazole/trifloxystrobin
- cyproconazole/azoxystrobin
- fosetyl aluminium
- triforine
- triadimenol
- oxycarboxin
- copper
- tebuconazole
March 2020