From samples sent in for resistance testing by various chemical companies including Bayer New
Zealand over the past two seasons, it has been concluded that the strobilurin group are ineffective in
controlling Septoria leaf blotch in most parts of New Zealand. The DMI group, which includes
Prosaro® and Opus®, has been on the centre of attention as this group has been the primary control
method for Septoria leaf blotch in New Zealand over many seasons. The new SDHI group, which
includes Aviator® Xpro, has been shown to have a high sensitivity to Septoria leaf blotch.
Earlier this year Bayer New Zealand sent another batch of samples from the 2014/15 season taken
from a range of sites surveyed throughout New Zealand to the Resistance Testing Centre in
Monheim, Germany. The results suggest that Septoria leaf blotch is still highly resistant to the
strobilurin group as expected. The triazole group has a similar level of sensitivity and there is no
change in the baseline level of the SDHI actives treated (that is, there is no evidence of resistance).