Spray guidelines beat resistance

LEVELS OF powdery mildew spores resistant to the fungicide quinoxyfen remain low and stable, survey results show.

But growers must follow guidelines to ensure effective control and to keep levels low, said Dow AgroSciences‘ John Sellars.

“We have actively promoted guidelines to protect the efficacy of quinoxyfen against the threat of resistance. And the latest data suggests that it is working.”

The first mildew spores insensitive to quinoxyfen were detected in UK winter wheat in 2002, with further results in 2003 showing levels remained low, the company claims.

While the incidence of ‘insensitive‘ spores indicates the presence of resistance, there have been no field failures attributable to insensitivity, according to Dow AgroSciences.

The company recommends three key actions for effective mildew control:

  • Use quinoxyfen in combination with fungicides with different modes of action

  • Limit applications to a maximum of two per season, keeping rates between 50-100g ai/ha.

  • Only apply in the spring, do not use in the autumn

“In short, our advice for 2005 is to continue following our guidelines to gain and retain full benefit of quinoxyfen in controlling powdery mildew,” Mr Sellars concluded.