13 November 1998

Strobs just cant be snubbed

CEREAL growers cannot afford to ignore strobilurin fungicides or use them too sparingly, according to ADAS pathologist Bill Clark.

Even at £70/t for wheat, most fungicides remain very cost-effective. But growers adopting a knee-jerk reaction to low prices and relying on cheaper triazoles will lose out on the significant yield enhancement of strobilurins, Mr Clark explained. "You wont fully optimise yields, and youll be stuck with those of 10 years ago."

As a taster of the value of the new products, Mr Clark said HGCA work suggests spending an extra £35/ha (£14/acre) on Amistar (azoxystrobin) instead of Opus (epoxiconazole) can boost wheat output by nearly 2t/ha (0.8t/acre).

Even on unresponsive varieties like Spark with very little disease, where Opus lifted output by 0.5t/ha (0.2t/acre), Landmark (kresoxim-methyl + epoxiconazole) and Amistar raised yields by almost twice and three times as much, respectively.

Mr Clark believes a key reason for the strobilurins advantage is that they keep crops greener for longer. "Wheat can put on 0.2t/ha a day during grain filling. So prolonging that period can be very significant."

Dose cutting, though, can be false economy. In single flag leaf spray trials, the economic optimum for Amistar in a programme with Opus as disease eradicant, was 0.6-0.7litres/ha. For Landmark the figure was about 0.9litres/ha though the response started to plateau at 0.6, he noted.