Powdery mildew alert

17 August 2001

Powdery mildew alert

AS powdery mildew starts to infect sugar beet, Brooms Barn advises spraying crops, even those destined for early lifting, with full rate (0.625litres/ha) of Punch C (carbendazim + flusilazole).

That contrasts with advice from elsewhere indicating that sulphur, which costs about half as much, is more appropriate for beet for early harvest, admits Mike May.

"Its fairly clear to us that where the target is mildew you should use Punch C, full stop." He questions the statistical significance of other trials.

In IACR work, the treatment boosted output from late-September liftings last year by 9.4t/ha adjusted. "The yield increase is more than enough to pay for it," says Mr May.

If rust is severe or on irrigated crops or susceptible varieties, such as Duke, Swift, Rebecca and Rosanna, growers should consider switching to full rate Alto (cyproconazole), he says.

Sulphur can be added, at 10kg/ha, to increase mildew control. &#42

But again, contrary to advice from other sources, Brooms Barn does not advocate reducing rates in mixtures. "Despite the cost saving, the effectiveness and persistence of the chemicals is reduced accordingly."

ADAS recommends checking crops for both diseases at least once a week and treating early.

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