22 August 1997

Blight forecast scores

BLIGHT forecasting systems under evaluation at Harper Adams College have given better disease control from fewer sprays for the third season running.

But visitors to an open day at the Shropshire college felt disease levels in the trial were unacceptable, diminishing the value of the work.

Study director, Peter Jenkinson, acknowledged that burning off maincrop haulm in August will hit yield. But the computer triggering of spraying achieved equivalent, or better, blight control using fewer applications, he stressed.

In previous years the British Potato Council-funded trial showed the systems could cut sprays and still give acceptable control. Treat-ments directed by a Hardi Metpole and Negfry computer model in 1995 saved five fluazinam (Shirlan) sprays, compared with treatments used by local farmers. Last year the system saved two sprays.

This year the system has again triggered fewer treatments, as has the first use of the Adcon/Ullrich-Schrodter system.

The trial is using Brodick, Maris Piper, Fianna and Russett Burbank. All varieties received six conventional sprayings, while Hardi/Negfry monitoring prompted three sprays on Maris Piper and Fianna – the other system demanded four. On Russett Burbank plots the first system triggered four spray and the other five. &#42