27 November 1998

Tailored fungicides may pay their way

ADJUSTING fungicide dose according to variations in disease levels across the field is being investigated in a joint Danish project. Higher yields from better disease control and possibly lower fungicides usage are anticipated.

Initial work by the Danish Institute of Agricultural Sciences and Hardi International used a Hardi spray controller linked to GPS equipment to vary spray rate according to an application map. The system has been tested on six farms including one in the UK.

The main headache has proven to be mapping disease infection. So far this has been done mainly for mildew and Septoria using:

&#8226 Visual assessment when field walking;

&#8226 Previous years GPS yield mapping, on the assumption that crops are denser in higher yield areas and denser growth means more disease;

&#8226 Soil maps, on the basis that the better soils produce lusher, more disease-prone crops.

Considerable variations in disease severity were noted when field walking, says DIASs Karsten Bjerre. "The greatest amount of mildew occurred close to shelterbelts, hedges and trees. The pattern seemed relatively stable with a tendency for infection to spread into the field."

The work is ongoing.