Soil solarisation: a cultural practice to reduce viability of sclerotia ofSclerotinia sclerotiorum in New Zealand soils

Soil solarisation reduced the viability of sclerotia of Sclerotinia sclerot iorum which were buried in the soil at a depth of 10 cm in three field tria ls (Lincoln 1997, 1998; Blenheim 1998). Solarisation for 8 weeks (Lincoln a nd Blenheim 1998) had a greater effect than for 4 weeks (Lincoln 1997). Scl erotial viabilities in solarised plots were reduced to 52% (Lincoln 1997), 8% (Lincoln 1998), and 0% (Blenheim 1998) compared to 95, 53, and 89% for n on-solarised plots, respectively. Average maximum temperatures recorded for solarised plots over the trial periods ranged from 33 to 35 degrees C, tem peratures were c. 8-10 degrees C lower in non-solarised plots. The potentia l for using soil solarisation to re duce levels of S. sclerotiorum scleroti a in New Zealand horticultural soil is discussed.