Damping-off of sugar beet in Finland: III Effect of temperature and disease forecasting

The effect of temperature on the severity of damping-off of sugar beet was studied under controlled conditions. The disease incidence increased with increasing temperature. When the time up to emergence in a finesand soil was characterized by low temperatures (8°C night, 15°C day), a period of 14—21 days immediately after emergence caused a strong increase in disease incidence. In peat soil, even 7 days was enough to initiate such an increase. In neither of the soils used did three days of high post-emergence temperature cause any marked disease increase. When the pre-emergence period was characterized by high temperatures (15°C night, 25°C day) the disease was at a high level and in the very fine sand soil could not be lowered by lower temperatures. In the peat soil, however, a constant, low postemergence temperature significantly inhibited the development of the disease. The possibilities of damping-off forecasting by comparing the disease incidence in pot experiments to damping-off in the field seemed rather limited. When the temperature is taken into account, a negative prognosis may be possible. The basis of such a prognosis is the determination of the inoculum potential of the soil