LONG-TERM EFFECT OF SOIL SOLARIZATION FOR THE CONTROL OF ROSELLINIA-NECATRIX IN APPLE

The effects of pre- and post-planting soil solarization on white root rot of apple caused by Rosellinia necatrix were examined in two naturally infested orchards. The pathogen was eradicated in solarized soil to a depth of 30 cm. Partial or complete destruction of the pathogen was obtained in solarized-shaded (partially shaded by the tree canopy) plots. No reinfestation of solarized and solarized-shaded soil was observed 2 years after treatment. No death of replanted apple trees occurred in the solarized plots up to 2 years after solarization, whereas 60% of trees died in untreated plots. No disease developed during the third year after solarization in an existing apple orchard, but a low rate of disease recurred in the fourth year. In contrast, mortality in diseased trees in the absence of solarization reached 100%, 4 years after treatment. Two previously solarized soils, out of seven tested, caused reduced growth of the pathogen, indicating induction of soil suppressiveness by solarization. © 1990.