LEAF SCAR INOCULATIONS OF PEAR TREES WITH ERWINIA AMYLOVORA
We have inoculated leaf scars of pear trees with Erwinia amylovora, in an orchard of the Dax area, for two successive years. According to the year, and probably to the climatic conditions at leaf fall we have observed two kinds of results : (1) no symptoms were visible after inoculation in 1981 or, (2) few leaf scars inoculated in 1982 give rise to symptoms. The evolution of these symptoms took place in late autumn or winter before next growing season. In both cases the bacterial population vanished before spring in symptomless inoculated leaf scars. We never observed sudden development of symptoms in spring from these inoculated leaf scars.