STORAGE OF SEED POTATOES IN PALLET BOXES .1. THE ROLE OF TUBER SURFACE MOISTURE ON THE POPULATION OF ERWINIA BACTERIA

Three stocks of seed potatoes contaminated with soft rot Erwinias were stored for 172 days in a commercial pallet box store. Three treatment s were applied: naturally ventilated boxes, forced air ventilated boxe s and single tubers on trays. Skin resistance values were 2.3, 9.4 and 19.3 megohm respectively. Rewetting events numbered 4, 7 and 15. Erwi nin carotovora a pv. carotovora (Ecc) and Erwinia carotovora pv. atros eptica (Eca) declined in all stocks and treatments. Ecc declined signi ficantly faster in the forced air ventilated treatment. The more frequ ent rewettings in the trays reverse the benefit of their drier skins. In the earliest sprouting stock, the naturally ventilated, but not the forced ventilated boxes, showed a decrease in skin resistance and cor responding increase in Ecc as spring approached. Forced ventilation in the first 14 days after harvest halved the level of silver scurf comp ared to the naturally ventilated treatment.