NATURE AND MANAGEMENT OF BACTERIAL CANKER-SOUR SKIN BLACK MOLD, SMUT, LEAF BLIGHT, AND SEEDBORNE DISEASES OF ONION

摘要

Soil samples taken from fields cropped to onion and non-onion plants at various times during the growing season and assayed for population levels of Burkholderia cepacia, the cause of the bacterial canker-sour skin disease, indicated that the levels in soils cropped to onions varied from 20,000 to 200,000 colony forming units (CPU) of the bacterium per gram of air dried soil during June to October, Soils with a history of onion culture on which corn, green beans, and pumpkin were grown showed significant levels of B. cepacia (up to 39,900, 20,300, and 12,200 CFU/g soil, respectively. Other fields previously cropped to onion and then planted to radish repeatedly, radish and lettuce in succession, squash , soybean, and turfgrass had moderate or very low levels of B. cepacia resident in the soils. In turfgrass fields the levels ranged from 0 to 635 CFU/g of soil. For the squash, soybean, and radish alternated with lettuce fields, the levels were 647,825, and 909 CFU/g of soil, respectively. Radish fields sampled ranged from 647 to 8,230 CFU/g of soil.