Populations of total green fluorescent bacteria and total pectolytic bacteria on lower healthy leaves from 7- to 8-week-old lettuce plants grown on nonridged organic soil reached 4.9 × 10⁴ and 2.7 × 10³ cells/cm² of leaf tissue, respectively.  The corresponding populations on senescing leaves were 1.3 × 10⁴ and 3.8 × 10³ cells/cm² of leaf tissue.  On lettuce grown on ridges the populations of all bacteria were 10- to 100-fold less.  After a rain, counts of total pectolytic bacteria on healthy leaves taken from 3- to 5-week-old plants reached 6.1 × 10⁴ cells/cm² of leaf surface.  Populations on older healthy leaves and senescing leaves were not altered by rain. In soil from under mature nonridged lettuce, the populations of total green fluorescent and total pectolytic bacteria reached 5.3 × 10⁴ and 2.9 × 10⁵ cells/g of oven dry soil, respectively.  the corresponding populations in ridged soil were 1.1 × 10⁴ and 8.3 × 10⁵ cells/g of oven dry soil.  Usually less than 50% of the pectolytic bacteria isolated from healthy and senescing leaves produced soft rot symptoms within 48 hours on wounded detached lettuce leaves.  On healthy and senescing leaves from ridged and nonridged lettuce, the populations of pathogenic green fluorescent bacteria were variable and usually less than 4 × 10² cells/cm² of leaf surface.  In soil from under ridged and nonridged lettuce the populations of pathogenic pectolytic bacteria were either undetectable or less than 3.1 × 10⁴ cells/g of oven dry soil.  Populations of pathogenic green fluorescent bacteria were either undetectable or less than 4.0 × 10³ cells/g of oven dry soil.

Additional key words: pectolytic bacteria, green fluorescent pseudomonads, soft rot bacteria.