fumigated, not fumigated, or fumigated and infested with antagonists, 

 respectively. In greenhouse experiments the mean lesion length on 

 stems increased as the inoculum density was increased in fumigated soil; 

 lesion length, however, did not increase as the inoculum density was 

 increased in fumigated soil with antagonists added. In nonamended soils, 



the disease incidence and mean lesion length were ?0% and 2.22 cm, 



ir- 

 respectively, at the highest inoculum density, 5 X 10 chlamydo spores 



per pot. At that inoculum density in antagonist amended soils, the 



incidence of disease and mean lesion length were hk% and 0.96 cm, 



respectively. 



In field experiments, disease incidence increased as the inoculum 

 density of the pathogen was increased in soils that were fumigated "but 

 not amended with the antagonists; disease incidence, however, did not 

 increase as the inoculum density was increased in soils that were 

 fumigated and amended with the antagonists. At 5000 chlamydo spores of 

 the pathogen per plant, disease incidence at harvest was 7% in soils 

 amended with the antagonists and 37% in nonamended soils. The pathogen 

 population decreased from 600 to 200 propagules per gram of soil during 

 the growing season in the soils amended with the antagonists, but 

 increased from 1000 to over 5 X 10 propagules per gram of soil in non- 

 amended soils. 



Control of disease was attributed to the abilities of the antago- 

 nists to inhibit the saprophytic activities of the pathogen. The 

 population of the pathogen was stable or decreased in fumigated soil 

 that had been amended with the antagonists, but the pathogen population 

 increased 20-fold in nonamended soils. Microbial interactions which 



