48 

 Discussion 



The application of selected antagonists to soil reduced the inci- 

 dence of Fusarium crown rot of tomato under field conditions. Similar 

 results were obtained in experiments done under growth-chamber and 

 greenhouse conditions (Section I). 



In the past, antagonists usually have been selected for their 

 ability to inhibit a pathogen under pure culture conditions (2). For 

 several reasons these antagonists failed to reduce disease when applied 

 under field conditions. Of the eight reasons that Baker and Cook (2) 

 presented for such failures, the most important is probably the fact 

 that the environmental conditions in agar are unrelated to those in the 

 soil. The success of reducing Fusarium crown rot of tomato under growth- 

 chamber and greenhouse conditions was attributed to the formation of a 

 microbial community which inhibited the saprophytic proliferation of the 

 pathogen, rather than to the detrimental interaction of the pathogen 

 with any one species of antagonist (Section I, II). 



Yield was not affected by the different treatments because of the 

 atypically warm growing season. Fusarium crown rot of tomato is a cool 

 weather disease (l4) , Production operations in the area reported little 

 problem with the disease during the 1979-1980 growing season, when temp- 

 eratures rarely dropped below 10 G. 



The lower inoculum densities of the pathogen in amended soils early 

 in the season probably were responsible for the reduction of disease 

 severity. Rowe and Farley (27) reported that the severity of Fusarium 

 crown rot of tomato is dependent upon the early infection of the tomato 

 plant. The absence of an increase in the population of the pathogen in 



