39 

 (Section l). The purpose of this study was to test the potential of 



antagonists to control Fusariura crown rot of tomato under field 



conditions. 



Materials and Methods 



The field used for the experiments during the 1979-1980 season was 

 located near Delray, Florida, and contained Pompano fine sand with a pH 

 of k.5 (measurement obtained from a 1:2 suspension of soil in 0.01 M 

 GaClo). The soil was fumigated with methyl bromide-chloropicrin 

 (67/33% v / v ) at 1 kg of fumigant to 20 m^ of soil injected approximately 

 20 cm below the soil surface via three chisels. Plastic mulch (0.25 mm 

 thick) was placed over the bed immediately after injection of the fumi- 

 gant. Each bed was 1 m wide and the beds were separated by 1-m access 

 rows that were not fumigated. Two weeks after fumigation, 5-wk-old 

 tomato ('Walter') transplants were planted 30 cm apart in two rows which 

 were 50 cm apart on each bed. Subsurface irrigation was maintained at 

 approximately 40 cm below the bed surface. Cultural practices were 

 similar to those employed in the area. 



Tomatoes had not been grown previously in the field, and the patho- 

 gen was not detected by soil dilution plating on a selective medium (l6) 

 before planting. This situation allowed the establishment of field plots 

 with defined initial inoculum densities of both the pathogen and the 

 antagonists. The pathogen was added to the soil by injecting 10 ml of a 

 suspension of chlamydo spores under the plastic mulch at opposite sides 

 of the transplant, 10 cm from the transplant hole. Macroconidia of the 

 pathogen were incubated at 28 G for k wk at 10° macroconidia per ml in 

 autoclaved deionized water to induce chlamydospore formation (Section I). 



