Fig. 4. Cabbage plants grown in clubroot-infested soils. Left: No treatment. 

 Right: Soil treated with hydrated lime and mercurous chloride. 



Photos by Robert L. Coffin. 



Effective Killer Sought 



Many soil fungicides and chem- 

 icals will kill disease organisms. The 

 problem is to find some that are 

 not costly to apply and, most im- 

 portant of all, not injurious to the 

 plant. In its search for a solution 

 to this problem, the Station has 

 conducted experiments to determine 

 the effectiveness of applying fertil- 

 izers containing soil fungicides to 

 combat clubroot and other diseases. 



More Control with Lime 



and Mercurous Chloride 



Several soils were collected, and 

 their pH values, water-holding cap- 

 acities, and other measurable char- 

 acteristics were determined. These 

 test soils were inoculated with a 

 small quantity of a soil known to be 

 infested with clubroot fungus. Some 

 form of Hme was worked into the 



soil at various rates of application. 

 Mercurous chloride or other fungi- 

 cide was then mixed with a com- 

 mercial fertilizer, usually a 5:8:7 

 fertilizer. Untreated soil received 

 fertilizer alone at the same rate of 

 application as the test soils. Seeds 

 were sowed at intervals after soils 

 were treated. At several intervals 

 after seeding, the plants were in- 

 spected for presence of clubroot and 

 for growth. 



It was interesting to note that the 

 less acid soils (soils with a high pH 

 value) had the least clubroot. None 

 of the organic fungicides gave as 

 good control of clubroot as the 

 combination of lime and mercurous 

 chloride. In several soils, this 

 combination completely controlled 

 clubroot. Many new fungicides 

 still remain to be tested before 

 definite conclusions can be drawn 

 regarding control cf this cabbage 

 pest. 



