METHODS OF CONTROL 197 



frame, or with diseased tomatoes, the 

 violets, and a number of other hosts grown 

 as alternating crops. It goes without say- 

 ing that the grower should not knowingly 

 bring in sick soil into the greenhouse, nor 

 should a sick soil from indoors be dumped 

 in the open where sweet peas or any other 

 crops are likely to be grown for ornamental 

 or commercial use. Care should be taken 

 to allow no access to diseased violets or 

 diseased plants of any kind. 



CONTROL OF OUTDOOR SICK SOILS 



Unlike greenhouse soils, affected areas 

 outdoors are not so easily treated. In a 

 small garden plot, as in the home garden 

 for instance, a sick soil may be sterilized 

 either with steam, using the inverted pan 

 method, or with formaldehyde, as in the 

 case of the greenhouse. Where sweet peas 

 are grown on a large scale, as for seed pur- 



