188 DISEASES OF GLASSHOUSE PLANTS 
(5) Cucumbers, tomatoes, and other plants with 
heavy masses of foliage should be trimmed before— 
spraying to allow the fungicide to be applied thoroughly, 
but the spraying must follow immediately after com- 
pletion of the trimming to prevent infection from the © 
spores which have been distributed over the leaves by the 
disturbances of the foliage. 
Soil Fungicides 
While spraying the aerial portions of plants for 
purposes of disease control has long been in practice, 
but little attention has been given in the past to the 
treatment of diseased soils in which plants are growing. 
The general view has been that any compound capable 
of destroying the disease organism would injure the ~ 
plant at the same time. In consequence, any treatment 
directed towards the destruction of disease in the soil 
has been applied at a time when no plants were being 
grown. Recently, while investigating “ damping off” 
of the tomato, a soil drench was devised which, while 
causing no injury to the living plant, possesses fungicidal 
powers. This compound, which for convenience has 
been named “ Cheshunt Compound,” has already been 
described on page 61. The treatment was devised to 
control “‘ damping off,’ but has given satisfactory results 
against other fungal diseases originating in the soil. 
Dusting 
Of recent years the practice of dusting plants with 
dry powdered fungicides and insecticides has been 
introduced to replace spraying. The process, which is 
largely due to the initiative of Professor H. H. Whetzel, 
of Cornell University, is still in its infancy, but the 
excellent results obtained have earned for it considerable 
praise by both scientific and practical investigators. 
To be entirely satisfactory the dust should take the 
