256 The Philippine Journal of Science isis 



should be thoroughly heated for from thirty minutes to one 

 hour, taking care that the humus is not removed by burning. 

 It is not necessary to burn the soil, but a temperature from 60° C. 

 to 100° C, that is, just high enough so that a person cannot pick 

 up the soil in his hands is sufficient. The sterilized soil should 

 then be shoveled into seed flats that have been thoroughly dried 

 by placing them in the sun or better still those that have been dis- 

 infected with a 2 per cent formalin solution. The soil is ready 

 for planting as soon as it cools. 



FORMALIN DISINFECTION 



Formalin may be used for soil disinfection, but it is not to 

 be preferred to heating, since the soil cannot be used for planting 

 for at least one week after the application. The soil to be dis- 

 infected should be thoroughly prepared and placed in seed flats. 

 It is then drenched with a formalin solution composed of 1 

 part of commercial formalin (40 per cent formaldehyde) to 150 

 to 200 parts of water. The flats should be covered with cloth 

 or banana leaves for one to two days to retain the fumes. The 

 soil is then aired for one week before sowing the seed. 



FUNGICIDES 



Certain diseases may be economically controlled by the applica- 

 tion of fungicides. It must be remembered that in the majority 

 of cases the fungicides are applied as a preventive. They 

 protect the plant against infection. Once a fungus has gained 

 entrance to a plant tissue, the application of a fungicide will 

 be of no avail. In the control of superficial-growing fungi such 

 as the powdery mildews and sooty molds the fungicide will kill 

 the fungus directly. Spraying must be thoroughly done, so that 

 every part of the plant surface is covered with a film of the 

 preparation. This can be done only by the use of a proper 

 spraying apparatus that will produce a fine mist and thereby 

 cover the plant without drenching. The standard Bordeaux 

 mixture is the best universal spray for the Philippine Islands. 

 For special purposes other sprays may be used. 



The cost of spraying cacao trees for the black rot of pods, 

 based on the materials and cost of labor at 10 centavos per 

 hour, is 2 centavos per tree for each application. With ten 

 applications a year the cost would be 20 centavos per tree, 

 or the value of four cacao fruits. CoflFee spraying against rust 

 can be satisfactorily done for 20 centavos per tree for the year's 

 spraying. 



