254 The Philippine Journal of Science ims 



fungus that will not attack other plants, this fungus can be 

 largely kept out of the soil by a system of starvation brought 

 about by crop rotation. As a rule, the majority of the fungi can 

 only live in the soil without their host plant for from one to three 

 years. There are exceptions to this rule, but generally speaking 

 a systematic, two- or three-year, crop rotation will reduce the 

 fungus pests of a specific crop to a minimum and in this way 

 keep the disease at a point where little injury is done. The 

 first consideration from a control viewpoint, therefore, is sanita- 

 tion, which includes the destruction of diseased plants and fungi 

 by burning, and the second is a systematic system of crop 

 rotation. 



CULTURAL METHODS 



Another very important consideration is that concerned with 

 the culture of the various crops. By culture methods is meant 

 the proper preparation of the soil, the proper method of planting, 

 the proper distance between plants, the proper amount of shade, 

 the proper soil and locations adapted to crops, and the proper 

 methods of cultivation, pruning, and other practices that will 

 produce a healthy and vigorous plant and one that will give 

 the greatest yield. A healthy, vigorous plant will, to a marked 

 degree, withstand disease; therefore any practice that will 

 produce such a plant will, in the majority of cases, reduce 

 the prevalence and severity of the disease. In the Philip- 

 pines, on the whole, very poor culture methods are practiced. 

 A large number of cases may be cited, but as examples 

 the culture of coconuts, abaca, cacao, and citrus are suffi- 

 cient. These plants are usually planted entirely too thick. 

 This thick planting produces humid conditions and a lack 

 of aeration, both of which are highly favorable to disease pro- 

 duction. Once a disease becomes established in a thickly planted 

 area, it spreads rapidly from plant to plant. These conditions 

 are true in regard to coconut bud rot, abaca heart rot, and the 

 black rot of cacao. New plantings should be made according 

 to the best-accepted and approved methods of planting. It is 

 usually true that those conditions that will induce a crop to 

 produce at a maximum will also provide conditions that are 

 unfavorable for the production of disease. In proper culture 

 methods trash, consisting of dead portions of plants and other 

 ; refuse, should never be allowed to accumulate under the plants, 

 for this material aifords a favorable place for the hibernation 

 and sometimes the development of many fungi causing plant 

 diseases. Clean culture methods will necessarily reduce the 



