WASTES IN RELATION TO AGRICULTURE AND FORESTRY 



13 



spread by mosquitoes that are often spawned un- 

 der irrigation agriculture. Needed research should 

 be supported to the fullest extent feasible. 



Plant Disease Agents 



Diseases of crops, ornamentals, and trees have 

 caused losses in billions of dollars. Many of these 

 diseases are transmitted via air, "water, or soil — 

 that is, by contamination of the environment. 



Black shank of tobacco has been a very serious 

 disease in several tobacco-growing areas. It is 

 spread by contaminated water, soil, or plants. The 

 disease spores can contaminate ponds or streams 

 into which infested fields drain. The disease per- 

 sists for many years in some soils but not in others. 

 Research on this problem has developed resistant 

 plant varieties and a system of field sanitation. 



Eed stele disease of strawberry is an example 

 of a plant disease fungus that persists in con- 

 taminated soil for many years even if strawberries 

 are not present. 



Stem rust of wheat is an example of a plant dis- 

 ease that is often spread, with disastrous results, 

 by contaminated air. This disease has cost agricul- 

 ture billions of dollars in losses. Countering the 

 broad transmission of strains of this disease by 

 tainted breezes has gained through development of 

 disease-resistant varieties of grains. Since the 

 disease organism mutates and attacks previously 

 resistant varieties, a continuous breeding program 

 is essential. In fact, one of the most laudable con- 

 tributions of research in the United States is that 

 of developing control measures for stem rust of 

 wheat — a disease that can ravage millions of acres 

 of a food crop by contaminated winds. 



White stringy root rot of conifers is a disease 

 caused by the fungus Fomes annosus Fr. It is pres- 

 ent throughout our softwood forests. Airborne 

 spores inoculate freshly cut stumps. Once tree roots 

 are infected, the fungus may survive below ground 

 for 50 years or more. 



Although the potato blight epidemic that caused 

 such widespread starvation and misery in Ireland 

 occurred over a hundred years ago, we still know 

 very little about the spread of such plant disease 

 epidemics by a contaminated environment. 



Research on the control of plant pathogens that 

 contaminate the soil needs particular attention, 

 since few are subject to cont rol by either chemicals 

 or plant breeding. High priority musl be given to 

 studies on changes in microbial populations in soils 



on incorporation of specific crop residues, with 

 especial emphasis on the extent to which popula- 

 tions of plant pathogens on the soil are suppressed. 



Plant disease agents carried by air, water, and 

 soil can be just as disastrous to man's welfare as an 

 infectious agent such as Salmonella typhosa — the 

 cause of typhoid fever. Research towards mini- 

 mizing the prevalence of these agents is tanta- 

 mount to improving environmental quality for 

 man's welfare. This is a high priority objective- 

 Allergens 



The Public Health Service reports that in the 

 average year, there are 12,646,000 sufferers from 

 asthma or hay fever, or both. Of these, about 5 

 million are asthma sufferers, and about 75 percent 

 of the asthma cases are due to pollen. The remain- 

 ing 7,646,000 suffer from pollen allergies. Costs in 

 terms of medical treatment and workdays lost are 

 enormous. 



There is very little research underway designed 

 specifically for the control of plant species that 

 produce allergenic pollen. In fact, there is no com- 

 plete catalog of allergenic pollen. 



Chemical control by herbicides having high 

 physiological specificity offers a real possibility 

 for the weeds that are troublesome. Pollen is car- 

 ried long distances by wind, and any control 

 measure must significantly reduce pollen counts. 



The evidence suggests that very rewarding re- 

 search could and should be undertaken in this a 

 of serious aerial contamination. 



Agricultural and Industrial Chemicals 



The use of synthetic organic chemicals has been 

 beneficial to man and his environment. But the dis- 

 charge of some of these chemicals into the environ- 

 ment has induced problems. These chemicals in- 

 clude such substances as household detergents and 

 the more recent insecticides, herbicide-. des, 



and nematocides. 



Detergents 



Agriculture and forestry have interest in prob- 

 lems caused by detergents. The excellence of these 

 chemicals as cleansing agents is related to their 

 high capability to disperse colloidal particles. 

 They also disperse -oil colloids. A dispersed soil 

 has relatively low hydraulic conductivity in either 

 the saturated or unsaturated state. An installation 

 such as a septic tank with its distributing field 



