WASTES IX RELATION TO AGRICULTURE AND FORESTRY 



29 



em Shore (Delmarva) broiler producers are pay- 

 ing about $9 per 1,000 birds ($0.09 per bird) to 

 contract removal companies for each cleaning, 

 which may be as frequent as four times a year. 



These studies emphasize that in earlier times 

 manure was highly prized as a source of soil fertil- 

 ity, whereas now it has become a costly burden to 

 many livestock operators. Furthermore, costs in 

 the future probably will rise as better pollution 

 abatement procedures become mandatory. These 

 procedures will not increase either the quality of 

 the product produced or the efficiency of produc- 

 tion. The economic value of manure as a fertilizer 

 or a gas does not compensate for the processing 

 required to modify the manure. Hence, manure 

 disposal systems can only add to the cost of pro- 

 duction. 



The adverse effects of accumulations of putres- 

 cible wastes on agriculture and forestry are grow- 

 ing to major proportions. Surface waters asso- 

 ciated with the farm, the ranch, or the forest are 

 a great source of potential revenue for fishing and 

 recreation if they can be kept free of oxygen-de- 

 manding wastes. On the other hand, the financial 

 burden to farmers for coping with wastes that are 

 offensive is becoming tremendous. 



Infectious Agents and Allergens 



Man's hard march down through the ages is 

 largely a record of calamities induced by three 

 grave adversities : Famine, pestilence, and war. 

 One can argue that the ravages of pestilence kept 

 famine from being more extensive than that re- 

 corded. However, an infectious agent attacking a 

 food crop caused one of the most serious famines 

 in history. Late blight of potatoes almost totally 

 destroyed this main food crop in Ireland in the 

 middle 1840's. Records indicate that the physical 

 misery and spiritual anguish because of the famine 

 caused by this one crop disease go far beyond any- 

 thing that ordinary experience equips one to 

 understand. The farmers suffered along with 

 everyone else. 



Phytopathogens 



The infectious agents of bacterial and fungus 

 diseases of field crops, fruits, and forest trees are 

 almost entirely carried by wind, water, or soil. 

 Many of the most serious virus diseases of plants 

 are carried by insects, and such insects cannot be 



ignored in evaluating the effects of infectious 

 agents on environmental quality. The destructive- 

 ness of these plant diseases merits a few illustra- 

 tions. 



In the 50 years or so since chestnut blight was 

 first discovered in this country, this disease has 

 killed virtually all of the American chestnuts, one 

 of our finest hardwoods, in its native range. 



Fifty years ago, white pine blister rust was mak- 

 ing extensive ravages in one of our finest conifers. 

 Our white pines would have been doomed within 

 a few years except that the fungus had to be trans- 

 mitted back and forth under proper aerial environ- 

 ment with the alternate hosts, currants and goose- 

 berries. An extensive campaign of eliminating 

 these alternate hosts saved our white pines. 



A wheat stem rust epidemic destroyed almost 

 300 million bushels of wheat in the United States 

 and Canada in 1916. 



In the epidemic year of 1935, stem rust caused a 

 60-percent loss to the wheat crop in Minnesota and 

 some of the neighboring States, and the loss for the 

 whole country was almost a quarter of the crop. 



As recently as the 1950 , s, losses to the Nation's 

 wheat crops from the highly destructive stem rust 

 race, 15B, were estimated at over 8.5 million 

 bushels annually in 1953 and 1954. A large part of 

 the spring wheat crop was virtually eliminated in 

 those years. 



In 1946, airborne spores of the late blight dis- 

 ease of tomatoes caused an estimated reduction of 

 50 percent of the national tomato crop. 



Thirty to forty years ago, Granville wilt of to- 

 bacco was taking 20 to 50 percent of that crop in 

 Granville County, N.C. The physical and mental 

 sufferings of the farmers because of economic 

 losses incurred by this bacterial disease were 

 enormous. 



Crop diseases may be spread by agricultural 

 machines that move contaminated soil on wheels 

 or carry disease organisms on the blades of 

 mowers. Thus, diseases are spread most rapidly in 

 the direction of cultivation. Contact of plants 

 often is necessary in the spread of disease fungi 

 which produce no spores but spread by slow my- 

 celial growth from one plant to the next. Texas 

 root rot and Rhizoetonia root rot exemplify such 

 cases. 



In picking beans when the ^ hies are wet. the 

 hands distribute the bacteria of bean blight so 



