WASTES IX RELATION TO AGRICULTURE AND FORESTRY 



43 



Evaluations of the relative contribution of burn- 

 ing agricultural wastes to photochemical air pol- 

 lution have been attempted. The studies indicated 

 concentrations of photochemically active hydro- 

 carbons were negligible at a mile and a half from 

 the fire when more than 1,000 acres of -wastes were 

 burned. The emissions of hydrocarbons and oxides 

 of nitrogen from burning of agricultural wastes 

 were considerably less per ton of fuel consumed 

 than those in auto exhaust. The burning of fruit 

 tree primings, rice straw, barley straw, and dry 

 native range brush produced approximately 14, 9, 

 18, and 7 pounds, respectively, of hydrocarbons 

 compared with 130 pounds of the same hydrocar- 

 bons in auto exhaust per ton of fuel consumed. It 

 appears from limited study that the burning of 

 agricultural wastes does not add significantly to 

 the burden of pollutants in community air. The ef- 

 fects of smoke on visibility from burning the agri- 

 cultural wastes, however, may be a significant 

 esthetic factor. 



As agricultural land in the United States be- 

 comes more limited and agriculture becomes more 

 intensive, the danger of plant debris carrying dis- 

 eases and other pests to the succeeding crops 

 becomes greater. Control of the plant diseases, 

 preferably by disease resistance or nonchemical 

 means, could solve the problem. But until such con- 

 trol becomes a reality, destruction of the plant 

 debris by burning will be a common practice. 



A case in point here is the destruction of plant 

 residues of grass seed crops in western Oregon by 

 burning, which is the only practical control for the 

 blind seed disease, but which has led to an air pol- 

 lution problem. Alternative methods of control 

 must be found if the pollution problem is to be 

 abated while enabling the multimillion-dollar 

 grass seed industry to remain prosperous. 



Many plant diseases are transmitted through 

 plant residue, including late blight of potato, cot- 

 ton vertieillium wilt and bacterial blight, apple 

 scab, brown rot of stone fruits, and leaf spot of 

 tung. to name but a few. The extent of the plant 

 disease problem associated with plant residues is 

 not known for many crops. Some estimates have 

 been made, however. For example, observations in 

 Maine and other States indicate that culled piles of 

 potatoes outside potato storage houses, along rail- 

 way tracks, and on farms are primary sources of 

 infection for late blight, a disease that causes an 



estimated average 4-percent loss of the potato crop 

 each year. 



In the southeastern United States piles of litter 

 left in peanut fields are often an important source 

 of stable fly breeding. Similarly, in other areas of 

 the United States, rotting hay and straw provide 

 suitable breeding places for the stable fly and house 

 fly. Volunteer wheat, resulting from grain waste in 

 inefficient harvesting practices, provides a breed- 

 ing ground for the wheat curl mite, the vector of 

 wheat streak mosaic. Volunteer beets are a source 

 of beet yellow virus for reinfection of subsequent 

 beet crops in the western and northwestern United 

 States. Pink bollworms overwinter in waste cotton 

 bolls and cottonseed left in fields. The European 

 corn borer and sugarcane borer overwinter in the 

 stalks remaining in the fields. 



The European corn borer is one of the most de- 

 structive pests to sweetcorn in the United States. 

 It causes coarse, broken stalks, poor ear develop- 

 ment, and dropped ears, resulting in reduced yield 

 and increased cost of harvesting. The average an- 

 nual crop loss is estimated at 3.5 percent of the 

 total production. The sugarcane borer is the most 

 injurious insect attacking sugarcane in the United 

 States and is responsible for an annual estimated 

 loss of 12.1 percent. This insect also attacks corn, 

 rice, and sorghums. The pink bollworm constitutes 

 a threat to cotton comparable to the boll weevil. 

 The stable fly is a serious pest of domestic animals 

 and man throughout the United States, especially 

 in North Central, Eastern, and Southeastern 

 States. Reliable estimates from Illinois indicate 

 that heavy stable fly outbreaks can reduce milk 

 production by as much as 25 percent and reduce 

 beef gains materially. In the Hard Red Winter 

 wheat areas of Kansas and Nebraska, wheat streak 

 mosaic caused an estimated loss of 15 million 

 bushels in 1949 alone. The average annual loss from 

 this disease is estimated at 1 percent of the total 

 wheat production in the United States. The an- 

 nual loss of beets from yellows disease is estimated 

 at 6 percent : potato los>es from aphid-transmitted 

 virus diseases are estimated to be in excess of 3 per- 

 cent annually. 



Residues and Trash in Forests and Forestry 

 Operations 



Twenty-five million tons of logging debris are 

 left in woods during the average year. This ma- 

 terial is a tire hazard. Some of the most disastrous 



