WASTES IN RELATION TO AGRICULTURE AND FORESTRY 



105 



of honey bees is important from the standpoint of 

 economics as well as the viewpoint of the apiarist. 



Broad-spectrum insecticides, such as DDT, mal- 

 athion, or carbaryl, will each control many kinds 

 of destructive insects. Research to develop controls 

 that are insect specific will be expensive, and 

 their use will increase the cost of control proce- 

 dures as well as reduce potential environmental 

 contamination. 



In view of the progress that has already been 

 made, prospects look good for developing com- 

 pletely selective methods of controlling practically 

 all of the major insect pests. The techniques in- 

 clude biological agents, specific insect attractants, 

 insect-resistant crop varieties, self-destruction 

 mechanisms such as sterile males, and chemical 

 insecticides that act on selective physiological 

 systems peculiar to the target insect. 



The existing coordinated research program 

 needs to be continued to develop better informa- 

 tion on insect population trends, insecticides with 

 higher biodegradability and lower persistence, 

 better knowledge of the chemical behavior of in- 

 secticides in soil and water systems, better predic- 

 tive techniques for forestalling insect invasion*, 

 better methods of insecticide application to mini- 

 mize drift and to reduce rates, and physical at- 

 tractants to aid in nonchemical control. 



Fungicides 



During the 1950*s, estimates of losses in produc- 

 tion potential owing to diseases of pasture and 

 range plants varied from 3 to 9 percent. Compar- 

 able figures for fruit and nut crops, and for vege- 

 tables are 2 to 38 percent and 2 to 23 percent, 

 respectively. Many of these diseases are controlled 

 by fungicides or bactericides. In some instances 

 residues of the chemical are present on the crop. 

 Although pollution from fungicides does not 

 appear to be significant, trace amounts of tetra- 

 chloro nitrobenzene (TCXB) and dithiocarbamate 

 fungicides have been detected in total diet .-tudies 

 conducted by the Food and Drug Administration. 

 One of the best nonchemical means of disease con- 

 trol is breeding for resistance, as is evidenced by 

 the large number of disease-resistant crop plants 

 under production. The result of additional re- 

 search in this area would be certain to result not 

 only in reduced clanger of pesticide pollution, but 

 in substantial savings to the producer and ulti- 

 mately to the consuming public. 



Nemaiocides 



Nematocides are widely used for control of 

 nematode pests of crops, particularly crops of a 

 high per acre value. The leading nematocides do 

 produce residues that may be a potential hazard 

 on more and more agricultural land. It is therefore 

 essential to develop other methods of nematode 

 control. 



As with insects, breeding for resistance to nema- 

 todes can go far toward eliminating present and 

 potential residues from use of nematocides. Here 

 again it is the most economical form of nematode 

 control. Xematode-resistant varieties of important 

 field and truck crops have been developed, includ- 

 ing stem nematode-resistant alfalfa, and nema- 

 tode-resistant soybeans and sugar beets. Addi- 

 tional research is needed on breeding and develop- 

 ment of methods of breeding for nematode 

 resistance in all crops and in ornamentals. Addi- 

 tional research to assess the impact of nematodes, 

 particularly on certain crops, also is needed to 

 properly assess the magnitude of the problem. 



Herbicides 



Use of herbicides has increased rapidly over the 

 past two decades because of their effective counter- 

 action to the waste in resources and effort caused 

 by weeds and brush. "Weeds cause waste in pro- 

 ductivity and efficiency of land use, losses in 

 product quality, and reduced efficiency of water 

 management. Weeds and brush can impair the 

 health and efficiency of people and of livestock. 

 They harbor insects and disease organisms that 

 attack crops. Weeds and brush in water sour 

 and on ditch banks, highway, railroad, and utility 

 rights-of-way. in fence rows, and on other areas 

 serve as reservoirs I'm- invasion of fields through 

 movement of seeds and vegetative parts by wind, 

 water, soils, and man and animal*. 



Weeds waste water, fertilizer, light, space, 

 equipment, and labor. The waste and losses caused 

 by weeds in crop- ranged from 2 to 20 percent of 

 the crop value for the period 1951-60. Far: 

 spend about £21 •_. billion annually to control weeds. 

 Yet, during the period 1951-60, the estimated an- 

 nual loss owing to reduced crop yields and quality 

 caused by weeds ranged from 3 to 25 percent, 

 pending on the crop. 



The economic and social significance of efforts 

 to reduce the Losses and waste caused by weeds can 



