47 6 



Yearboo\ of Agriculture 1949 



miles an hour or when there is enough 

 turbulence to make the air bumpy. 



ARE FISH AND WILDLIFE harmed by 

 insecticides? The use of DDT at the 

 rate of a pound or less an acre has pro- 

 duced no serious effects on birds or 

 mammals. This dosage can, under cer- 

 tain conditions, cause considerable in- 

 jury to aquatic life. Game fish are little 

 affected by 1 pound per acre applica- 

 tions, but the forms providing the bulk 

 of fish food are sometimes sharply de- 

 pleted. High dosages, on the other 

 hand, can be very injurious. Therefore, 

 with DDT or other new insecticides, 

 the application rate should be held to 

 the minimum necessary for effective 

 control of the insect and, where ex- 

 tensive areas are to be treated, the 

 work should be done under expert 

 guidance. 



THE COST of applying DDT sprays 

 to forests has ranged from $1 to $3 

 or more an acre, depending on the 

 type of terrain, size of the area to be 

 treated, distance from the landing strip, 

 dosage rate, and other conditions. 



Such expenditures are not excessive 

 for the protection of most forest areas 

 when one takes into account the actual 

 value of merchantable timber, the 

 added fire-protection costs that may 

 result from standing dead timber fol- 

 lowing an insect epidemic, the effect 

 of loss of timber on the economy of 

 the community, and the indirect losses 

 such as erosion of watersheds. 



Undoubtedly costs will decline as 

 improvements are made in equipment, 

 spray mixtures, and application pro- 

 cedures, with the result that more use 

 will be made of aircraft for combating 

 forest insects in the future. 



It seems probable that those im- 

 provements will make it possible to 

 locate outbreaks while they are in their 

 initial stages and to apply insecticides 

 before the infestations spread over 

 large areas. Future trends are expected 

 to be toward development of more 

 sensitive photographic methods for 

 early detection of insect damage, the 



use of larger aircraft for greater range 

 of operation, the development of more 

 efficient spray equipment designed on 

 aerodynamic principles, and the appli- 

 cation of various new insecticides. 



J. S. YUILL attended the University 

 of Arizona and the University of Cali- 

 fornia. He has been employed as an 

 entomologist in the Division of Forest 

 Insect Investigations, Bureau of Ento- 

 mology and Plant Quarantine, since 

 1935. Until 1942 he was stationed at 

 Berkeley, Calif., where he carried on 

 research on various forest-insect prob- 

 lems of the California region. During 

 the Second World War he served as 

 a malaria control officer in the Navy. 

 Since the war he has been engaged in 

 the development of aerial spraying for 

 control of forest insects at the Agricul- 

 tural Research Center, Beltsville, Md. 



G. B. EATON, a native of Massachu- 

 setts, is an entomologist in the Division 

 of Forest Insect Investigations, Bureau 

 of Entomology and Plant Quarantine. 

 He was graduated from Syracuse Uni- 

 versity in 1934, and has been in forest- 

 insect research at various field stations 

 since that time, except for 3 l /% years 

 as entomologist in the Army Sanitary 

 Corps. Since 1946 he has been at the 

 Agricultural Research Center, working 

 on the development of aerial spraying 

 for forest-insect control. 



