INSECTS AND FOREST MANAGEMENT — CRAIGHEAD 375 



000,000 additional has been spent. This is obviously out of all propor- 

 tion to the immediate damage in the infested area, notwithstanding 

 the fact that in the early days of the gypsy moth, before it had been 

 acclimated to behavior more or less like that of a native insect, it 

 did cause tremendous destruction of oaks and associated pines in 

 eastern Massachusetts. It was the danger that it might spread south 

 and west throughout the eastern hardwood regions that warranted 

 large-scale, continued effort. 



Aside from the value of local suppression and prevention of spread 

 of the gypsy moth, this program developed many features of inesti- 

 mable value in the control of forest, shade, and fruit-tree insects. 



Spraying of woodland areas has developed into something of a 

 "big business" with a scientific background. Modern high-pressure 

 spraying machines and other equipment have been evolved to meet 

 the necessity. This technique now has wide application in all parts 

 of the country. The adaptability of the autogiro (pi. 10, fig. 1) for 

 applying arsenicals over forested areas has been demonstrated, and 

 this type of equipment bids fair in time to supplant completely the 

 use of ground machinery. It may lower the cost of the application of 

 insecticides to such a figure that it will be economical to protect forest 

 lands on the basis of the value of the threatened stand rather than 

 on the additional threat of spread to, and destruction of, forest in 

 other areas. Lead arsenate, one of the most widely used arsenicals, 

 was developed commercially. 



For many years an extensive program of parasite introduction was 

 carried on in an effort to establish the principal insect enemies of the 

 gypsy moth in this country. Most of the important foreign parasites 

 are now firmly established here and several of them have spread 

 throughout the gypsy moth infested region. This was the first large- 

 scale undertaking of this kind, and the knowledge gained has served 

 as a basis for studying parasites of a large number of injurious 

 insects. 



Many other destructive outbreaks of defoliators have occurred from 

 time to time in our forests but most of these developed unobserved 

 to such magnitude and declined with such abruptness that it has 

 been impossible to organize a control campaign. Suppression work 

 on many smaller direct-control projects in scenic and recreational 

 areas in our national parks and national forests have been carried out 

 during this period and will undoubtedly be conducted more frequently 

 in the future as the use of these recreational areas increases and costs 

 of application are reduced. 



CONTROL OF VEC5T0RS OF THE DUTCH ELM DISEASE 



The Dutch elm disease can logically be referred to here inasmuch 

 as its spread is entirely due to insect vectors, chiefly the small bark 



