tack had stimulated 20 years of agitation for 

 an eradication program. However, although 

 good control methods were available, they were 

 not considered sufliciently effective to justify 

 an eradication effort until the development of 

 a revolutionary approach to insect control. 

 This concept envisioned the elimination of an 

 insect pest by overwhelming the native popu- 

 lation with sterile male flies. Since female 

 screwworm flies when mated with sterile male 

 flies laid only infertile eggs, race suicide seemed 

 possible. 



Research entomologists of the Agricultural 

 Research Service conceived and developed the 

 sterile-fly method of insect control. Basic tech- 

 niques for the rearing, sterilization, and dis- 

 tribution of screwworm flies were perfected 

 and field trials demonstrated that screwworms 

 could be eliminated from localized areas. 



Early in 1957, a team of a veterinarian and 

 an entomologist surveyed the screwworm situa- 

 tion in the Southeast. Their purpose was (1) 

 to determine losses due to screwworms, (2) to 

 evaluate the probability of success of an eradi- 

 cation program using the sterile-fly technique, 

 and (3) to estimate the cost and duration of 

 such a program. The survey revealed an an- 

 nual loss of approximately $20 million in the 

 Southeast, half of which was in Florida. The 

 surveyors concluded that screwworms prob- 

 ably could be eradicated in 2 years at a cost 

 of about $10 million. 



Further investigation revealed that an area 

 of some 50,000 square miles, mostly in penin- 

 sular Florida, would require weekly dispersals 

 of .sterile male flies averaging 500 per square 

 mile. This called for a building of sufficient 

 size, and with adequate equipment, to produce 

 a minimum of 50 million flies per week. Ex- 

 pansion from an experimental fly-rearing 

 plant, with production of about 2 million flies 

 per week, required the design and construction 

 of new equipment, improvement and mechani- 

 zation of all operations synchronized to the life 

 cycle of the fly, a method of automatically pack- 

 aging irradiated pupae, and development of an 

 apparatus for airplane dispersal of packaged 

 flies. 



gram became available during the summer of 

 1957. Plans were immediately made to con- 

 vert an airplane hangar at Sebring, Fla., into 

 a huge fly-rearing establishment. Because of 

 the time required to remodel the hangar and to 

 design and build suitable equipment, operation 

 was not expected before July 1, 1958. In the 

 interim, it was decided to use the small, experi- 

 mental fly-rearing facility near Orlando, Fla., 

 to train personnel, and to test and develop new 

 methods and materials. 



The winter of 1957-58 was one of the coldest 

 and wettest in Florida histox'y. Low tempera- 

 tures in the north and excessive moisture in the 

 south decimated the screwworm population, 

 and restricted the pest to a comparatively small 

 part of southern Florida. In an attempt to 

 halt the northward movement of flies until the 

 new fly-rearing establishment could come into 

 operation, an artificial barrier was established 

 by dropping sterile male flies over the northern 

 part of the State. 



Production at the small plant was soon in- 

 creased to approximately 10 million flies per 

 week — a sufficient number to maintain an effec- 

 tive barrier and prevent widespread northward 

 migration of native flies. By late spring a 

 State quarantine line had been established 

 across peninsular Florida, extending east and 

 west from Ocala, to prevent the northward 

 movement of infested livestock. Animals in 

 transit from south of the quarantine line were 

 inspected and sprayed before they moved into 

 uninfested northern areas. 



iSL^SfeS'^Ei^ 



Eradication in operation 



Federal-State funds for an eradication pro- 



Mechanized fly-reai-ing facility converted from airplane 

 hangar, Sebring, Fla. 



16 



