104 BULLETIN 536, U. S. DEPARTMENT OF AGRICULTURE. 



and brittle that to remove the fruits before they ripen would be im- 

 possible. To this example might be added many others in which the 

 removal of ripening fruit would be equally impracticable. 



That the campaign was successful in eliminating the bulk of the 

 fruit ripening in Honolulu during the greater part of the year is evi- 

 denced by the inability of the Hawaiian Board to obtain any large 

 amount for their experimental work with parasites during the period 

 the campaign was in progress. Excepting May, June, and early 

 July, it was not an impossibility to gather the bulk of fruits ripening 

 hi Honolulu, but during these three months tons of ripening mangoes, 

 falling continuously, presented a situation that could not be success- 

 fully combated. (See Pis. XII and XIII.) While tons of mangoes 

 were carried daily to the incinerator or the city dumps, except from 

 the standpoint of city sanitation nothing of value was accomplished. 



Notwithstanding the fact that the bulk of the ripening and infested 

 fruits were collected and fruit-fly conditions were unquestionably im- 

 proved from the standpoint of the numerical abundance of adult flies, 

 the important fact remains that the number of fruit flies that suc- 

 ceeded in reaching maturity was sufficiently large to infest practi- 

 cally every fruit ripening within the city. Kerosene traps placed 

 throughout one of the cleanest sections of the city captured large 

 numbers of flies as proved by recorded data on file both with the 

 Hawaiian Board and this bureau. (See Table XXI, p. 76.) 



So far as the writers know, there is no way in which clean culture 

 can be made effective in Hawaii under present conditions. There 

 are no impelling incentives. The islands are thoroughly overrun 

 with the fruit fly, and this applies quite as much to the guava scrubs 

 in pastures (PI. II), on lava flows, and in mountain valleys and ra- 

 vines as within the city limits. By far the larger proportion of host 

 trees and shrubs are grown more for protection from the semitropic 

 heat and for their ornamental value than for their fruits (PI. VI). 

 Large numbers of the host fruits are not edible. The destruction of 

 host vegetation is out of the question until it can be proved that some 

 advantage worth while can be gained. To cut down all host trees 

 of Honolulu at the present time would be to remove a large percentage 

 of her prized vegetation without giving her citizens adequate com- 

 pensation. 



ELIMINATION OF HOST TREES. 



It has been stated under a discussion of clean-culture methods 

 that the elimination of host trees and shrubs in Hawaii is impracti- 

 cable at the present time. Should the Mediterranean fruit fly ever 

 become established in California or the Southern States, wherein there 

 is no such wealth of host fruits and where climatic conditions would 

 assist in control, the elimination of host trees other than the orchard 

 cultures to be protected would play a most valuable part in control 



