328 Journal of Agricultural Research voi. iii. no. 4 



that it takes repeated attacks to infest grapefruit, lemons, and oranges 

 in Hawaii and that the pulp of these fruits is infested usually only after 

 the fruits are very ripe; in fact, not until they become much riper than 

 commercially-grown oranges usually are allowed to become in either 

 California or Florida, unless exception be made of such varieties as late 

 Valencias. The relatively small number of adult fruit flies entering a 

 block of citrous trees would find it very hard to establish themselves, 

 since the numbers would be so insignificant as compared to the fruit 

 surface suitable for oviposition that each female would be less likely to 

 oviposit repeatedly in the same puncture. Her progeny would therefore 

 meet with almost insurmountable difficulties in reaching the pulp. 



It has been stated that in Hawaii citrous fruits offer themselves for 

 attack over several months and that they are not subject to serious 

 attack until they have turned or are about to turn color. It is a well- 

 known fact among horticulturists that in very equable climates the pulp 

 of oranges may be ripe enough to eat while the rind is still very green. 

 In Florida and California this is not so true. One has only to visit the 

 packing houses in either State to be convinced that much fruit is gathered 

 for the early trade in a semiripe condition, or at least when the rind is 

 quite green in color. The writers feel safe in saying that market condi- 

 tions are such that early fruit is placed on the market at the earliest 

 possible moment, in order that high prices may be secured. The fear of 

 unseasonable frost and freezes has made it difficult for those who have the 

 interests of the citrous industry at heart to prevert the shipping of too 

 green fruit. It would seem that with a reasonable expenditure of more 

 care than labor, citrous groves in either Florida or California can be 

 made so well protected from the Mediterranean fruit-fly attack that such 

 few flies as enter them during the fall will find the early fruit, upon which 

 they can work because of its degree of ripeness, picked before they are 

 able to injure it to any extent. The cold weather will protect the later 

 fruit by rendering the fruit flies inactive, and by the time the spring 

 temperatures become suitable for fly activity the bulk of the fruit will 

 have been marketed and the numerical abundance of the adult flies 

 greatly lessened. 



In addition, if it becomes necessary, as a result of unfavorable condi- 

 tions, to use artificial means of control, spraying with a cheap poisoned 

 bait will be a practical method of reducing the number of adults. If the 

 writers under most adverse conditions can reduce by spraying the num- 

 ber of adult fruit flies over 50 per cent in one city block in Honolulu, 

 into which it has been proved that adults are continually migrating, it is 

 only reasonable to expect that the same good results as have been 

 secured in South Africa, where fruit has been protected by spraying, will 

 follow spraying in either Florida or California, where outside sources of 

 infestation can be so easily controlled. 



