30 



BULLETIN 640, U. S. DEPARTMENT OF AGRICULTURE. 



HOST CONDITIONS IN THE COUNTRY. 



While host conditions within the city limits render useless such 

 artificial control measures as can be applied under existing condi- 

 tions, country host conditions are almost, if not quite, as discour- 

 aging. Here the fruit fly has been able to establish itself, often 

 miles from towns, in some one or more of its hosts which have es- 

 caped cultivation and have spread over uncultivated and uncultiva- 

 ble areas. Of such hosts, the common guava is the most abundant. 

 It has taken possession of the roadsides, pastures (as shown in fig. 

 26), vacant town lots, mountain gulches and hillsides, and even 

 crevices on precipices. So easily does the plant grow from seed and 

 so thoroughly distributed are its seeds by cattle, birds, and man, 



Eig. 26. — Men cutting down a dense thicket of guava bushes. In such a guava scrub ripening fruits are 

 present throughout the entire year and in them the Mediterranean fruit fly breeds, often far from culti- 

 vated fields. (Authors' illustration.) 



that it is seldom that in the lowlands, except in very arid areas, a 

 bush can not be found within a stone's throw. In pastures and moun- 

 tain gulches up to an elevation of at least 1,500 feet, particularly 

 where sheltered from strong winds and well watered, the guavas may 

 become very treelike and form dense thickets. While the guava 

 fruits most heavily during the spring and fall months, the bushes 

 are continuously in bloom and ripen a sufficient number of fruits to 

 support the fruit fly every month in the year. 



Second to the guava as a host occurring in the wild uncultivated 

 areas is the prickly-pear cactus. Though the fruits of this plant are 

 not preferred by the fruit fly, they are sufficiently infested in the 

 absence of more favored hosts to serve as food, and, as in the case of 

 the guava, there is almost no time during the year when a few ripe 

 fruits can not be found in any cactus scrub. 



