62 



NATURAL CONTROL OF WHITE FLIES IN FLORIDA. 



blocks of trees in this grove (fig. 1) were sprayed as indicated with 

 a spore mixture made by using about 1/200 pustules of red Ascher- 

 sonia to each 4 gallons of water.' 



On August 21, almost before the introduced fungous spores had 

 had an opportunity to mature into pustules, 27.6 per cent of the 185 

 trees sprayed August 10 were visibly infected with red Aschersonia, 

 and 18.6 per cent of the 354 trees sprayed on August 11, while 15.5 

 per cent of 252 check trees showed the presence of fungi. A fungous 

 inventory of this grove made during the following December showed 

 the general infection represented in figure 1. A study of the distri- 

 bution and comparative abundance of the fungus as indicated shows 

 that it had no relation to the trees sprayed and that the spread from 

 the middle of August on was entirely independent of any practical 

 influence of the introduced spores. In fact some of the very best 

 infections were on trees that were not sprayed. 



A count of leaves picked promiscuousl}^ from the trees on April 30, 

 1909, gave data included in Table X.^ 



Table X. — Red Aschersonia; averages -per leaf on sprayed and unsprayed blochs. 



In Table X the forms recorded, aside from fungous infections, rep- 

 resent the total number of white flies surviving the winter. The 

 spring mortality referred to is mostly the same as that discussed 

 under the head of climatic conditions. The predaceous tlu'ips men- 

 tioned elsewhere was also concerned in this mortality to some extent. 

 It is evident from the data presented that absolutely no tangible 

 benefit resulted from the attempt to spread tlie infection. A grove 

 immediately south of the experimental grove, similarly infested 

 with red fungus but in which no attempt was made to spread the 

 infection, developed even more fungus than did the sprayed trees. 

 An examination of 100 leaves picked at random in this grove showed 



1 Sprajing began in the afternoon of Aug. 10, 1908. About 2 inches of rain fell during the morning and 

 the afternoon was cool; the temperature for afternoon and nighi ranged from 74 degrees to 71.5 degrees F., 

 while the humidily ranged from 92 decrees to .82 degrees and up to 99 degrees, where it remained close 

 to 100 until 7 a. m., Aug. 11, when it gradually dropped to 03 degrees by 1 p. m., then rose suddenly to 

 94 degrees by 4 p. m., remained between 94 and 95 degrees for about one hour, suddenly dropped to 90 

 degrees, and then rose to 99 degrees and remained at 100 during the night of Aug. 11. The tern peratureat 

 4 a. m., Aug. 11, was 71.5 degrees F., gradually rose to 89 degrees F. by 12 m., and remained there until 

 2.30 p. m., then suddenly dropped to 74 degrees F. by 3.30 p. m., and then slowly dropped until 71 

 degrees F. was reached at 4.30 p. m. On Aug. 12 temperatiu-e rose to 92 degrees F. by 2 p. m. Subse- 

 quent conditions were very favorable for the spread of fungus. 



2 One hundred leaves were picked from each block, or 800 in all. The leaf averages are proportionally 

 lower than in the records in Table II, since leaves were taken from all growths at random. 



