66 NATURAL CONTROL OF WHITE FLIES IN FLORIDA. 



It appears that the great hmnidity, after tlie introduction of Sep- 

 tember 11, was not a condition which woukl promote fungous develop- 

 ment. The increases in the average number of fungous pustules per 

 leaf are, as a rule, inconsistent, in series A and B, whether the data 

 be examined from the standpoint of the attempts made to spread the 

 infection or from that of climatic conditions. One exception is 

 found in the rapid increase between the exaniination of August 14 

 and tliat of September 11 for both series. This most important 

 increase of the year appe'ars to be entirely uninfluenced by the 

 attempts to spread the infection, since the fungous pustules in series B 

 increased at practically the same rate as in series A. The pustules 

 in series A increased about 200 per cent between July 9 and July 24, 

 when practically uninfluenced by artificial spreading of infection, 

 while the pustules in series B increased only about 60 per cent. 

 Between July 24 and August 14 the attempt to assist natural means of 

 spread was followed by a 46 per cent increase, while without any 

 effort in this direction the natural spread in series B amounted to a 

 200 per cent increase in the number of fungous pustules. 



Notwithstanding the foregoing inconsistencies the records show 

 that after the initial introduction the fungous pustules multiplied 

 about 10 times (964 per cent increase) in series A and about 6 times 

 (623 per cent increase) in series B. It is not impossible that such a 

 difference as this in the rate of multiplication might be found in two 

 arbitrarily selected groups of trees treated identically as regards 

 fungous introductions. We may, however, fairly give the fungous 

 diseases the advantage of the presumption that the difference noted 

 is due to the artificial spreading of the infection. The question then 

 arises. Did this difference result in any practical benefit to the trees ? 



On June 30 an examination showed an average of 59 live larvae 

 and pupa3 per leaf in the experimental block; on July 24, 21.5 per 

 leaf; on August 27, 43.7 per leaf on old mature growth and about 350 

 larvae per leaf on the newer summer growth, and on October 26 an 

 avei'age of 27.8 live per leaf. The last estimate was based on 10 

 typical leaves which averaged 27.5 red-fungus pustules per leaf and 

 10.4 pupa cases. Wliile this examination was not extensive enough 

 to compare with those the results of which are given in Table X, a 

 summary showing more live insects in the leaves showing the most 

 fungous infection is noteworthy. 



Five leaves with greatest nmnber of red-fungous pustules, averaging 47.6 per leaf, 

 36 live per leaf. 



Five leaves with least number of fungous pustules, averaging 7.4 per leaf, 19.6 live 

 per leaf. 



It is probable that more adults migrated from the surrounding 

 trees to the experimental block and from trees of series A to series 



