44 NATUEAL CONTEOL OF WHITE PLIES IN PLOEIDA. 



condition in July, but in December the average number of dead 

 larvffi and pupae was found to be 61, live larvae and pupae 11.9, and 

 pupa cases 5.1. ' This would indicate at least a slight blackening of 

 the leaves by the end of the year, judging from the effects of a lighter 

 infestation in the case of No. 4 as noted above. To a casual observer 

 this fairly satisfactory condition might appear to have resulted from 

 fungous diseases. As a matter of fact the fungous diseases had no 

 appreciable effect. A fairly high average number matured per leaf 

 in the spring of 1909, but very few eggs were deposited on the citrus 

 trees. This appeared to be due to the emergence of the insects 

 before the appearance of new gi'owth on the citrus trees and as a 

 consequence the attraction of the adult white flies to other food 

 plants, persimmon and China trees, having new foliage. An examina- 

 tion of a persimmon tree growing in the midst of the citrus trees on 

 this property showed 8 times more larvae and pupae per leaf than on 

 the leaves from surrounding citrus trees. If fungous diseases had been 

 concerned in the reduction of the infestation of the citrus trees the 

 July exaniination of the spring growth would have shown this. The 

 examination of 100 leaves picked at random showed that an average 

 of 0.37 white flies of the first generation had matured and that of 

 this generation an average of 0.15 per leaf showed infection by fungous 

 diseases. These, with a very small average of less than 1 per leaf 

 dying from unexplained causes, represented the entire first generation 

 as shown by the examination of the leaves. 



The July examination of No. 9 showed that an average of 0.2 white 

 fly per leaf of the first generation had matured and that 0.46 per 

 leaf was infected with fungous diseases. This low average of infec- 

 tion could not have had any appreciable effect on the normal increase 

 of the insects, and it is obvious that in this grove the comparative 

 freedom of the foliage from blackening was not due to the fungous 

 diseases. 



The very excellent condition as to white-fly infestation of grove 

 No. 10 during the season of 1910 may be properly credited to the 

 effective work of the fungous diseases after midsumer in 1909. The 

 trees suffered so severely during 1909 from the excessive infestation 

 that their unthrifty condition was noted at the time of the examina- 

 tion in July, 1910. 



In No. 12 it was found, on July 1, that an a\'*^eragc of 0.2 per leaf 

 of the first generation had matured, while 0.74 forms of this generation 

 showed fungous infection. As shown by Table II, the reduction in the 

 number of the insects in this gi'ove in 1908 was due almost entirely 

 to an excessive rate of mortality from unexplained causes, fungous 

 diseases being comparatively insignificant. As regards the cause for 

 the failure of the live insects found in December, 1909, to multiply 

 normally. No. 12 must be classed with No. 9. In both these cases 

 the explanation is probably similar to that in the case of No. 8. 



