04 FUMIGATION FOB THE CITRUS WHITE FLY. 
favors the effectiveness of fungous and bacterial diseases, all give 
basis for the hope that complete control by natural enemies will be 
the eventual conclusion of the white-fly problem. A thoroughly 
scientific and practical investigation, however, can not lead to Lasting 
benefits if the conclusions represent merely desired results and are 
unsupported by sufficient evidence and experience. While a great 
deal has been learned concerning the fungous diseases of the white 
fly, the present investigations of this Bureau have not thus far shown 
that any method can be relied upon to materially assist nature in 
controlling the pest to the point of preventing all or nearly all of its 
injury. The dissemination of these diseases is readily accomplished 
under certain favorable conditions, but how far artificial dissemina- 
tion, at its best, with our present methods goes toward the successful 
control of the white fly is still problematical. 
Manatee County is the only large orange-growing district where the 
fungous diseases have proved of much assistance. Data obtained 
from many orange growers and personal observation by the writer 
and other entomologists connected with the Bureau of Ento- 
mology indicate that the fungi, without artifieal aid, reduce the 
injury from the white fly about one-third. Undoubtedly without the 
aid of these fungous friends the damage in Manatee County would 
average more than 50 per cent. With this as a minimum estimate. 
the average damage in Manatee County, allowing a benefit of one- 
third from the fungi, amounts to 34 per cent. One year in three, it is 
the experience of the growers in this county, the fungi have so 
thoroughly cleaned up the pest that the fruit is clean and requires no 
washing. The following year the insects are in the ascendency and 
the fruit and foliage become blackened with sooty mold to as great 
an extent as, can be observed anywhere in the State. This is due to the 
fact that the fungi have diminished the white flies the previous year to a 
point where they cease to flourish. Late in the second year, however, 
with the fly abundant . the fungous enemies develop rapidly. The third 
year the effect of the blackening of the foliage is apparent in a greatly 
reduced crop, while during this year the fly is again reduced to a negligi- 
ble quantity, permitting a good crop of fruit t<> set and remain clean 
from sooty mold during the following season. The above is the usual 
course followed in individual groves. Considering the county as a 
whole in 1906, fully three-fourths of the groves were so free from sooty 
mold as to require no washing of the fruit. It was generally con- 
sidered that this condition had never before been equaled since the 
white fly first obtained a foothold in this county. In one case, how- 
ever, it was claimed by one of the leading orange growers that an 
isolated grove had become practically clean through some unknown 
agency, the prevailing fungous diseases not being present in sufficient 
abundance 1 to accomplish any noticeable result. Nevertheless, the 
fungous enemies referred to were undoubtedly of prime importance 
