UNEXPLAINED MORTALITY. 13 



in 1906, white flies were more abundant in 1!)()7 in this <]J^ov(^ (haii 

 in any other <:j;r(>ve or section in or near Orhiiulo. 



The white-fly hiboratory was located in jijrove No. H durin<; 1906 

 and 1907. This grovo, the property of Hon. J. M. Cheney, is 

 located innnediately south of No. 2. The red Aschersonia was more 

 al)undant on a certain group of tiees in this grove than on any other 

 trees in the locality covered by these observations. The white flies 

 were most abundant in this section of the grove in 1907, while in 

 other sections, where only traces of the fungus occurred, the insects 

 had become very scarce before September 1, 1906, and were least 

 numerous in 1907. 



Grove No. 4 is the "Wilcox Grove," located immediately south of 

 Mr. Cheney's grove (No. 3). The foliage in this grove was only 

 slightly blackened at the time it first came under the observation of 

 the senior author in August, 1906, the insects even then being on 

 the decline in point of numbers. In this grove the fly was so effect- 

 ivel}^ reduced that it did not multiply to the point of slightly blacken- 

 ing the foliage until the fall of 1908. 



Grove No. 5 was laiown as the "William Dennen Estate Grove" 

 and is located about one-half mile south of the city limits, imme- 

 diately south of the Atlantic Coast Line Railroad. This grove was 

 so seriously injured in 1905 and looked so unj)romising in the wdnter 

 of 1905-6 that it was considered inadvisable by those in charge to 

 go to the expense of fertilizing until some satisfactory method of 

 control was discovered. In the spring of 1906, during an unfavorable 

 ])eriod, the grove was sprayed twice, the adults being then on the 

 wing. In this instance spraying was at first believed to be responsible 

 for the cleaning up of the grove, but examination in several groves 

 of the efl*ectiveness of the applications made by the sjime spraying 

 outfit, and the experience of the authors in their experimental work, 

 eliminate beyond doubt the possibility that the two applications of 

 sprays were responsible for the scarcity of white flies. ]\lr. E. II. 

 Walker, chairman of the Orange County horticultural commission, 

 who had general charge of the extensive spraying carried on in the 

 Orlando district in 1906, agrees with the authors in considering that 

 the spraying, whatever its efl^ectiveness may have been by itself, 

 could not have produced such striking results. The first trace of 

 red fungus was found in this grove in the fall of 1908 by the senior 

 author. By this time the white fly had increased to the extent of 

 slightly blackening the foliage of a few trees. The greater efl*ective- 

 ness of the unexplained mortality in this grove (No. 5) as compared 

 with the efl'ectiveness of this factor throughout the city of Orlando 

 was due to the absence of china-trees (Mtiia azcdarach) and umbrella 

 china-trees (Melia ozedarach umbra culif era) in the immediate neigh- 

 borhood. These trees, as explained in previous publications,^ are 



> rUil. 76, Bur. Ent., U. S. Dept. Agr., 1908 (see Chinaborry); JJul. 92, Bur. Knt., U. S. Dept. Agr., 1911 

 (see China-tree). 



