60 NATURAL CONTROL OF WHITE FLIES IN FLOEIDA. 



spores and mycelia. The best general infection by browTi fungus 

 which has come under the observation of the authors was one 

 secured in a grove ^ of Mr. W. C. Temple at Winter Park, by Mr, 

 Frank Sterling of Deland. The ordinary method of spraying spores 

 was used. The spraying was done between October 2 and 16, 1908. 

 Doubtless there was more or less secondary spreading in the fall, but 

 there was no appreciable spread in 1909 before April 23, when the 

 records were made. At that time brown fungvis was found to be 

 present on 7 per cent of the leaves, averaging 23 pustules per infected 

 leaf or 16 pustules for the entire lot of 100 leaves examined. 



As regards the extent of infection attainable by methods herein 

 discussed, the authors consider the results far from satisfactory. The 

 dipping of white-fly infested branches in water mixtures of spores of 

 Aschersonia and ground-up leaves infected by brown fungus would 

 appear to represent a maximum of favorable mfluences so far as prac- 

 ticable methods of introduction or spread are concerned, and the fail- 

 ure to secure more than a slight infection, comparatively speaking 

 under any conditions mdicates the relative insignificance of human 

 efforts as compared with natural methods of spread. 



PRACTICABILITY OF INCREASING THE EFFICACY OF FUNGOUS PARASITES. 



The efficacy of the fungous parasites may be said to be increased, in 

 a broad sense, whenever they are introduced or even spread naturally 

 mto white-fly-infested citrus groves in which they previousl}^ did not 

 exist. The subject to be considered here, however, relates to the ordi- 

 nary meaning of the expression "increasing the efficacy" after the 

 initial introduction has alread}^ been accomplished. Apparently there 

 are only two opportunities for effort in tliis direction. The first con- 

 sists in producing conditions more favorable for the development of 

 the fungous parasites and the second consists in artificially spreading 

 the infection. 



IMPROVEMENT OP CONDITIONS FAVORING THE DEVELOPMENT OF FUNGOUS PARASITES. 



A line of work which naturally suggests itself in connection with an 

 investigation of this kind is the improvement of conditions favoring 

 the development of fungous parasites. Preliminary work in spraying 

 trees with clear water m the absence of regular rainfall gave no 

 promise of benefit. Common observations made hi hammock groves 

 in Lee and Manatee counties are sufficient to prove the futility of 



» No examination of this grove was made prior to Deo. 8. 1908, but since no brown fungus was found in 

 several surrounding groves, since none was known to occur nearer than 5 miles, and since no previous 

 attempt had been made to introduce it, it was presumed that this fungus was introduced by Mr. Sterling. 

 On the other hand, yellow and red fungi sprayed at the same time were presumed net to have been suc- 

 cessfully introduced or spread by this application, since on the opposite side of the road a grove in which 

 no artificial introduction had been made was found to have an average of twice as many red-fungus pus- 

 tules and six times as many yellow-fungus pustules per leaf. 



