December, '14] GLASER: FUNGOUS DISEASES 475 



(4) ''Laboratory experiments can be made to prove that artificial 

 infection accomplishes results upon bugs confined in cramped quarters 

 and without food, but in the field, where fresh and usually drier air 

 prevails and food is abundant, an entirely different situation is pre- 

 sented." 



In 1912, Morrill and Back performed a large series of experiments in 

 Florida to determine whether or not fungi could be used artificially in 

 suppressing the white fly in the citrus groves. It has been known that 

 fungous diseases are very important factors in the natural control of 

 this insect. The most important species of fungi in this respect are 

 Mgerita wehberi Fawcett, the brown fungus, Aschersonia aleyrodis 

 Webber, the red fungus, and Aschersonia flavocitrina, the yellow 

 fungus. 



In attempting to use the above fungi artificially IVIorrill and Back 

 concluded that: 



(1) "The fungus parasites thrive only under suitable weather 

 conditions during a period of about three months each year; generally 

 speaking the summer months in the case of the two Aschersonias and 

 the fall months in the case of the brown fungus. 



(2) "Under natural conditions, without artificial assistance in 

 spreading, the fungi have ordinarily, in favored localities, controlled 

 the white fly to the extent of about one-third of a complete remedy 

 through a series of years. 



(3) "The infections secured by artificial means of introducing 

 fungi, while successful in introducing the fungi, have thus far proved 

 of little or no avail in increasing their eflficacy after they have once 

 become generally established in a grove. 



(4) "Experiments by the authors, and by citrus growers in coopera- 

 tion with the authors, involving the treatment of thousands of trees 

 with suitable "checks" or "controls" have shown that when fungus 

 (red or yellow Aschersonia) even in small quantities is present in a 

 grove, there is no certainty that from three to six applications of fungus 

 spores in water solution will result in an increased abundance of the 

 infection on the treated blocks of trees by the end of the season. In 

 some of the most important and carefully planned and executed experi- 

 ments, the fungus has increased more rapidly in sections of the groves 

 which were not sprayed with spore solutions than in the experimental 

 blocks." 



We must now consider Entomophthora aulicce, the brown-tail fungus, 

 which is the only case familiar to me where an artificial use of a fungus 

 has proved successful to a certain extent. Speare and Colley, the 

 authors of a paper on this subject in 1912, say that it can not be re- 



