1909.] PUBLIC DOCUMENT -No. 73. 53 



cities and towns we believe that teams are being used more 

 than is necessary, and we shall endeavor in the future to re- 

 duce this expenditure. 



The Wilt Disease of the Gypsy Moth. 

 During the caterpillar season of 1908 we employed experts 

 to investigate the wilt disease of the gypsy moth, looking to the 

 end that this disease, which is probably bacterial, might be 

 propagated and spread artificially. No conclusions definite 

 enough for publication were reached last season. The work 

 will probably be continued in the summer of 1909. 



The FtriTGOus Disease of the Browit-tail Moth. 

 The experiments made under the auspices of this office dur- 

 ing the past year for the purpose of testing the efficiency of 

 the brown-tail moth fungus (Entomophthora Aulicce Eeich.) as 

 a means of producing artificially a wholesale destruction of 

 these insects in badly infested areas, was suggested by the ap- 

 parent success of a similar experiment made during the previous 

 year at Kittery Point, Me. Early in June, 1907, a large arctian 

 larva was found in this locality, freshly killed by the Unto- 

 mophthora, and as soon as the spore-discharge had commenced, 

 several thousand brown-tail larvae were placed in such a position 

 that they would be exposed to it. The infected larvse were 

 then distributed over an area badly infested by brown-tail 

 moths, and allowed to crawl up such trees as were most seriously 

 infested, in order that they might join and mingle with the 

 uninfected larvse. The period of incubation of this disease is 

 about five or six days, more or less, the time varying with the 

 size of the infected individual, the temperature and the weather 

 conditions ; and after this period of incubation within the larva 

 the disease is propagated by an external discharge of minute 

 spores, which, by a special mechanism, are shot violently into 

 the air. A well-grown larva, under favorable conditions, would 

 probably discharge several hundred thousand of these spores, 

 each capable of infecting a fresh larva in case it came in con- 

 tact with one; and among gregarious insects, like the ones in 

 question, the chances of copious infection are very great. 



