42 



State University Experimental Station. 



M. Danysz treats at length also of the muscardine on the hedge chafer 

 or June bug (Melolontha vulgaris). This fungus disease is called by M. 

 Giard Isaria densa, and by Messrs. Prillieux and Delacroix Botritus tenella. 

 It is also called the rose-colored muscardine, to distinguish it from other 

 similar fungus diseases. The white grubs or larvce of the hedge chafer pre- 

 sent a rose color when dead from this disease. In dry and sandy soils the 

 bodies of the grubs so killed are hard, brittle, and covered with fine down, 

 excepting on the head and legs. In wet, clayey soils the fungus, besides 

 the white shroud, sends out numerous prolongations sometimes 2 or 2J inches 

 in length, which hold together pieces of earth, roots, and other grubs. These 

 dead and mummified grubs are found at a depth of 8 to 12 inches. In the 

 beetle the white covering occurs only on the ventral surface of the head, 

 thorax, and sometimes the end of the abdomen. The fungus becomes easily 

 transmissible only when its spores are matured, and it can only be used in 

 this state to spread contagion. Wind, rain and living beings are the agents 

 for spreading the disease, by scattering the spores. 



Not much success has yet been had in the artificial dissemination of this 

 disease in the field, but these poor results are due only to insufficiently 

 studied methods of procedure. The destruction of beetles and grubs by 

 natural epidemics of muscardine being a fact, it does not seem impossible to 

 propagate these diseases artificially. From researches made by Dufour, it 

 is proved that spores collected from dead insects are more virulent than 

 those developed from artificial cultures. Laboratory experiments by Dela- 

 croix and others have shown good results. Forty to fifty per cent, of the 

 beetles treated succumbed. The experiments so far have been insufficient, 

 and the following points must yet be determined: (1) Composition and 

 preparation of nutritive media that will give the greatest virulence and the 

 greatest number of spores; (2) method of using these spores to contaminate 

 the greatest proportion of the subjects treated; (3) the stage of develop- 

 ment of the insects most favorable to infection; (4) the method of proced- 

 ure to obtain the virus at the lowest price. 



M. Danyz also recommends that every farmer or commune set apart a 

 small trial field in which to propagate the muscardine on the white grubs, 

 and to proceed carefully, observing everything bearing on the subject. In 

 the following year adjoining fields should be infected from the trial field, 

 and this should be kept up for three years. He thinks that one of the most 

 important factors toward the ultimate success of the muscardine as a white- 

 grub eradicator is its use by all cultivators. 



It is probable that in whatever soils it can develop the muscardine lives 

 in the ground in the state of a saprophyte; that it first attacks subjects 

 most disposed to contract the disease, and that, having regenerated its viru- 

 lence in passing through the bodies of the first white grubs attacked, it be- 

 comes, or rebecomes, a parasite. By continuing to infect the June bugs and 

 their larvae by means of artificial cultures, the virulence of the fungus can 



