330 BOARD OF AGRICULTURE. [Pub. Doc. 



material were made than in any previous year. In fact, the 

 disease has now been distributed over the entire moth-infested 

 area of the State. In view of the fact that the results of this 

 planting are still problematic, it does not seem advisable to perse- 

 vere in this work. Further investigations show that our knowl- 

 edge of the disease is still fragmentary, and we must wait further 

 development before expending more money. The experimental 

 and scientific side of the work is now being prosecuted systemati- 

 cally by the United States Bureau of Entomology and by Harvard 

 University in co-operation. We append a letter recently received 

 from Professor Wheeler of the Bussey Institution of Harvard 

 University which explains more fully the feeling among scientists 

 in regard to the probability of success in attempting to spread 

 wilt disease of the gypsy moth artificially. Professor Wheeler 

 is not alone in his opinion, for it is shared by the most celebrated 

 scientists abroad and by many prominent entomologists here in 

 Massachusetts. 



"Flacherie" Opinion op Professor Wheeler. 



Bussey Institution, Forest Hills, Mass., Nov. 20, 1912. 



Mr. F. W. Rane, 6 Beacon Street, Boston, Mass. 



My dear Mr. Rane : — In obedience to your request I beg leave to 

 submit to you my opinion in regard to continuing the practice of attempt- 

 ing to spread the wilt disease, or "flacherie," of the gypsy moth cater- 

 pillars by artificial means in the forest lands of eastern Massachusetts. 

 It is obvious that any attempt thus to utilize the wilt disease in practice 

 must be based on a precise knowledge of the methods whereby the disease 

 may be contracted by healthy caterpillars. Although we have good 

 evidence for believing that the disease may be contracted by healthy 

 caterpillars that have fed on the excretions of diseased caterpillars, or the 

 deliquesced portions of caterpillars that have died of the disease, we have 

 at present no data to prove that the disease can be transmitted from 

 diseased to healthy caterpillars by mere bodily contact or by germs borne 

 through the air. Many experiments have been performed for the purpose 

 of proving the method of transmission last mentioned, but these, in my 

 opinion, have given merely negative or highly equivocal results, owing to 

 the fact that the disease, in a mild or latent form, is chronically, and 

 perhaps hereditarily, present in practically all the localities in which the 

 caterpillars occur in eastern New England. The acute and economically 

 important phase of the disease may, therefore, arise through unusual 

 meteorological conditions, or through peculiarities of the plants on which 

 the caterpillars happen to be feeding. Hence, there is no advantage in 



