43 



A point tbat lends color to the hypothesis that the beetle is capable 

 of being a primary enemy is that congeneric species are known to 

 attack healthy trees, and hitherto, so far as the writer can learn, no 

 fungous disease has ever been associated with any of them, the same 

 being true of other species of beetles related zoologically or of similar 

 habits. The beetles were found to continue living in dead and dry 

 limbs nearly or quite a year old, and the presence of a fungous disease 

 could not be detected in them when examined in the Division of Vege- 

 table Physiology and Pathology. There were also on the limbs exam- 

 ined numerous holes from which the insects had issued and where the 

 fungus had not been present. The cankerous spots were almost inva- 

 riably attacked by the weevils, and we have the testimony of Professor 

 Piper that the " black spot" 1 was actually detected in these places. 



It is hoped that another season may see these points made clear. 



PARASITIC ENEMIES. 



From the material in which the parasites were first detected thirty 

 specimens of Chalcidids and one beetle were reared during the week 

 ended April 12. Of this lot 17 were true parasites and 13 were hyper- 

 parasitic. The primary parasite of this lot was identified by Mr. Ash- 

 mead as an undescribed species of Dinotus, and of a subsequent 

 rearing as Chiropachys colon Linn., a well-known parasite and efficient 

 destroyer of the fruit-tree bark-beetle (Scolytus rugulosus). The sec- 

 ondary parasite is Asecodes albitarsis Ashm. 



METHODS OF CONTROL. 



This apple-tree borer may prove a difficult insect to successfully 

 combat unless future observation should show that its attack is mainly 

 secondary to and dependent upon that of the fungus. In case it is 

 shown that the insect is not dependent upon the fungus and that it 

 attacks vigorous, healthy growth, insecticides and other direct reme- 

 dies will be necessary. 



From the general manner of the insect's work, it should prove ame- 

 nable to the same treatment as that outlined for the fruit-tree bark- 

 beetle in Circular No. 29 (2d ser. ? pp. 7, 8) of this Division. Clean cul- 

 ture would, of course, be the first requisite. The use of mechanical 

 barriers and deterrent washes, employment of girdled trap-trees, and 

 the use of kerosene emulsion or creosote oil as insecticides are among 

 the remedies advised against the bark-beetle. 



It will be noticed that Mr. Kerr ascribed the immunity of his trees 

 from attack to an annual wash of lye applied to the trunks and limbs. 

 Mr. Palmer states that a wash, composed of lime, soap, and carbolic acid 

 is effective if applied early in spring (in British Columbia) and renewed 

 at the end of May. 



1 As this bulletin is going to press Professor Piper writes that the fungus in ques- 

 tion is Macrophoma currispora, recently described by Dr. C. H. Peck, from British 

 Columbia (Bui. Torrey Bot. Club, Jan., 1900, p. 21). 



