536 



JOURNAL OF ECONOMIC ENTOMOLOGY 



{Vol 8 



the wounds in the bark produced hy the insect are much discolored or 

 dead. The diseased areas range generally' from one-fourth of an inch 

 to an inch in diameter, while the bark within these limits varies from 

 purplish or reddish-brown to pale brown, depending a^pparently on the 

 extent and age of the infection. Usually most of the affected spots 

 are circular or somewhat oval in form, and occasionally there -is a 

 large irregular extension of the original infected area as if there had 

 been a renewal of activities by the infectious agent. The bark within 

 the area of infection is generally slightly depressed and may also 

 be separated from the sound bark by a distinct line or narrow crack. 

 In more advanced stages cracks develop, separating the dead area from 

 the surrounding living tissues, and there is formed a core which adheres 

 loosely to the wood, affording attracti^-e situations for the woolly aphis. 

 From the wounds made by the insect, located as a rule in the center 

 of the diseased areas, one may observe in April or j\Iay more or less 

 flowing of a gummy, reddish-colored liquid, which on drying leaves a 

 resinous product about the orifices of the punctm^s. In their exter- 

 nal appearances and effects these cankers resemble superficially cer- 

 tain stages of the New York apple-tree canker {Sphoeropsis malorum 

 Pk.) or the blight canker of apple trees {Bacillus amylovorus (Burr.) 

 de Toni) . 



Our investigations on the tree cricket with reference to this dis- 

 order of apples have been along three lines, (1) to identify the infec- 

 tious organism of the apple bark, (2) to ascertain the habits of the 

 tree cricket to determine in what ways it may act as a carrier of 

 the disease and (3) to make experimental attempts to reproduce the 

 disease in apples by using the crickets as carriers of the spores. These- 

 studies were conducted jointly by the Departments of Botam^ and 

 Entomology of the Geneva Station, the former department directing^ 

 the work involving the determination of the fungi and the ctiltural and 

 experimental operations with the disease organisms. 



Idextificatiox of CArsAL Agent of Bark Disease 



The primary steps in this cooperative effort involved the deter- 

 mination of the causal organism, which was essential before there 

 could be a really intelligent understanding of the exact role of tree 

 crickets in the dissemination of the disease. Cultural and micro- 

 scopical studies conducted to this end have revealed the interesting 

 fact that the causal agent of the bark trouble in New York was, in 

 the majority of cases, neither the New York apple canker {Spharopsis 

 malorum) nor the fire-blight canker (Bacillus amylovorus), as formerh- 

 supposed, but a species known as Leptospharia coniotlnjrium (Fckl.) 



