KEENEL-SPOT OF THE PECAN AIS^D ITS CAUSE. 9 



The surface of the kernels was wiped with absorbent cotton satu- 

 rated with a 1 to 1,000 solution of mercuric chlorid. Then with a 

 flamed scalpel the top of the spot was cut off. A section of the re- 

 maining spot with its adjacent healthy tissues was removed with the 

 same scalpel. This was immediately transferred with a sterile needle 

 to a Petri dish containing beef or corn-meal agar. 



This method of technic eliminated the danger of killing by the 

 absorption of mercuric chlorid any parasite or saprophyte that might 

 happen to be in the affected tissues, and at the same time it reduced 

 the chances of outside infection to a minimum. By employment of 

 the above method numerous Petri dish cultures were made, in order 

 to study the flora of the diseased spots. 



The use of kernels having several spots whose internal structures 

 Avere discolored very generally resulted in producing, in cultures, 

 colonies of fungi and bacteria. This was to be expected, since several 

 forms of saprophytic fungi and bacteria readily obtain entrance to 

 plant tissues which have died from any cause. This is especially true 

 of tissues which have died from mechanical injury, since they are not 

 already inhabited with microorganisms. Eight forms of fungi and 

 three of bacteria were quite constant, but no single one predominated 

 except a bacterial form with a light-yellow color. This is possibly 

 the same form referred to by Rand in his investigation previously 

 cited. 



Out of 58 spots taken from Curtis nuts that had been confined in 

 cages with several specimens of Nezara viridula for a period of ap- 

 proximately two months, 35 produced colonies of bacteria, 19 grew 

 fungi, and 4 remained sterile. It should be recorded here that the 

 kernels of these nuts were so severely injured by the constant feeding 

 of the bugs over an extended period that many blackened and inter- 

 nally discolored sunken spots resulted. The kernels were all dwarfed 

 and shrunken, and the shucks of none of them opened normally. The 

 check nuts and also uncaged nuts on the same trees were well filled, 

 and their shucks opened at the normal time for the Curtis variety. 



Cultures were made of 65 s^^ots taken from moderately diseased 

 Curtis nuts. Colonies of bacteria were formed in 28, 9 produced 

 fungi, and 28 remained sterile. 



Of spots taken from Schley pecans that were confined with bugs for 

 a period of 4 or 5 weeks 111 were plated on corn-meal agar. Of these, 

 6 produced colonies of bacteria, 6 grew fungi, and 99 were sterile. 



Of spots from Frotscher pecans, grown near Thomasville, Ga., 21 

 were cultured. Fungi grew on 9 of the spots, none produced bac- 

 terial colonies, and 12 were sterile. 



Nuts were selected from the same Schley tree on which the cages 

 were attached. Cultures were made of 48 separate spots. The re- 



