4 BULLETIN 611, U. S. DEPARTMENT OF AGRICULTURE. 



planting extensively I should expect that disease to be serious. That would be 

 my forecast of the matter. The humidity and cloudy weather in the East 

 ought to be more favorable to the disease than the climate of California. 



There is no reason to suppose that blight will not appear wherever 

 Persian walnuts are grown. 



THE DISEASE IN THE EASTERN STATES. 



During the first week in June, 1916, a trip was made by the writer 

 to various points in Delaware, New Jersey, and Pennsylvania where 

 bearing walnut trees were known to-be located. On practically every 

 tree that had a crop the nuts were found to be spotted in a manner 

 very characteristic of bacteriosis (PI. I). The lesions at this time 

 were small and superficial in character, rarely extending more than 

 2 to 3 millimeters (about one-tenth of an inch) into the husk. A 

 number of specimens were collected and cultures obtained. 



The technique used consisted in washing the nuts with soap and 

 water, sterilizing the surface with an alcoholic solution of mercury 

 bichlorid for five minutes, and then washing in distilled water. 

 After this treatment the epidermis of the diseased spots was removed 

 carefully with a sterile scalpel and bits of subepidermal tissue trans- 

 ferred to tubes of melted beef agar, agitated, further diluted in a 

 second and third tube of the same media, and poured into Petri 

 dishes. About 15 attempts were made, in practically all of which 

 bacterial colonies of a similar type appeared on the plates in from 

 two to four days, and the plates from the third dilutions usually 

 contained colonies which were so few as to allow transfers to be 

 made to tubes without difficulty. During the first week in August 

 a series of inoculations was made on the nuts and twigs of a certain 

 mature tree at Lancaster, Pa., which was said to be a seedling of 

 Rush. The husks of 24 young nuts entirely free from any trace of 

 the disease were inoculated (1) by spraying with a suspension of 

 the germs in rain water, (2) by smearing on the culture, and (3) 

 by puncturing with an infected needle. Several untreated nuts were 

 tagged as controls. At the same time five young, tender, growing 

 twigs 5 to 10 millimeters in diameter were inoculated with the germs 

 about 6 inches from the tips by making several punctures in each 

 with an infected needle ; one twig was punctured with a sterile needle 

 as a control. The organisms used in these experiments were all from 

 pure cultures on beef agar and obtained as previously described. 



A month later (Sept. 5, 1916) it was found that 21 of the 24 nuts 

 inoculated had developed the disease and 3 showed no trace of it; 

 the untreated nuts were perfectly clean. Of the five twigs inocu- 

 lated, all had developed cankers from 5 to 10 mm. in length and from 

 2 to 5 mm. in width. Plate II shows one of the nuts 30 days after 



