Studies on the Fire-Blight Organism, Bacillus amylovorus 9 



on terminal shoots of Photinia growing in the nursery at the university 

 farm at Ithaca. On May 28, 1926, twenty-five terminals were punctured 

 with a sterile needle dipped in a bouillon culture of Bacillus amylovorus. 

 Inspection on June 14 showed that twenty-one of the twenty-five inocu- 

 lated terminals had blighted, and some had been killed for a distance 

 of eight to ten inches. Isolation and reinoculation into apple seedlings 

 proved the presence of the fire-blight pathogene. On July 4 the experi- 

 ment was repeated on ten terminals, of which six blighted. One ter- 

 minal continued to die back until a limb three-eighths of an inch in 

 diameter had been killed. In Plate I, 3, is shown a blighted terminal in 

 which the organism died and new shoots arose from the live tissue below. 

 The inoculation was made on July 4, 1926, and the photograph was 

 taken on August 3. 



SUMMARY OF SUSCEPTS 



Either through inoculation and isolation experiments or through 

 identification of the bacteria by means of cultural characters, the fol- 

 lowing .species have been proved suscepts for the fire-blight disease: 

 apple (Pyrus mains, P. baccata, P. coronaria), pear {Pyrus communis 

 and all other species tested), quince (Cydonia oblonga), cherry 5 

 (Prunus avium [Bing and Royal Ann varieties]), plum {Primus 

 nigra, P. domestica, and P. salicina), flowering almond (Prunus triloba), 

 aprieot (Prunus armeniuca), hawthorn (Crataegus oxyacantha, C. 

 oxyacantha var. splendens, and C. crus-galli) , common firethorn (Pyra- 

 cantha coccinea [Crataegus pyracantha]) , June berry (Amelanchier 

 canadensis), medlar -(Mespilus germanica), loquat (Eriobotrya japon- 

 ica), strawberry (Fragaria chiloensis var. ananassa and F. virginmna), 

 rose (Rosa eglanteria, R. blanda, and varieties Fairfax, Tausendschon, 

 Climbing American Beauty, Martha Washington [probably derived 

 from R. cathayensis]), Photinia (Photinia villosa), Japanese quince 

 (Chaenomeles lagenaria), and. spiraea (Spiraea vanhouttei). Species 

 which are probably suscepts but concerning which further investigations 

 are needed, are mountain ash (S orbits aucuparia and S. aucuparia var. 

 laciniata), Christmas berry (Heteromeles arbutifolia), yakimine, apricot 

 plum (Prunus simonii), the Hortulana plum (Prunus hortulana), and 

 additional species of Crataegus. 



5 On June 17, 1030, a twig blight was observed <>n sour cherries (P. ccrasus L.) of the 

 Montmorency variety in several localities in southern Ohio. The symptoms resembled those 

 of tire blight, and cultures yielded nn organism which on beef-peptone agar was indistin- 

 guishable from i:<i<ilhts amylororus. [noculation into ten vigorous apple shoots produced 

 blight in nil of them. The organism was recovered in culture and used a second lime to 

 produce infection on apple shoots. 



