Studies on the Fire-Blight Organism, Bacillus amylovorus 5 



showing a blighted twig. Munn (1918) found that strawberry flowers 

 woulfl blight if they were sprayed with a culture of B. amylovorus or 

 if a platinum needle previously dipped into the culture was rubbed 

 over the "nectarial surfaces"; leaves failed to blight when drops of a 

 cultural medium carrying the bacteria were placed on them. Munn 

 states that he has not seen strawberry blight occurring naturally out of 

 doors. 



In 1925 Waite reported that he had obtained typical fire-blight symp- 

 toms by inoculating the cut surface of a mature Winesap apple. Also, 

 by smearing the cut ends of dormant pear and apple twigs and placing 

 them in water under a bell jar, blight cankers were produced. Semi- 

 dormant rose cuttings were infected, but with some difficulty. 



In the same year, Reimer (1925) reported his extensive tests on 

 the resistance of various species of pear to blight. The most resistant 

 appear to be wild forms of Pyrus ussuriensis, an oriental species. P. com- 

 munis, the species on which most of our pear trees are grafted, is the 

 most susceptible. P. calleryana, which is highly resistant to blight, is 

 recommended at the present time for Oregon. Reimer has tested all 

 the known species of pear and has found individuals in each species 

 that will become infected by the fire-blight pathogene. 



In 1926 Anderson listed Spiraea sp. as a suscept for fire blight in 

 Maryland. Two years later, Rosen and Groves (1928) reported that 

 detached twigs of Spiraea vanhouttei Zabel, Chaenomeles lagenaria 

 Koidz., and rose terminals of the variety Fairfax, were successfully 

 inoculated in the greenhouse with B. amylovorus. Natural infection 

 was reported on Burbank plum (Prunus salicina Lindl.). 



In addition to the above-named hosts, other species have been shown to 

 li arbor the blight organism in their floral parts without exhibiting 

 symptoms of disease. Gossard and Walton (1922: 99) conclude: "These 

 results mean that the blight organism is capable of living in peach, plum 

 and cherry nectar for five days or probably more. . . ." The writer 

 has reexamined some of the reported cases, and as a result of experi- 

 mental work has added several new species to the list of suscepts. 



INOCULATIONS on hawthorn 



In the region near Skaneateles, New York, where there are numerous 

 hedges of Crataegus oxyacantha, the writer noticed what appeared to 

 be fire blighl on many trees in 192:5. [solations were made in the 

 summer of 1924, and these cultures were used to inoculate apple seed- 

 lings during the winter of 1925. Infection was readily obtained. 



Inoculations were made also in July, 1925, on five water sprouts 

 growing on a large C. oxyacantha tree at Ithaca, New York. All five 



