1210 



MANUAL OF DETERMINATIVE BACTERIOLOGY 



1. Rimocortius kwanzani Milbrath and 



Zeller. (Phytopath., 32, 1942, 430.) 

 From Kwanzan, name of a variety of 

 flowering cherry. 



Common name : Flowering-cherry 

 rough -bark virus. 



Hosts: Prunus serriilata Lindl. var. 

 Kwanzan, flowering cherry; P. avium L., 

 Mazzard cherry. 



Geographical distribution : United 

 States (Oregon). 



Induced disease : In flowering cherry, 

 tree dwarfed, deficient in lateral 

 branches; bark deep brown, roughened, 

 splitting longitudinally ; internodes short- 

 ened, bunching leaves; leaves arched 

 downward; midribs of leaves split and 

 cracked on under surface. In Mazzard 

 cherry, no manifestation of disease, but 

 carrier condition ; budded Mazzard stock 

 may transmit disease to healthy Kwanzan 

 cherry cions. 



Transmission: By budding, generally 

 even if the inserted bud fails to survive. 



Literature : Milbrath and Zeller, Phy- 

 topath., 32, 1942, 428-430; Thomas, ihid., 

 32, 1942, 435-436. 



2. Rimocortius psorosis (Fawcett) 

 comh. nov. (Citrivir psorosis Fawcett, 

 Phytopath., 31, 1941, 357.) Specific 

 name meaning "of the disease known as 

 psorosis." 



Common name: Citrus-psorosis virus. 



Hosts: RUT ACE AE — Citrus sinensis 

 Osbeck, orange; C. limonia Osbeck, 

 lemon; C. maxima Merr., grapefruit. 



Geographical distribution : World-wide 

 where citrus trees are grown. 



Induced disease: In citrus, small, 

 elongated, light colored areas or flecks in 

 the region of small veins on young, tender 

 foliage; leaves sometimes warped; (chlo- 

 rotic?) clearing of veins, and chlorotic 

 line patterns, sometimes concentric. 

 Outer layers of bark scale away ; depres- 

 sions and deformities appear in bark and 

 wood. Lemons, as a rule, are more tol- 

 erant than oranges and are not subject 

 to the bark changes. 



Transmission : By grafting, including 

 root grafting and patch bark grafting. 

 Not by inoculation of expressed juice. 

 No insect vector is known. 



Literature : Bitancourt et al., Phyto- 

 path., 33, 1943, 865-883; Fawcett, ibid., 

 21t, 1934, 659-668; Science, 92, 1940, 559- 

 561; Phytopath., 31, 1941, 356-357; Faw- 

 cett and Bitancourt, ihid., 33, 1943, 837- 

 864; Rhoads, ibid., 32, 1942, 410-413; 

 Webber and Fawcett, Hilgardia, 9, 1935, 

 71-109. 



Strains : Three strains differing from 

 the type have been recognized. The 

 type, var. vulgare Fawcett, Phytopath., 

 31, 1941, 357, causes psorosis A, the com- 

 mon scaly-bark type of disease, with 

 pustular eruptions of outer layers of bark 

 in limited areas, with or without exuda- 

 tion of gum ; later a drab-gray, cinnamon- 

 drab to rufus discoloration of the wood, 

 accompanied by decline of the affected 

 tree. Others, that contrast with the 

 type, are : 



2a. Rimocortius psorosis var. anulatum 

 Fawcett. (Phytopath., 31, 1941, 357.) 

 From Latin anulatus, with a ring. Caus- 

 ing psorosis B, known from California, 

 resembling zonate chlorosis of Brazil in 

 effects on leaves and fruits. Psorosis B 

 is characterized by rapid scaling of outer 

 bark in continuous areas, progressing 

 rapidly along one side of trunk or branch ; 

 gum exudes in advance of scaling, necrosis 

 follows; large circular discolored and 

 corky spots, sometimes concentric, on 

 fruits and mature leaves; on some fruits, 

 circular or semi-circular furrows and 

 bumps ; rapid decline of the affected tree. 



2b. Rimocortius psorosis var. concavum 

 Fawcett and Bitancourt. (Phytopath., 

 33, 1943, 850.) From Latin concavus, 

 concave. Causing concave-gum psorosis, 

 characterized by concavities of various 

 sizes on trunks and larger limbs of af- 

 fected trees, often by zonate patterns on 

 young leaves during periods of rapid 

 growth. 



