FAMILY CHLOROGENACEAE 



1153 



injury and heat treatments cure peach- 

 rosette disease only in recently infected 

 trees. 



Literature: Kunkel, Phytopath., 26, 

 1936, 201-219, 809-830; in Virus Diseases, 



Cornell Univ. Press, Ithaca, N. Y., 1943, 

 63-82; McClintock, Jour. Agr. Res., U, 

 1923, 307-316; Phytopath., 21, 1931, 373- 

 386; Smith, U. S. Dept. Agr., Div. Veg. 

 Path., Bull. 1, 1891. 



Genus III. Morsus gen. nov. 



Alfalfa-Dwarf Group; viruses inducing diseases characterized in general by sud- 

 den wilting and death or by gradual decline of vigor with foliage of darker green 

 color than normal. Vectors, like those of the typical yellows subgroup, cicadellid 

 leafhoppers so far as known. Generic name from Latin morsus, sting or vexation. 



The type species is Morsus suffodiens spec. nov. 



Key to the species of genus Morsus. 



I. Affecting alfalfa and grape. 



1. Morsus suffodiens. 

 II. Affecting tobacco. 



2. Morsus reprimens. 

 III. Affecting elm. 



3. Morsus ulmi. 



1. Morsus suffodiens spec. nov. From 

 Latin suffodere, to sap or undermine, in 

 reference to process leading to sudden 

 collapse of long infected, but sometimes 

 not obviously injured, grape vines as well 

 as to progressive decline in size of in- 

 fected alfalfa plants, the foliage of which 

 may remain green to the last. 



Common names: Alfalfa-dwarf virus, 

 lucerne dwarf -disease virus, virus of 

 Pierce's disease of the grape, virus of 

 Anaheim disease. 



Hosts : LEG UM INOSAE—Medicago 

 sativa L., alfalfa (lucerne). VITA- 

 CEAE — Vitis vinifera L., grape. 



Geographical distribution: United 

 States. 



Induced disease : In alfalfa, leaves 

 small but green, plant progressively 

 smaller, wood of I'oots discolored yellow, 

 transpiration decreased; wilting may oc- 

 cur; starch of root diminished; plant 

 eventually succumbs, thinning stand 

 prematurely. In grape, dark green color 

 of leaves retained along veins, not be- 

 tween them, or no abnormality in appear- 

 ance of foliage ; wilting and sudden death 

 of plant in summer of second year. In 

 late summer of first year, there may be 



dying leaf margins and dying back of cane 

 tips. 



Transmission : By budding and root 

 grafting. By leafhoppers, Draeculace- 

 phala minerva Ball, Carneocephala Julgida 

 Nott., C. trigultata Nott., Helochara delta 

 Oman, Neokolla circellata (Baker), N. 

 gothica (Sign.), N. confluens (Uhler), 

 N. heiroglyphica (Say), and Cuerna oc- 

 cidentalis Oman and Beamer (CICA- 

 DELLIDAE) ; these vectors all belong 

 to the subfamily Amhlycephalinae; all 

 tested species of this, but none of any 

 other, subfamily have proved capable 

 of transmitting this virus. Not by in- 

 oculation of expressed j uice . Not through 

 soil. 



Literature: Frazier, Phytopath., 3^, 

 1944, 1000-1001; Hewitt, Phytopath., 29, 

 1939, 10; SI, 1941, 862; Blue Anchor, 18, 

 1941, 16-21, 36; Hewitt et al., Phytopath., 

 32, 1942, 8; Houston et al., Phytopath., 

 32, 1942, 10; Milbrath, Calif. Dept. Agr., 

 20th Ann. Rept., Bull. 28, 1940, 571; 

 Pierce, U. S. Dept. of Agr., Div. of Veg. 

 Path., Bull. 2, 1892, 1-222; Weimer, 

 Phytopath., 21, 1931, 71-75; 27, 1937, 

 697-702; Jour. Agr. Res., 47, 1933, 351- 

 368; 53, 1936, 333-347; 55, 1937, 87-104. 



