DODDER 
The term dodder is applied as a common name to the pathogenes as 
well as to the diseases which they cause. It is used for all the diseases 
caused by species of phanerogamous parasites of the genus Cuscuta. 
The different dodder diseases are often distinguished by adding the host- 
name as, alfalfa dodder, clover dodder and the like. The pathologic 
effects are in all cases similar. 
SYMPTOMS 
All parts of the host above ground, especially the stems, are directly 
attacked by dodder pathogenes. The most striking sign is the dodder 
parasite itself. The tangled yellow stems matted about its host form 
conspicuous yellow patches in the field. These doddered areas, often 
several feet in diameter, are at first more or less circular. Examine the 
photographs showing spots in the field. oBSERVE:— 
. 1. The dwarfed and dying host-plants at the center of the dod- 
dered area. 
2. The densely matted dodder stems. 
3. The long spreading runner-like dodder stems about the 
margins of the area, extending out among the healthy plants. 
Examine the specimens provided and oBSERVE :— 
4. The yellow dodder vine entwined about the host-stems; 
size, color, shape in cross-section, branching. 
5. Evidences of injury to the host, to be detected by comparison 
-of diseased and healthy plants; dwarfing and chlorosis. 
Make a DRAWING to show the general appearance of a dodder-affected 
plant. : 
ETIOLOGY 
Dodder diseases are caused by-species of Cuscuta, a genus of the family 
Convolvulaceae. Some near relatives in the same familv are the morning- 
glories, bindweeds, buckwheat and sweet potatoes. There are about 
ninety species.of Cuscuta, of which about half occur in America. The 
most common one on cultivated crops like clover and alfalfa is Cuscuta 
epithymum Murray, a species introduced from Europe. 
Life-history. This pathogene has an annual life-history. It is known, 
however, that it commonly overwinters in a vegetative condition on 
perennial hosts like clover and alfalfa. (See N.Y. (Geneva) Bul. 305:369- 
374. 
Ca Primary Cycles are initiated by the seeds which have lain on 
the ground over winter. 
Pathogenesis. Examine seed of C. epithymum. NOTE:>— 
6. Their surface markings; color; and that the one side is 
convex while the other is flattened in two or more places. Measure 
several. DRAw:—(a) several to show variations in size and form; (b) two 
seeds greatly enlarged showing all their characteristics. Describe the 
color in the notes on the margin of the paper. 
7. Examine the seed of the other species provided. These 
mav all occur on clover or alfalfa. Make enlarged prawines of each 
so that they will be comparable in size with those of the drawings of C. 
epithymum. 
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