CLOVER AND ALFALFA DISEASES 
spreading, the plant first infested will 
gradually be killed by the parasite. The 
dodder dies with it, but continues to grow 
along the edges of the spot, so that, in 
the late season, dead spots surrounded by 
a circle of dodder infested plants may be 
observed in alfalfa or clover fields. The 
dodder in the meantime has blossomed 
profusely and ripened its seed. 
Dodder in General 
The dodders, or love-vines, are para- 
sitic flowering plants closely related to 
the morning glories, or bind weeds. 
There are several species occurring in 
this state besides those species which at- 
tack alfalfa and clover. Most of these 
grow on weeds, particularly in moist bot- 
tom lands, and do no damage to the 
farmers’ crops. 
These plants are peculiar in that they 
are parasitic in habit, depending on the 
plants upon which they grow for their 
food, instead of elaborating it for them- 
selves from the soil moisture and air as 
plants possessing green color are able 
to do. Dodders are destitute of this 
green color called chlorophyll and so have 
not the power of elaborating food for 
themselves. The plant consists of a yel- 
low stem which is practically leafless. 
The leaves have been reduced to very 
small scales. The flowers are minute and 
are usually produced in clusters on the 
stem. 
Life History 
During the first stages of growth the 
young dodder plant is self supporting, but 
is wholly dependent on the food stored in 
the seed. The seed, when it first ger- 
minates, consists solely of a yellow 
thread-like stem. The plantlet may or 
may not attach itself to the ground. It 
grows independently until the food in the 
seed is used up. During this time the 
thread-like stem has grown sufficiently to 
grasp and twine about some green plant 
growing near by. If this green plant is 
not one upon which the particular species 
of dodder naturally grows, it dies. If 
the plant is one for which the dodder has 
a natural affinity, it twines about the 
stem and sends suckers or haustoria into 
the tissue, thus linking the two plants 
819 
together. The haustoria serve both as 
holdfasts for the dodder’s support and as 
feeding organs through which the dodder 
takes the juices of the host, depriving it 
of needful food which it has manufac- 
tured for its own use. 
Propagation and Dissemination 
Dodder is most commonly distributed 
by the seed being mixed with the seed of 
the host plant. The various species of 
dodder are common in the districts where 
alfalfa and clover seed are grown and 
the seed of both host and parasite are 
matured about the same time, consequent- 
ly when an infested crop of clover or 
alfalfa is harvested, the seed is usually 
found contaminated with a certain per- 
centage of the dodder seed. In this way 
the disease is disseminated far and wide. 
The mixed seeds germinate when plant- 
ed, whereupon the dodder soon attaches 
itself to the clover and alfalfa, and after 
becoming permanently established on one 
plant may be spread from plant to plant 
in the field, slowly infesting considerable 
areas. 
When dodder is established in the field 
it may be disseminated by seed to other 
parts of the field during mowing and rak- 
ing. The dodder plant may remain alive 
for several days on the host plant after 
it has been cut, and if such diseased 
plants or parts of plants are scattered to 
other parts of the field the dodder may 
obtain a foothold on new plants and thus 
start other spots. It is shown that in 
New York dodder (Cuscuta epithymum) 
may live over winter on the crowns of 
infested plants. The seed of the small- 
seeded dodder which is so common in the 
West, may be spread by irrigation water. 
Preventive Measures 
Since dodder is disseminated almost ex- 
clusively through the seed, the most ob- 
vious method of preventing the introduc- 
tion of this trouble is by planting clean 
seed, that is, seed which has no dodder 
mixed with it. Certain species of dodder 
infesting alfalfa may be entirely removed 
by proper screening. The large-seeded 
species of dodder cannot be entirely re- 
moved by any process of screening known 
