818 
caution, it might be well to avoid pur- 
chasing seed from localities in which the 
disease is known to exist. Seed disinfec- 
tion might perhaps be practical, but this 
has not been demonstrated. Crown gall 
is a serious disease, and if it becomes gen- 
eral in the state, is likely to cause great 
loss. It is hoped that all growers will 
be on the lookout for the trouble and 
will use every effort to prevent it from 
spreading. Little is known of the disease 
as it occurs under American conditions. 
A thorough investigation of the trouble 
would be desirable. 
Dodder of Alfalfa and Clover 
H. 8. JACKSON 
Cuscuta sp. 
A trouble of alfalfa and clover common 
in the Northwest and somewhat different 
in nature from any of the diseases pre- 
viously discussed, is caused by a parasitic 
flowering plant known as dodder. The 
dodders are weeds which, as causing a 
disease of clover and alfalfa, are known 
to be common throughout the world, in- 
cluding nearly all sections of the United 
States where these crops are grown. 
Kinds of Dodder 
Contrary to the usual idea, dodder in 
clover and alfalfa is not caused by a 
single kind or species, but by several 
different species of dodder which may 
exist upon these hosts. *Hillman gives 
five species of dodder which are known 
to affect alfalfa and clover in the United 
States. Concerning these he offers the 
following information: 
“Clover dodder (Cuscuta epithymum, 
often referred to as Cuscuta trifolu) in- 
fests both the true clovers and alfalfa 
indiscriminately. It is widely distribut- 
ed in foreign countries and in the United 
States east of the Mississippi river and 
in the Northern Pacifie states. 
“Small-seeded alfalfa dodder (Cuscuta 
planifiora) as it occurs in this country 
appears to confine its attacks to alfalfa 
in preference to the true clovers. Thus 
far there is no evidence of any damage 
from this dodder to red, alsike, or white 
* Hillman. Dodder in Relation to Farm 
Seeds U. S. Department of Agriculture, Farm- 
ers Bulletin 306, 1907. 
ENCYCLOPEDIA OF PRACTICAL HORTICULTURE 
clovers. This is by far the most abund- 
ant and destructive of the dodders in 
the Western states. 
“Field dodder (Cuscuta arvensis, as 
recognized in the botanies) is widely dis- 
tributed throughout the United States. 
It infests both the clovers and alfalfa and 
also many wild herbaceous plants. It has 
proved injurious to sugar beets in Utah. 
“Large-seeded alfalfa dodder (Cuscuta 
indecora) is common in the West, espe- 
cially in Utah. It infests alfalfa as well 
as various wild plants, but it does not ap- 
pear to damage the true clovers. 
“Chilean dodder (Cuscuta racemosa 
chileana) is not generally known in this 
country. It is common in South Ameri- 
ca and has been reported from Europe. 
It is said to have flourished for a time 
in California many years ago, but sub- 
sequently disappeared. It is of interest 
because of its prevalence in alfalfa and 
red clover seed-producing regions of South 
America, from which seed is being sent 
to the United States, for this dodder in- 
fests both alfalfa and red clover. Little 
is known of this dodder in its relation 
to forage crops in this country, but since 
it is being brought here in considerable 
quantity from South America it is very 
likely that it will become one of the sev- 
eral injurious species established in the 
United States.” 
The three most common ones found in 
alfalfa seed in the Northwest are Cus- 
cuta planifiora, Cuscuta arvenis and 
Cuscuta indecora. Cuscuta arvenis is 
common upon clover as well and Cus- 
cuta epithymum is also common in this 
state, 
Appearance in Field 
Dodder may be recognized at a dis- 
tance by the yellow appearance of spots 
in the field. At close range this appear- 
ance will be found to be due to the abund- 
ance of the yellow thread-like dodder 
plants which twine about the stems of 
the alfalfa or clover. At first the dodder 
will be seen only in a small area, infect- 
ing one or two plants. It rapidly spreads 
in all directions by branching of the 
threads from these to other plants till 
large areas are covered. During this 
