New York AGRICULTURAL EXPERIMENT STATION. 197 
the alfalfa is mostly killed out while around the margin the ground 
is covered with a tangled mat of yellow threads which twine closely 
about the stems of the alfalfa plants and slowly strangle them. The 
spots increase in size from year to year. Many alfalfa fields have 
been completely ruined by dodder, sometimes during the first season 
after sowing, but more commonly in the second or third season. 
In New York, it is not often injurious to other crops (except red 
clover), but once established in an alfalfa field it is very difficult | 
to eradicate without killing the alfalfa. 
Dodder produces clusters of small white flowers, also seeds (see 
Plate XVII), but is leafless and has no connection with the soil ex- 
cept during the seeding stage. It is a parasite, deriving all its 
nourishment from the host plant about which it twines. The dod- 
der infesting alfalfa in New York is probably of two or more kinds 
closely similar in appearance and producing similar effects. The 
kind of dodder most abundant in New York (Cuscuta epithymum) 
does not commonly seed here. It is carried over from one season 
to the next by means of the yellow threads which live over winter 
around the crowns of the plants (see page 203). Since trouble 
with dodder generally originates in the use of dodder-infested al- 
falfa seed it may be easily prevented by sowing only pure seed (see 
page 193). Frequent mowing will not kill dodder. It can not be 
combated successfully with sprays. Close pasturing is not prac- 
tical. Heavy mulching with coarse manure and the application of 
strong chemicals such as arsenite of soda, crude carbolic acid and 
common salt are methods having some merit. Digging over the 
spots is effective, but expensive and not practicable in stony soil. 
In most cases the most satisfactory method is to burn over the in- 
fested spots using kerosene and dry hay to insure a hot fire which 
will kill the alfalfa as well as the dodder. This applies where the 
spots are not very numerous. Badly infested fields should be 
plowed up. In New York plowing generally eradicates dodder 
promptly so that, usually, infested fields may be reseeded at once 
with safety. 
IMPORTANCE. 
In New York, dodder is a really serious alfalfa pest, but it is 
outranked in importance by weeds and by leaf spot (Pseudopeziza 
medicagimts). Also, certain uncongenial soil conditions such as 
acidity, wetness and deficiency in nodule-forming bacteria, are more 
important. The notoriety attained by dodder is largely due to the 
plant’s strange appearance which attracts attention to it. It is true, 
