198 REPORT OF THE DEPARTMENT OF BOTANY OF THE 
however, that many farmers have had more or less trouble with 
dodder. Some fields have been ruined by it the first season, but in 
the majority of cases the greater part of the damage is done during 
the second and third seasons after sowing. Sometimes it is quite 
destructive in the second season where it was not observed at all 
during the first season. It is most conspicuous in the second and 
third cuttings. 
Although dodder-infested hay is not refused by cattle it appears 
that they do not entirely relish it. There is no evidence that dod- 
der is in any way injurious to cattle or other animals. 
APPEARANCE OF INFESTED FIELDS. 
The alfalfa is killed out in spots which vary much in size and 
shape. Spots resulting from a single infection are generally cir- 
cular and rarely attain a diameter of more than 5 or 6 feet during 
the first season. Usually, they increase in size from year to year, 
ultimately reaching a diameter of 30 feet or more. In some spots 
the dodder dies out and may be said to have become extinct. By 
the coalescence of two or more spots large bare areas of irregular 
shape are formed. On the interior of the spots there remain a few 
scattered alfalfa plants which, somehow, escaped destruction by the 
dodder, but the ground is occupied chiefly by weeds. 
Dodder-infested spots are especially conspicuous during the first 
week in May, owing to the fact that the alfalfa starts into growth 
sooner than the weeds on the interior of the spots. The dodder, 
however, is but little in evidence at this time. Its presence is re- 
vealed only by careful search. Later (from about June Io on) 
it becomes conspicuous as a tangled mass of yellow threads which 
twine closely about the alfalfa plants around the margin of the spot. 
Not infrequently the dodder mats are so dense that they impede the 
progress of the mowing machine. Little or no dodder is found in 
the interior of the spots,—only around the margins. 
SPECIES AND HOST PLANTS. 
According to Engler and Prantl*® there are go species of Cus- 
cuta, the genus to which the dodders belong. All are parasites, but 
only a few of them are injurious to alfalfa. Just how many species 
of Cuscuta may attack alfalfa it is difficult to say. Hillman*! gives 
“Engler u. Prantl (28). 
“Hillman (46). 
