208 REPORT OF THE DEPARTMENT OF BOTANY OF THE 
cult to determine whether it is best to plow up the field or to kill 
out the dodder by some other method. In reaching a decision in 
such cases it should be taken into consideration: That the eradica- 
tion of dodder is difficult; that the successful reseeding of infested 
spots is difficult; and that an alfalfa field when once established 
should last many years. When there are only a few dodder spots 
. scattered through the field they may be given local treatment and the 
plowing up of the field avoided. A dodder-infested field which has 
been plowed up may be planted afterward with any of the common 
farm crops, excepting, perhaps, alfalfa and clover, without any dan- 
ger of the reappearance of dodder. Dodder is readily subdued by 
plowing. How much danger there is in reseeding with alfalfa or 
with clover is uncertain. This subject is discussed more fully on a 
subsequent page. Much has been written about the eradication ot 
dodder, particularly in Germany, and numerous methods have been 
recommended :*!(1) The application of various chemicals, some in 
the form of spray to kill the dodder without destroying the alfalfa, 
others to kill both the parasite and its host. In the former method, 
the substances most frequently used are copper sulphate and iron 
sulphate; in the latter, sulphuric acid and common salt. (2) 
Smothering. Some advise covering the infested spots deeply with 
coarse manure to kill both dodder and alfalfa; others recommend 
light coverings of manure, finely cut straw, gypsum, etc., which are 
expected to smother the dodder while the alfalfa breaks through 
and continues its growth. (3) Close pasturing with sheep or cattle. 
(4) Close mowing. (5) Digging over the infested spots. (6) 
Burning over infested spots. 
Several of the above methods have been tried in alfalfa fields in 
this State with varying degrees of success. As yet, New York 
farmers have had too little experience with dodder to have any es- 
tablished methods of treating it. Our observations and experiments 
convince us that under New York conditions, the only really prac- 
ticable methods are those in which both the parasite and its host are 
killed. Attempts to preserve the life of infested plants invariably 
result in the escape of some of the dodder which necessitates re- 
peating the treatment again and again. This is the trouble with 
spraying. It is impossible to reach all of the dodder with the spray. 
Recommendations for close pasturing and close mowing are based 
on the false assumption that dodder may be eradicated by preventing 
“For the eradication of dodder see Sorauer (97, 2:47); Kthn (58); 
Kiessling (54); Hillman (46); Dawley (21). 
