U IOWA AGRICULTURAL COLLEGE. [H4 



As a troublesome parasite, Clover Dodder seems to have been observed in 

 Germany about the beginning of this century. Flux Dodder seems to have 

 been known lorn much longer period, as it is mentioned by writers as early 

 as L760. Flax Dodder occurs in this country, l>nt is not troublesome. In 

 Europe it does much damage. The South American ('use/da racemosa — 

 Martius var, Chiliana engelm — lias occasioned some trouble in European 

 -alfalfa. It has also been introduced with the svvi\ of this plant into Cali- 

 fornia, where it now injures the crop to sonic extent. 



Professor Macoun reports Clover Dodder in his catalogue of Canadian 

 plant.-, published in L884, a- occurring in Ontario, and introduced with 

 clover seed. It may possibly occur in other parts of the United State- and 

 that I have failed to see the reference. 



Fortunately all these pests are not so common in this country as to materi- 

 ally affect our crops. Whole clover fields are destroyed by the Clover Dod- 

 der in England and on the continent. Jt should, therefore, not be allowed 

 hi spread in this country. The existing patch should be exterminated imme- 

 diately. 



HOW To EXTERMINATE THE WEED. 



Several means suggest themselves. Cover the patch with straw and burn it 

 with the clover. A more radical way would be to use oilof vitriol and water 

 in the proportion of one of the oil of vitriol to three thousand of water; but 

 this must render the soil quite unfit for use at least for a year or two. If it 

 covers large areas clover ought to be followed by plants upon which dodder 

 will not grow. It has been found to grow with preference on leguminous 

 plants, showing its best development on clover vetch. The common bean is 

 seldom affected. At times it occurs on other leguminous plants, on various 

 weeds growing near clover patches, on some members of the carrot family 

 {Unbelliferae) and on common nettle (Urticaceae): it produces both dowers 

 and seeds. Haberlandt found that it would not even start on flax, sunflowers, 

 and hemp, but can be made to grow for a short time on mangolds, common 

 bean, and Indian corn. 



It will be well, therefore, to follow clover with oats, wheat, and barley, or 

 such other plants upon which it will not grow. Above all. we should pre- 

 vent its appearance. It must be remembered that dodder seed maintains 

 it- vitality !'<»r several years in tic soil, and that the seeds are distributed in 

 several way-, first, by animals; second, by sowing clover and the like con- 

 taining dodder seed. Animals eating clover containing dodder seed carry 

 it for some distance. It has been shown that after it has passed the alimcn- 

 taiy canal the seeds are still capable of germinating. In Europe sieves are 

 used to separate dodder from the clover seed, a- the latter is very much 

 smaller. It -rem- proper in this connection to say that suspected seed 

 should be senl t<> -(.me of the experiment stations, as many seeds have a 

 characteristic structure, and can easily be recognized by aid o\' the micro- 

 scop* 



-i excellent aeoounl <>f tin- parasite may be round in Sorauer, Diseases <»f 

 raukhetten) Vol. II. page 32. Also V <;. Smith, Diseases of Field and 

 n « !rops. 





