55 

 Report of the Dodder Committee. 



BY 



Db. a. von DEGEN, 

 Director, Royal Hungarian Seed Control Station, Budapest. 



On the occasion of the Copenhagen Congress a Committee was appointed 

 to study the question of dodder. As members of this Committee were 

 elected Director Vitek, Professors Bussard and Voigt, Director Enesou 

 and myself, who are all representatives of European countries where the 

 cultivation of clover and alfalfa is of very great importance. The Congress 

 having decided that the Committee should choose its own Chairman, I 

 accepted this position in accordance with the wishes of my colleagues, and 

 I have since taken all those initial steps necessary for approaching the 

 solution of the main problem assigned for the Committee's investigation. 



This problem was to determine, at least approximately, and for the 

 present only for Europe, the bounds within which the dodder plant produces 

 its noxious effects, distinguishing, so far as possible, the scope of the so- 

 called large-seeded dodder and that of the common dodder. 



Experience had already taught los that certain parts of Europe — ^for 

 instance, the northern regions and such parts as are situated at a greater 

 height above the sea -level — are immune, or almost immune, against 

 dodder infection, since the plant, when introduced to these parts, fails to 

 become acclimatised and disappears after a brief period. 



On the other hand, we knew, also from experience, that there were 

 eertaih regions in Europe where acclimatisation of the dodder was indeed 

 possible, but was neither certain nor constant ; regions in which the plant 

 might or might not develop and produce ripe seed according as the weather, 

 during the period of vegetation, was warm and dry, or cool and wet; 

 therefore regions which, under certain circiitnstances, could become 

 infected, and would, at all events, be exposed to danger by the importa- 

 tion of seeds infected with dodder. 



It was clear from the outset that here the chmatic influences were of 

 primary effect. 



Even the use to which the red clover and alfalfa are appUed — whether 

 these plants are cultivated only for the pmpose of obtaining fodder 

 or also for the purpose of procuring seed— is of some importance in the 

 development of the dodder, in so far as in the case of plants cultivated 

 exclusively for the production of fodder, the more frequent mowing 

 unfavourably affects the development of the dodder and, indeed, often 

 renders seed formation impossible, while in districts where clover seeds are 

 also harvested, the clover plants have a longer period of rest during which 

 the dodder has also time for development. Still, the use to which the plante 

 are applied is also closely connected with climatic factors, for in the dis- 

 tricts which are warm and dry there is also invariably a harvest of clover 

 seeds, while, in cooler districts with a more abxmdant rainfall, the clover 

 serves only as a fodder crop. Thus the question here also is one of climatic 

 limits. 



Now, while the countries which only produce fodder are constantly 

 obliged to import seed, the seed -producing countries export from year to 

 year a certsiin quantity which is, to some extent, infected with dodder 



In addition to the influence exercised by the use to which the plants are 

 appHed, another influence on the propagation of dodder is found in the 

 conditions of cultivation in the different countries, notably in the more or 

 less strict adherence to the regulations designed to combat the evil. How- 

 ever, as these regulations are by ho means strictly enforced in Europe, we 

 may well leave them out of consideration. The methods of extirpation 

 involve great expense, and therefore the diflerent countries much prefer 

 to confine themselves to regulations for the prevention of the importation 



