12 H. H. Whetzel and John M. Arthur 



to another. Klebahn (1907:28-29), who gave considerable attention to 

 this matter, concludes that the fungus probably is not often carried on 

 tulip bulbs since infected bulbs are so severely rotted that they would 

 seldom appear in the market. Moreover, he observed that affected bulbs 

 rarely produce bulbils. Both Klebahn and Ritzema Bos suggest that 

 the fungus may be transported in diseased hyacinths or on bulbs of other 

 plants which suffer slightly with the disease. Both Muller-Thurgau 

 (1908:750) and Lendner (1911) cite cases of the occurrence of the disease 

 in Switzerland, in which the pathogene was undoubtedly brought in with 

 diseased bulbs imported from Holland. Lendner observed furthermore 

 that the newly formed bulbils also were; attacked. The authors' con- 

 clusion on this point, based upon the outbreak of the disease at Yonkers. 

 is that there, at least, all the evidence points to the introduction of the 

 pathogene on the tulip bulbs which were imported from Holland. No 

 other kind of bulbs had been recently planted in these beds. It is indeed 

 probable that the pathogene is only occasionally transported with bulbs 

 in the trade, and this may account for its apparently restricted occurrence. 

 Were it a pathogene commonly transported on tulip bulbs, it would long 

 ago have appeared in America with sufficient frequency and severity to 

 have attracted attention. 



The pathogene is a soil-con laminating fungus maintained from year 

 to year by its sclerotia. It appears to spread but slowly year after year 

 from a given center of contamination in the bed, and then only when tulips 

 are planted continuously in the same soil. That it may be disseminated 

 over a plot of ground through spading and cultivation is evident. 



The ease with which the sclerotia become separated from the diseased 

 bulbs, their formation in the soil about the bulbs, and the rotting-away 

 of the bulbs before the beds can be reworked and the diseased plants 

 removed, makes sanitary measures such as the removal of diseased bulbs 

 and surrounding soil to appear of little practical value. This seem-. 

 however, to be the method generally in vogue among Dutch bulb-growers, 

 who employ for this purpose a special tool (figure 4) known as the Tulpen- 

 stecker (tulip sticker). 



Ilotation where practical is recommended by Klebahn (1907:31), who 

 holds, however, that at least three years must elapse before tulips may 

 safely be returned to soil that has been infested. Moreover, other sus 

 ceptible bulbs may not be grown therein dining the interval (page 2(i 

 of same reference). 



Ritzema Bos (1903 a: 198^202 [p. 350-351 Ztschr.]) tested a number of soil 

 disinfectants for the control of the disease, among these being lime, sulfur, 

 and carbolineum. Of these, only the last proved to be fairly efficient, 

 although a considerable reduction in diseased bulbs was obtained by rolling 

 the bulbs in sulfur after wetting them with a 10-per-cent glycerine solution, 

 together with a liberal use of sulfur placed around the; bulbs when planting. 



