A Study of Meadow-Crop Diseases in New York 



113 



and stunted, indicating strong toxic effects. In figure 28 a spore germi- 

 nating in the presence of 7.2- per- cent copper- lime dust is shown. This 

 spore seems to be typical of the effect of copper. Most of the spores that 

 germinated in this dust produced the three- branched germ tubes from the 



Figure 28. germinating conidia of helminthosporium 

 vagans, showing the toxic effect of copper-lime dust 



a, Germination in distilled water; 6, in copper-lime dust 



terminal cells and almost never from any of the central segments. The 

 sketch of spore germination in distilled water may well represent the 

 germination in sulfur dusts. 



These tests indicate that commercial copper-lime dust applied under 

 moist conditions will probably control the disease satisfactorily by pre- 

 venting spore germination and penetration, and that any sulfur treatment 

 is likely to be ineffective in the field. 



