35 



can be entirely eliminated by applying the same methods as described 

 under drop of lettuce. 



Eel Worms. 



These are very likely to infect cucumber roots, and if very 

 abundant they greatly injure the crop. Many of our greenhouse 

 growers have been more or less troubled with them for some years. 

 For remedy see "Tomatoes." Cucumbers are occasionally subject 

 to other fungous diseases. The most important ones, however, 

 have been touched upon. 



Lettuce. 



There are various diseases common to greenhouse lettuce which 

 have been described in Bulletin No. 69, issued by the Hatch Ex- 

 periment Station, Amherst, Mass. 



Drop (Sderotinia Libertiana, Fckl.). 

 This constitutes the most destructive disease of lettuce, and is 

 characterized by the plants wilting and dropping into an insignifi- 



FiG. 6. — A typical normal lettuce 

 head. 



Fig. 7. — Lettuce plant affected with 

 drop caused by the fungus Sclerotinia 

 Libertiana. 



cant mass (see Figs. 6 and 7) . This troublesome disease is caused 

 by a sporeless soil fungus, which attacks the stem of the plant, 

 and the only efifectiial remedy is found in soil sterilization. 



Rhizoctonia. 

 This is the generic name of the fungus which causes a rotting 

 of the lower leaves of lettuce plants, and occasionally works in 

 the stem and head, much to the detriment of the crop. The fungus 

 is a sterile or sporeless type of soil organism, and the same remedy 

 is applicable to this as to the preceding trouble. 



Doivny Mildew (Bremia Latucoi, Kegel.). 

 A whitish, downy, mildew growth frequently grows on the lower 

 leaves of young lettuce plants, and on the exterior leaves of the 

 mature head. It seldom attacks the normal healthy portions of the 



