VEGETABLE AND FIELD CROPS 215 



seed bed, and special care should be taken to avoid infecting 

 the seed bed with soil, manure, or refuse. Air-slaked stone 

 lime, 75 bushels per acre, applied each year some weeks be- 

 fore planting, has given beneficial results. In New York, 

 where 90 bushels of shell lime were applied per acre, an ex- 

 cellenl crop was grown, while upon untreated soil only 60 

 heads were cut from 472 plants.' 



Club root occurs upon cabbage, kale, cauliflower, turnip, 

 rutabaga, collards, Brussels sprouts, radish, stocks, candy- 

 tuft, sweet alyssum, and upon wild cruciferous plants, 

 shepherd's purse, peppergrass, pennycress, black mustard, 

 charlock, false flax, hedge mustard. 



Altemariose (Alternaria Brassicoe (Berk.) Sacc). — - 

 This disease is described under collard. Upon the cab- 

 bage, particularly in the South, it is quite destructive^ 

 both in the field and in storage. .. , 



Sclerotiniose (Sderotinia tiibh-tiana Fckl.). — This mal- 

 ady is thoroughly discussed under lettuce. Upon the 

 cabbage it may be recognized by the cotton-like myce- 

 lium and the black sclerotia which appear in advaaced 

 stages of disease. ', 



A form of this rot is described by Hedgcock^ as closely 

 resembling black rot, except that it is more watery. Often, 

 too, the petioles rot away at the base and the leaves droop. 

 Sclerotia are often found. 



Downy mildew (Peronospora parasitica (Pers.) DeBy.). 

 — The downy mildew produces the characteristic downy 

 patches of sporophores upon the lower surface of the 

 leaves, much as is the case of the grape. Seen from above 



' N.Y. (Geneva) Agr. Exp. Sta. Rpt. 14, p. 528. 



' Hedgcoek, G. G., Mo. Bot. Gard. Rpt. 16, p. 149, 1905. 



