592 FORAGE PLANTS AND THEIR CULTURE 



Craig states that an acre of good rape will carry 30 hogs 

 for 2 months. 



709. Yields. Yields of rape range from 5 to 30 tons 

 an acre green weight. The average yield on the experi- 

 mental plots at Guelph, Ontario, for 6 years was 20.1 

 tons and the maximum 27.7 tons. Yields to the acre 

 reported from other experiment stations are : New Hamp- 

 shire, 50 tons ; Wyoming, 14.6 tons ; North Dakota, 5.5, 

 6.5, 14 and 5.2 tons for four years in succession ; Florida, 

 16.59 tons; Michigan, 6.46 tons. 



The average yield of a good field of rape is probably 

 about 10 tons an acre. 



710. Insects. Rape, like all plants of the cabbage 

 tribe, is much subject to the attacks of numerous insects, 

 and this factor tends to restrict its culture as a field crop 

 to regions where the growing season is cool. The most 

 troublesome insects are the Cabbage Aphis (Aphis bras- 

 sicce), a small plant louse which often swarms on the 

 plants in enormous numbers ; the Cabbage-worm (Pieris 

 rapce), a smooth, green caterpillar that feeds on the leaves ; 

 the Harlequin Plant-bug (Murgantia histrionica) , a hand- 

 some insect which sometimes attacks the leaves in enor- 

 mous numbers and the Root-maggot (Anthomyia brassicce), 

 a small white grub which feeds on the roots near the sur- 

 face. 



KALE (Brassica oleracea) 



711. The -varieties of kale used for forage are the coarse- 

 growing sorts, especially the one known as Thousand- 

 headed. This is much grown in England and France as 

 a soiling crop, and has been found admirably adapted to 

 the north Pacific Coast, in Ontario, and in New England. 

 The plants grow to a height of 3 to 5 feet or more and pro- 

 duce larger yields of succulent forage, which can be fed 



