DISEASES AND INSECT INJURIES. 147 



crop is in full bearing is very large, from 25 to SO tons 

 being readily obtained, where attention has been paid to 

 the cultivation and the plants kept clean and well 

 manured. There are a great number of reports recorded 

 in some of the older works on agriculture as to number 

 of horses and of other stock ke.pt upon the produce of a 

 given area under this crop, and also of its value as a food 

 substance for milking cows. We can readily form our 

 own estimate on these points when we know its organic 

 composition, and the weight per acre of the produce ; we 

 then can judge pretty correctly as to its real feeding value 

 and what amount of v stock it ought to keep. 



Lucerne seems to be less affected by disease than the 

 clovers. It is a far more delicate plant, and therefore will 

 not grow successfully in the same climates. The peculiar 

 disease which, in our ignorance of its causes, we term " clover 

 sickness" has not been noticed; while, owing to the great 

 depth to which the roots of the lucerne penetrate, it rarely 

 suffers from drought and its consequent form of disease, 

 "mildew," which tells so severely at times on the clover 

 crop. Indeed, when lucerne is well rooted in the soil, it 

 looks fresh and green, even during the hottest weather, 

 when all around is parched and suffering. 



The insect injuries to which it is subject resemble those 

 described in regard to the clover crop. Slugs and snails 

 are its chief enemies during the early stages of growth, 

 the remedies for which have already been described. The 

 common turnip-fly is also said, by Arthur Young, and 

 others, to be very destructive to the young plant ; to avoid 

 which it has been recommended to set the seed in at the 

 beginning of April, before the insect is about our fields. 

 The same caterpillars which attack the clover are equally 

 injurious to the lucerne, which also suffers from a beetle 

 the Colas-pis atra which, both in its perfect and the 

 larva state, eats off the young leaves as they grow, the 



