DISEASES OF ALFALFA 365 



jury; cutting the crop when they appear forces them to 

 migrate. Such rodents as prairie dogs and meadow mice 

 are destructive to stands of alfalfa in the West. These can 

 best be dealt with by poisoning with grain or potatoes soaked 

 in strychnine, or pouring carbon bisulphide into the burrows. 



482. Diseases. Various rusts, leaf-spots, and mildews 

 sometimes attack alfalfa, particularly when it is growing 

 under unfavorable circumstances. About the only remedy 

 is to mow the field, removing the diseased stems and leaves 

 and encouraging the development of strong new growth. 

 In Texas, a disease known as root rot is destructive to this 

 and other taprooted plants. This can best be kept in check 

 by growing grain or corn on the land for several years, as 

 these plants are not affected. 



483. Weeds. Numerous weeds make the growing of 

 alfalfa rather difficult; wild barley, crabgrass, and foxtail are 

 particularly troublesome. In the blue grass region, Ken- 

 tucky blue grass is one of the worst pests with which the 

 alfalfa grower has to contend. All these plants can be kept 

 down to some extent by disking, but when they once gain a 

 foothold, it is often better to break up the alfalfa sod and 

 cultivate the land for two years before starting anew. Where 

 these grasses are common, a short rotation is better than 

 leaving the land in alfalfa for many years. 



Alfalfa dodder, a parasitic vine, is as serious a pest as 

 dodder in clover. The same remedies, the sowing of clean 

 seed and the removal of all dodder plants wherever they ap- 

 pear, are appUcable. 



LABORATORY AND FIELD EXERCISES 



A study of the growth of alfalfa, its root system, and the tubercles 

 on its roots, may be made in the field, if the crop is grown in the neigh- 

 borhood. At least a small plat of this plant should be grown on the 

 school farm. Some time may well be spent in the study of alfalfa 

 seed, to become familiar with the seed and to aid in detecting adulter- 

 ants and other impurities, 



