236 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



and truck gardens. Demonstrations for the purpose of informing 

 farmers as to the best methods of controlling the pest were carried 

 on in many parts of the region. 



MOUNTAIN BEAVERS. 



The same general region is inhabited by an animal known as the 

 " mountain beaver " or " sewellel," which, until recently, has been of 

 little economic importance. Lately, however, these animals have ex- 

 tended their operations into cultivated areas and have destroyed 

 raspberry and blackberry bushes and also farm produce. Prelimi- 

 nary experiments for their control were conducted. 



PINE MICE, 



The pine mouse of the Eastern States, owing to the destruction of 

 its natural enemies, has greatly increased in numbers and not only 

 destroys seeds but feeds upon sweet potatoes and other tubers and 

 upon the roots of fruit and shade trees. Preliminary experiments 

 and demonstrations were made for the control of this rodent. 



CRAWFISH IN MISSISSIPPI. 



Demonstrations of methods for destroying crawfish, so injurious in 

 Houston clay lands of Mississippi and Alabama, were continued 

 during the year. The methods that have been worked out have 

 proven so successful that perfect stands of cotton were secured on 

 land that had previously been heavily infested and the crops de- 

 stroyed by these pests. It is estimated that after the first thorough 

 treatment lands can be kept free from crawfish at an annual ex- 

 penditure of not to exceed 25 cents per acre. 



MORTALITY AMONG WILD DUCKS IN UTAH. 



For several successive years large numbers of wild ducks and 

 other waterfowl aroimd Great Salt Lake, Utah, have died, apparently 

 from some disease, the exact cause, however, being unknown. As the 

 destruction of waterfowl amounts annually to many thousands, the 

 pecuniary loss is very great. During the summer of 1914 an assist- 

 ant of the bureau carried on field investigations in the Salt Lake 

 Valley, continuing until the end of October. Undoubtedly all the 

 species of ducks that habitually feed in shallow water are more or 

 less affected, but during the summer's work only nine affected species 

 came under observation. The loss among them was very great. In 

 1912 nearly 45,000 dead ducks were picked up on one marsh. 



It is of interest to note that the fatality is by no means confined to 

 ducks, but includes many species belonging to widely different fam- 

 ilies, as grebes, herons, shorebirds, avocets, and stilts. The trouble 

 during the present year began in July and terminated about Sep- 

 tember 20. The birds affected seem partially paralyzed, losing the 

 power of flight, and gradually weakening until they die. The first 

 clue to the nature of the trouble was obtained when it was found 

 that affected ducks generally recover readily when given fresh water, 

 and of 586 so treated in experimental pens 426 were entirely cured. 



