140 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



formaldehyde, provided this is done within 24 hours after digging. 

 Further surveys have indicated that the powdery scab disease is 

 confined to six sections of the United States, all of these being north- 

 ern except one locality in Florida. In every case these areas are in 

 sections with considerable rainfall, where soil conditions are such 

 that poor drainage prevails. It has been found that the disease can 

 be lessened by the application of seed and soil treatments. The cause 

 of potato " leak,"' a rapid type of decay causing serious loss in the 

 delta district of California, has been discovered, and experiments 

 have shown that it can be controlled to a marked extent by careful 

 harvesting and sorting before shipment. 



Foot-rot or sweet potato. — Foot-rot of the sweet potato has been 

 found to be a serious and destructive disease in several States. Suc- 

 cessful methods for its control have been discovered and demon- 

 strated, and studies of the resistance of varieties to the disease and of 

 its relations to storage rots are being made. 



Cotton diseases. — With the cooperation of the States Eelations 

 Service, work on the control of wilt, root-knot, and anthracnose of 

 cotton, forage crops, and truck crops in the South has been consider- 

 ably increased. Last season 1,545 acres of wilt-resistant cotton were 

 planted by cooperative breeders and growers in South Carolina 

 and 5,030 bushels of selected seed produced for sale to farmers. In 

 Alabama, where the work was begun only last year, 170 bushels of 

 selected seed were produced. 



Watermelon rot. — During the past two years a constantly increas- 

 ing number of reports of serious losses due to the deterioration of 

 watermelons in transit to northern markets have been received. The 

 investigation of these troubles was begun a year ago, and it has been 

 determined that at least 90 per cent of the loss reported was due to a 

 stem-end decay caused by a species of Diplodia. Field experiments 

 to control this fungus are yielding promising results. 



Oat blast. — A cooperative experiment with the Bureau of Ento- 

 mology has been initiated at La Fayette, Ind., to determine the cause 

 or causes of the infection commonly known there as oat blast. 



Wheat rust. — Many data have been obtained during the year on 

 the subject of rust resistance of both wheat and oats and on rust- 

 resistant wheat hybrids. Studies conducted in cooperation with the 

 Minnesota Experiment Station have revealed important relations 

 between the rusts of certain wild grasses and those of cultivated ce- 

 reals. Additional information has also been obtained on the distri- 

 bution of the new stripe rust disease. 



Wheat smut. — A device has been originated which promises a more 

 satisfactory and practical application of the hot-water treatment for 

 the prevention of loose smut of wheat and barley. 



Crown-gall. — Extensive researches upon the development of crown 

 galls upon plants show that these galls, which are caused by a bacil- 

 lus, have very many points of resemblance to human cancer. 



Damping-off of conifers. — Experiments in many widely separated 

 localities, as well as the cooperative experiments of the Forest Service 

 on a commercial scale, confirm our earlier report on the efficiency of 



