138 ANNUAL REPORTS OF DEPARTMENT OF AGRICULTURE. 



WHITE-PINE BLISTER RUST. 



Field studies of the white-pine blister rust indicate that, as might 

 be expected, the disease is more virulent in America than in Europe 

 and is taking on some new characters. 



A systematic survey, tracing nursery shipments of suspected white 

 pine and currants and gooseberries, has been conducted in all States 

 of the Union except Mississippi, Alabama, and Florida. Hundreds 

 of shipments from, diseased nurseries or from dangerous localities 

 have been located; these will require annual inspection. Diseased 

 stock has been located at one place in Arizona, one in Iowa, one in 

 South Dakota, one in Michigan, three in Wisconsin, one in Ohio, 

 three in Pennsylvania, and seven in New Jersey. All of this mate- 

 rial has been destroyed. 



Natural infections of blister rust have been found on the woody 

 stems of wild gooseberry, and similar infections have been produced 

 by inoculation. These results establish an overwhelming presump- 

 tion that the blister rust can be carried on the wood of cultivated 

 gooseberries and other members of the genus Ribes in nursery ship- 

 ments. They also go far to confirm the suspicion that the disease 

 occasionally overwinters on these plants. 



A method of diagnosing dubious or undeveloped cases of the white- 

 pine blister rust from the characters of the mycelium in the bark has 

 been devised. 



PLANT PHYSIOLOGICAL INVESTIGATIONS. 



PHYSIOLOGY OF " TOBACCO-SICK " SOILS. 



In the Connecticut Valley the leading feature of the work has 

 been a study of " tobacco-sick " soils, which are causing heavy losses 

 to growers, particularly under the artificial shades used for growing 

 wrapper leaf. Selected strains of Cuban and of binder types grown 

 on these soils have given very encouraging results, indicating that 

 the disease may be controlled by the growing of resistant varieties. 

 It has also been shown that the use of fertilizers of acid reaction 

 will materially reduce the injury caused by the disease. Finally, crop 

 rotation, wherever practicable, appears to be an effective remedy. 

 A similar or identical disease is giving much trouble in Maryland; 

 and while native varieties are susceptible, these have been crossed 

 with foreign resistant varieties, with a view to obtaining resistant 

 types adapted to local requirements. 



In Wisconsin and in the Burley section of Kentucky considerable 

 progress has been made in the control of tobacco root-rot through 

 the development of resistant varieties. The disease causes heavy 

 damage in these regions every year and ordinary Burley is espe- 

 cially susceptible. On fields on which the native Burleys have failed 

 completely, some of the resistant strains have given surprisingly 

 good results. 



INCREASING THE PRODUCTION OF DATE OFFSHOOTS. 



During the past year important investigations have been under 

 way in connection with the life-history study of the date palm. The 



