158 ANNUAL EEPOETS OF DEPARTMENT OF AGEICULTTJEE. 



MARKETS INSPECTION WORK. 



During the latter half of the fiscal year this bureau cooperated with 

 ' the Bureau of Markets in the inspection of carload lots of perish- 

 able vegetables at terminal markets, to determine the cause of dete- 

 rioration in food products and to seek means of preventing such 

 losses. Pathologists visit the headquarters of the Markets Inspec- 

 tion Service and work with the inspectors, teaching them how to 

 identify vegetable diseases and at the same time tracing diseased 

 shipments to their origin, where the problems of introducing con- 

 trol measures in the field are taken up by the extension pathologists. 

 An important feature of this work is the preparation of a handbook 

 of vegetable diseases for the guidance of the inspectors. 



In the short time since the beginning of this work much has been 

 accomplished in the way of familiarizing the inspectors witli the 

 diseases of vegetables and the following up of cases of severe losses, 

 such as black-heart in potatoes from the North-Central States and 

 powdery dry-rot in potatoes from the Gkreat Plains and Eocky Moun- 

 tain States. Studies of pathological problems involved in tlie trans- 

 portation and handling of fruits have also been undertaken in coop- 

 eration with the Bureau of Markets. 



BLACK-CHAFF OF WHEAT. 



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Studies have continued on the biology of the organism causing the 

 black-chaff of wheat, and numerous field observations have been 

 made on its distribution. It occurred this year in many places in 

 Iowa, Kansas, Nebraska, and the neighboring States. It has not 

 been discovered east of Illinois. 



Work is also in progress upon methods of prevention. Th^e or- 

 ganism has been found to be quite sensitive to copper sulphate, and 

 inasmuch as it is usually carried on the seed from one field to an- 

 other it is thought that a seed treatment can be devised for holding 

 it in check. 



WILT OF THE CASTOR BEAN. 



A disease of castor-bean plants has developed in Georgia and 

 Florida, and studies of this have shown it to be due to the same or- 

 ganism as that causing the wilt of tobacco and other solanaceous 

 plants. Castor beans, therefore, should not be planted on land 

 knowm to be subject to the bacterial wdlt of tobacco, potato, tomato, 

 eggplant, or peppers. 



PLANT PHYSIOLOGICAL INVESTIGATIONS. 



INORGANIC REQUIREMENTS OF CROP PLANTS. 



Work on the relation of calcium salts to the physiological avail- 

 ability of the mineral soil constituents has been continued, with re- 

 sults in harmony with those reported last year. The practical im- 

 portance of a sufficient supply of some source of calcium, whether 

 in the form of limestone, lime, or gypsum, in order to secure the 

 value present in the other chemical soil constituents, is emphasized. 



In view of the present interest in the potash supply, some attention 

 was given to a study of the availability of the greensand deposits 

 occurring in the Eastern States from Sandy Hook, N. J., to southern 



