BUEEAU OF PLANT INDUSTRY. 53 



port the view that it is due to insufficient moisture in the subsoil at 

 some time during the growing season. A brief report on the trouble 

 was made, in which the main conclusions reached were given, together 

 with recommendations which it is believed will lead to the overcoming 

 of the blight and be of material advantage to the industry. The fact 

 that the blight has disappeared with the past winter's normal rainfall 

 is in harmony with the above conclusions. So far as may be necessarj^ 

 the study of the disease will be continued. 



Miscellaneous. — Considerable data relative to black canker of the 

 apple in Oregon and Washington have been collected, and if sufficient 

 assistance can be provided and time permits, an extensive series of 

 spraying tests to control the disease will be undertaken the coming 

 season. In addition to the canker, a large number of minor diseases 

 have been studied during the year, among them being a bacterial 

 disease of loquats, which, as before mentioned, is perhaps pear blight. 

 Besides the scientific work conducted at the Pacific coast laboratorv, 

 a large correspondence is carried on, and through this channel the 

 influence of the work is materially extended, 



W^ORK IN THE MISSISSIPPI VALLEY. 



This work has so increased that it has been found desirable to estab- 

 lish at St. Louis what is known as the Mississippi Valley laboratory. 

 Through the cooperation of the Shaw School of Botany and the Mis- 

 souri Botanical Garden our work at this laboratory is greatly facilitated. 

 The assistant in charge is vigorously prosecuting work on the special 

 problems liertaining to the Mississippi Valley and also on diseases of 

 forest trees and construction timber and the root rot of fruit trees. 

 During the early part of the past year he made an extensive trip 

 through California and the West studying the diseases of trees, col- 

 lected and prei^ared for the Pan-American Exposition one of the finest 

 exhibits of specimens of diseased wood ever made. He also prepared 

 and published two bulletins and a Yearbook iiaper on diseases of trees, 

 and inaugurated some extensive experiments in Missouri and Illinois 

 for the purpose of working out a remedy for root rot and bitter rot. 

 (See "Diseases of fruit" and "Root rot of fruit and other trees.") 



WORK AT THE TROPICAL LABORATORY. 



The large amount of information which we are called upon to sup- 

 pl}^ relative to diseases and culture of tropical crops has made it nec- 

 essary to establish the tropical laboratory in connection with the 

 tropical garden maintained at Miami, as set forth in previous reports. 

 An expert pathologist has been placed in charge of this laboratory, 

 and the work is being pushed vigorously. Many new introductions 

 have been set out in the garden during the year, and are being tested 

 to determine their freedom from injurious diseases and for the jiur- 

 pose of propagating them for distribution to the State experiment 

 stations and to others in the regions to which they are adapted. The 

 hybrids being tested here will be discussed further under "Plant 

 breeding." In addition to the work now being carried on, the labora- 

 torj' will take up the study of diseases of truck crops for Northern 

 markets, and will resume, the work on citrous and other subtropical 

 fruits, which was dropped on account of the destruction of such trees 

 by the great freezes a few years ago. 



