PLANT PATHOLOGY 



J. G. Brown 



Recent agricultural developments within the State have 

 emphasized the economic importance of plant diseases and have 

 correspondingly increased the demands made on the Agricul- 

 tural Experiment Station. Formerly, requests for assistance 

 in combating diseases of plants M^ere referred to the Station 

 Botanist, but in time the volume of work became so large that 

 it was necessary to establish a Department of Plant Pathology, 

 which was done July 1, 1920. Since the annual budget had al- 

 ready been prepared and adopted, the work of the new depart- 

 ment has been somewhat handicapped by the lack of funds for 

 purchasing needed instruments and apparatus. 



WORK OF THE DEPARTMENT 



The most pressing plant-disease problems have been taken 

 up in the form of projects; miscellaneous studies of infected 

 plants which have been sent in from various agricultural dis- 

 tricts of the State have been made; information has been pub- 

 lished from time to time in the forni of leaflets dealing with 

 diseases prevalent in the State and describing the latest methods 

 for controlling these diseases; a plant survey of the State has 

 been carried on in cooperation with the Federal Plant Disease 

 Survey. 



DATE ROT 



An important disease known as date rot confronts the 

 Arizona date grower. This rot is so extensive during unfavor- 

 able years that as high as 95 percent of the crop is damaged. 

 Processing the fruits saves a part of the crop if it is treated 

 in time, though the quality is impaired by the disease. Usually 

 before ripening has sufficiently progressed to warrant harvest- 

 ing, a large part of the crop falls to the ground. 



Date rot is characterized by two main symptoms: very 

 small chocolate-brown spots appear on the fruit, finally coalesce, 

 And eventually cover one side. In other cases minute spots 

 having a watersoaked appearance, form, gradually enlarge, and 

 finally unite to make a blister. In the development of both 

 kinds of spots the protective layers of the fruit become rup- 

 tured, resulting in drying and mummification. The mummi- 

 iied fruit may remain hanging to the clusters or it may fall to 



