Arizona Agricultural Experiment Station 



607 



the ground. During the progress of the disease the browr^ 

 spots take on a light cream color in the center. Both kinds of 

 spots occur on the leaflets, and the brown spots are found on 

 leaf petioles and the stalks and branches of flower and fruit 

 clusters, but blistering does not occur on these more woody 

 organs. 



Fig. 6— Effects of date rot disease; note mummies still hanfenng to tree and on ground. 



Laboratory cultures of tissues from diseased leaves and 

 fruits have produced several organisms including Macrosporium^ 

 Alternaria, Helminthosporium, Aspergillus, Penicillium, Sterig- 

 matocystis, and a bacterium forming brown colonies on date 

 agar. Macrosporium, Alternaria, and Helminthosporium have 

 been shown by inoculations to be actively parasitic on the unripe 

 fruit. It is probable that these fungi break the protective 

 outer layers of the fruit and leaves, and thus open the way for 



