EXPERIMENT STATION REPORTS. 271 



year due to this disease. On a small acreage sprayed under the direc- 

 tion of this department the cooperating grower saved a crop worth 

 $1500. This bulletin has been printed in both English and Dutch edi- 

 tions. Dr. Eichard deZeeuw of this department kindly prepared the 

 Dutch edition. 



A serious root rot of celery caused by an undescribed species of Phoma 

 was discovered at Kalamazoo. The etiological relation of the Phoma 

 has been proved. Further study of this fungus is now being planned. 



Completion of tlie celery project is contemplated for this next year, 

 and it is hoped that funds will be provided so that the serious celery dis- 

 eases can be investigated. 



The division is cramped for room, not only in laboratory but also in 

 greenhouse. The growing needs of our work should be recognized in the 

 building program of the College. 



Very respectfully, 



G. H. COONS, 

 Eesearch Assistant in Plant Pathology. 



East Lansing, Mich., June 30, 1916. 



NOTES ON MICHIGAN PLIANT DISEASES FOR 1915. 



POTATO DISEASES. 



The peculiar inheritable malady of the potato known as Potato Mosaic 

 was found very widespread in the Upper Peninsula. In one field 80% 

 of the vines showed the disease, and the yield was cut more than half. 



Another disease of the same type was found at Manistique. A cer- 

 tain shipment of Eusset Eural potatoes has consistently thrown a num- 

 ber of plants for the last two seasons showing a peculiar proliferation of 

 the shoots. The potato vines lose nearly all their characteristic appear- 

 ance and become stunted clumps made up of a great many wiry shoots. 

 The leaves are so small, that the vines take on the appearance of a clump 

 of chickweed. The disease differs from the spindling sprout disease de- 

 scribed by Stewart, in that a sort of witch's broom is produced instead 

 of merely a. weak primary sprout. The tubers produced on a vine are 

 small, and according to the testimony of a grower, reproduce a similar 

 witch's broom. 



Potato tubers injured by the rhizomorphic strands of Armillaria mel- 

 lea have been found for the past two seasons on newly cleared soil 

 planted to potatoes. This trouble is probably more of curiosity than a 

 disease to cause serious loss. 



A rotting of potatoes in the field was found to be associated with a 

 Phoma on the stem. The organism was cultured and found to be slightly 

 pathoenic to potato tubers kept under ordinary laboratory conditions. 

 The disease diff'ers from that recently mentioned by Melhus. The causal 

 organisms when grown in comparison cultures were found to be differ- 

 ent. 



Last season much more than one-half of the potato crop was destroyed 

 by the Late Blight. Data have been collected from potato shippers and 



