576 STATE BOARD OF AGRICULTURE. 



Van Hook's descriptions, his photographs of diseased plants, and the en- 

 vironmental conditions under which the disease became destructive, fur- 

 nish evidence conclusive enough to justify the assumption that he was 

 dealing with the Phoma Root Rot which has been reported from the celery 

 growing regions of Michigan and New York. 



In 1914, Coor.s (2) discovered Phoma Root Rot in the celery fields at Kal- 

 amazoo and in 1916 at Byron Center, Michigan, where the disease had been 

 seen by growers for several years. The following seasons the disease was 

 again found in fields at these places, and it has been present, causing more or 

 less loss, each season since it was first noted. In 1918 the author observed 

 cases of the disease at North Muskegon and Portage, Michigan. 



Dye and Whetzelf in 1918 reported the disease as present in New York 

 State. Again in 1919J Phoma Root Rot was reported from the celery dis- 

 tricts of Ohio, where it seems the disease is more or less prevalent, depending 

 on weather and soil conditions. As yet, no mention of the disease has been 

 made from the southern celery growing sections or from the Pacific Coast. 



Outside of the United States, our knowledge of the disease is restricted to 

 the northwestern part of Europe. Klebahn (5) described Phoma Root Rot 

 on celeriac gro%\Ti in Hamburg lowlands. It seems to have a general distri- 

 bution over Holland and southern Germany, where it has caused serious 

 loss to the growers of turnip-rooted celery. Quanjer and Slagter (6) de- 

 scribed the disease from Holland and state that it is generally distributed 

 in that country. 



Economic Imi-ortaxce. 



The sporadic occurrence of this disease makes it impossible to give even 

 an approximate estimate of annual loss. The seriousness of the attack 

 after infection depends almost entirely on environmental conditions. In 

 cool, wet seasons, the loss may reach 100 per cent in an infested district; 

 under other conditions, the loss may be negligible. 



The disease in America has never been so serious as in Europe. Klebahn 

 (5) and Quanjer and Slagter (5) report considerable damage to celeriac oc- 

 curring at more frequent intervals than has been noted in America. Many 

 plants are rotted off at the base, while the damage done by stunting and 

 pruning away of the outer leaves, calls for serious consideration, reducing 

 as it does the market value of stalks so greatly. 



Several rather severe outbreaks of this disease have been recorded in Amer- 

 ica in certain localities. Van Hook reports that in the celery districts of 

 Ohio in 1902 one grower suffered a loss of 75 per cent of his crop; minor 

 losses were reported from other sections. At Kalamazoo, Michigan, in 

 1914, and again in 1915§ the first crop on an area of three acres was a com- 

 plete loss. At Kalamazoo and Byron Center, Coons (3) states that the 

 disease was very severe in the spring of 1917. In the past three seasons the 

 disease has been present in a number of celery fields which have been in- 

 spected, but diseased plants have shown nothing more than black rings 

 around the base. These seasons have been rather dry and warm in the 

 early part of the summer ; this no doubt accounts for the scarcity of the dis- 

 ease during these years. Where the disease producing organism is known 

 to be present, growers should expect to encounter loss in cool, wet seasons 

 if due precautions for protection are not taken. 



t Verbal statement to Dr. G. H. Coons. 



t Plant Disease Bulletin, Supplement 3, p. 108, 1919. "Scab, caused by Phoma apiicola Speg . 

 (sic) was recorded on celery from Ohio." 

 § Verbal report to the author. 



