314 STATE BOARD OF AGRICULTURE, 



LETTUCE. 



Andiiaciioso or shot liole of let luce (Marsfioiiina imnaiioniana) was re- 

 ])oit('(l 1ml once in IDKJ. l<N)nu(M'ly this <lisease occurred everj'where in 

 jMichi^an greenhonses. At juvscnt its occurrence is only occasional, 

 and then usnally associated with leaky <;ntters. It wonld seem since 

 it is known that the disease is readily dispersed by hose watering, that 

 the diminntion of this disease may properly be correlated with the in- 

 ci-ease in amonnt of overhead watering systems. 



One case of the disease was found in a garden near the College. The 

 plants were grown on soil which had never before borne a lettuce crop 

 and from one plant the disease spread along the row. No wild lettuce 

 grew near. In absence of any report of the fungus on other hosts, the 

 possibility of seed transference seems probable. 



Lettuce Stunt: 



In the 1915 Report of the Michigan Academy of Science I described 

 a new disease of greenhouse lettuce which is at present commonly as- 

 scribed to Khizoctonia injury. In that publication it was presumed that 

 bacteria stand in causal relation to this malady. Repeated cultures 

 failed to give any one bacterial organism with any degree of regularity. 

 From bits of tissue in practically every culture attempted a rapid grow- 

 ing Phycomycete has been obtained. This organism is a typical Pyth- 

 ium. Time has not been available for inoculation experiments, but it 

 seems likely that the disease found is associated with this known para- 

 site. 



Many circumstances contribute to this assumption. The disease is 

 severe when seedlings are watered abundantly, and is checked when the 

 seedlings are kept "on the dry side." Plants near leaky valves or leaky 

 gutters may show the disease while the drier parts of the beds have sound 

 plants. The disease is commonly contracted in the seed bed, but may 

 arise from wet conditions in plants half grown, or even older. Since 

 wet conditions seem to be essential to infection, the control is obvious. 

 It has been put in practice with marked success by several greenhouses. 



CELERY. 



The Celery Stunting Disease increased in extent until practically no 

 fields in Kalamazoo are free from infection. This came about largely 

 from flooding. The wet weather of 1915 may have been important in 

 bringing about greater dispersion by the tracking of mud from field to 

 field. All second crop and third crop celery of Golden Self-blanching 

 celery planted in affected fields was practically a failure. The disease 

 w^as found at Grand Haven, Jackson, Bay City and Portage, Michigan. 

 In view of the wholesale interchange of plants in celery districts, it is 

 likely that the disease will be widely introduced throughout the state. 



Celery Blight {Septoria apii) did enormous damage last year. The 

 enormous infestation of the first crop which occurred on account of the 

 wet weather in the early half of the season, brought about considerable 

 infection of the second crop. Heavy rains in the fall in conjunction with 

 the scattering foci of disease which existed, led to an epidemic of great 

 severity in all the celery districts. In the Kalamazoo district alone 

 $25,000 in claims were filed against a railroad company for rotting in 

 transit. This was largely on second and third crop celeiy. As this rotting 



