126 SEVENTEENTH REPORT. 



knowu in one locality for 7 years. The striking character of the 

 disease and the familiarity of the growers AA-ith it, make this fignre 

 reliable. No parasite has been associated with the disease. The 

 stndy of this disease is being ccmtinued. 



The loss brought about bv this disease is extremelv heavv. It 

 usually shows up in tields before the vines have reached the height 

 of yield, and once api)eariug, there is but a short time of profitable 

 growth. In the locality in Allegan county where the disease is 

 worst, the annual yield has been decreased more than 50 per cent. 

 As a loss throughout the state, its etfect is smaller, because as yet 

 its distribution is restricted to a few counties about Grand Rapids. 

 Potentially it seems to be the most serious disease of the plant. 



Cucuinher ^Scah. Cucumber scab due to the fungus VUKlmporium 

 eucumerininn Ell & Arth. did great damage to the crop, chiefly in 

 the counties north of Grand Rapids. This distribution corresponds 

 very well with the area which had frequent rain in August and 

 sub-normal temperature. A full discussion of this disease is given 

 on another page of this report. 



CELERY DISE1.VSES. 



Stunting Disease. A celery disease has been prevalent about 

 Kalamazoo for at least 5 years which differs from the ordinary 

 celery troubles. The disease mav have been described before but 

 the reports are very contradictory. 



The disease manifests itself by a stunting (PI. YIII) of the 

 affected plants, beginning always in the seedling stage. The vas- 

 cular system of the main root and of the heart is discolored, and 

 the discolored fibres may be traced up the leaf stalks. Sometimes 

 a lateral root is affected, and then the discoloration is found to be 

 only upon one side. Microscoi)ical examination of thin sections 

 of the vascular tissues show the tubes to be plugged with rod 

 shaped bacteria. Plants with a plugged vascular system, with the 

 inception of active growth fi-equently split and the pithy heart 

 dries out, becoming a rusty red. If the conditions be wet, the 

 plants with cleft hearts rot with the ordinary secondary rots. Insects 

 are found associated only at this stage. The stunted portion of 

 the plants does not grow vigorously but lateral buds may start and 

 grow vigorously after the de\elopment of a new root system. The 

 disease does not progress noticeably in the older plants. A 

 ])lant which starts to grow after the central portion is rotted sel- 

 dom becomes marketable. 



The <liseased plants become esi>ecially noticeable l>ecause of the 



