EXPERIMENT STATION REPORTS. 313 



Only two or three plants were seen. The disease is characterized by 

 dwarfing of the affected i)lants Avhich show black streaks on stems and 

 petioles and occasionally in the leaf veins themselves. 



No Mosaic was seen last' year althongh stocks which showed Mosaic 

 the preceding year were examined. It is believed that weather condi- 

 tions masked the signs by which we diagnose the disease. 



TOMATO DISEASES. 



Point Eot or Blossom End Rot was reported from many sections in 

 the southern half of the state. The disease was clearly associated with 

 drought conditions. 



Many growers complained of failure of the blossoms to set fruit. This 

 seemed to be associated Avith the unusual w^eather conditions at time of 

 pollination. 



CUCURBIT DISEASES. 



Work on cucumber diseases was carried on as before in cooperation 

 with the U. S. Department of Agriculture at Big Rapids. No serious 

 epidemics of cucumber diseases occurred. Cucumber Scab occurred only 

 in small amount, and cucumber Mosaic although present did not ruin 

 the crop. No report of Downy Mildew was made. Considerable com- 

 plaint was made on account of a Tip Burn or Leaf Scorching which was 

 undoubtedly to be ascribed to the drought conditions. 



On seed farms near Jackson diseases of cucumber and muskmelon were 

 very important. Anthracnose on certain varieties of muskmelon (Em- 

 press) destroyed the crop. Anthracnose on the cucumber fruits, which 

 has not been rej^orted commonly, occurred in sufficient amount to greatly 

 lessen seed production. 



Angular leaf spot was found in many localities and was described by 

 correspondents as doing severe injury to seedlings. 



A disease caused by a yellow bacterial organism was also sent to the 

 station. In this disease brown watery spots occurred on the fruit, 

 usually associated with a lenticel. From such diseased spots beads of 

 dark reddish brown gum emerged. The affected fruits softened and rot- 

 ted in the course of a few days. The organism was obtained in pure cul- 

 ture and characteristic lesions produced by inoculation experiments. The 

 germ seems distinct from Bacillus lachrymosus and from the organism 

 described by Burger as causing rot of cucumbers in Florida. 



A new disease of watermelon was discovered by Mr. Ray Nelson, grad- 

 uate assistant in the experiment station. Watermelons affected with 

 this disease show blackened, withered spots commonly at the point 

 where the blossom was attaclied. This spot increases in size until the 

 whole melon may be involved. Usually the disease only progresses far 

 enough to cause a blemish about ?/' in diameter. The cause of this dis- 

 ease is a Pythium, probably PytJiium dehanjanum. The causal organ- 

 ism has been obtained in pure culture, its pathogenicity proved, as well 

 as its ability to attack fruits of other plants of the cucurbit family. The 

 organism does not produce a "leak" of potato. 



The disease has been observed in several fields. Its economic import- 

 ance is not known. It will probably be found to be wide spread and ser- 

 ious, not only in Michigan, but in the centers of watermelon production. 

 Mr. Nelson is continuing his observations on this disease. The fungus is 

 being grown in pure culture in the laboratory and further publication is 

 promised. 



