BUREAU OF PLANT INDUSTRY. 173 



WATERMELON DISEASES. 



During the past season a special effort has been made to educate 

 the southern grower in the methods of controlling the two most 

 serious diseases of watermelons, anthracnose and stem-end rot. The 

 Melon Distributors' Association, the United States Railroad Admin- 

 istration, and the State extension departments cooperated in this 

 work. A field campaign was carried out, through which the methods 

 for the control of these diseases w^ere brought to the attention of the 

 public by means of posters, printed cards, bulletins, and lantern 

 slides. In the case of stem-end rot an effort was made to secure the 

 stem treatment with disinfectant paste of all melons shipped from 

 Georgia, Florida, South Carolina, and Alabama, the four States 

 which' have suffered most from this disease in the past. It is esti- 

 mated that in 1918 more than 2,500 carloads of watermelons, almost 

 20 per cent of the total shipments from these four States, rotted in 

 transit, the chief trouble being stem-end decay. The results to date 

 of the inspection of cars treated this season show that the loss in 

 these cars has been reduced to less than 1 per cent. A very general 

 application of the stem treatment has been made possible by the fact 

 that the United States Railroad Administration required the pre- 

 payment of the freight on untreated carloads. 



Spraying for the control of watermelon anthracnose was also car- 

 ried out this season under the supervision of our field assistants on 

 approximately 3,400 acres of melons in Florida with satisfactory 

 results. Tests of the practicability of seed treatment on a commercial 

 scale for the control of watermelon anthracnose are being made on 

 areas comprising about 2,000 acres in Indiana, Missouri, and Arkan- 

 sas which have been planted with seed disinfected with mercuric 

 clilorid. 



CUCUMBER DISEASES. 



The investigation of cucumber diseases, extending over several 

 seasons, has yielded important results within the past year. Three 

 of the most destructive and widespread diseases, mosaic, anthracnose, 

 and angular leaf-spot, have received major attention. A prominent 

 development in the study of the mosaic disease has been the discovery 

 of a method of overwintering. The results of recent work have 

 shown that a considerable percentage of seed from mosaic plants of 

 the wild cucumber may produce diseased plants the following spring. 

 In this way the first mosaic centers are established, from which the 

 disease is later carried to the cultivated crop in the near-by fields by 

 the striped cucumber beetle and other insects. Additional evidence 

 has been secured that the disease is also carried over winter in the 

 seed of cultivated mosaic cucumbers. 



Continued studies of cucumber anthracnose and angular leaf- 

 spot have proved that these diseases live over winter in the soil on 

 dead diseased plants and other refuse and that they are also carried 

 on the seed from infected fruits. A successful and practical method 

 of seed disinfection by means of mercuric chlorid has been worked 

 out and applied on a commercial scale, with successful results in the 

 control of both these diseases when combined with proper rotation 

 of crops. 



