TRANSMISSION AND CONTROL OF BACTERIAL WILT 



OF CUCURBITS ' 



By Frederick V. Rand, Assistant Pathologist, and Ella M. A. Eni^ows, Scientific 

 Assistant, Laboratory of Plant Pathology, Bureau of Plant Industry 



WILT TRANSMISSION 



That the striped cucumber beetle (Diabrotica vittata Fab.) is a direct 

 carrier of the bacterial-wilt organism {Bacillus tracheiphilus) from infected 

 to healthy cucurbits was shown several years ago by Smith.^ He also 

 expressed the conviction that it was the most important, if not the only, 

 summer carrier, and stated the possibility of its serving also as the winter 

 carrier of the disease. Observation and experiment by the senior writer ' 

 during the last two seasons have abundantly confirmed the implication 

 of the striped cucumber beetle as a summer carrier and have brought out 

 strong proof that this insect is not only the principal summer carrier but 

 also the winter carrier of the wilt organism. The twelve-spotted cucumber 

 beetle {D. duodecim punctata L.) must be included with the striped cucum- 

 ber beetle at least as an important summer carrier of the disease. 



INSECT TRANSMISSION 



Relative to cucumber beetles as winter carriers, several direct cold- 

 storage tests have been carried out by the writers in Washington. During 

 the summer and fall of 191 5 hundreds of beetles were collected and 

 placed in cold storage at temperatures ranging from 4° to 10° C. These 

 early experiments were conducted partly with a view to determining 

 the proper conditions of feeding prior to storage and the temperature 

 and humidity most favorable to hibernation in storage. The optimum 

 environment for hibernation varies for different insects, and it is neces- 

 sary to work out this problem for each species. Consequently in these 

 preliminary tests the greater portion of the beetles placed in cold storage 

 was lost. Infection experiments with the few surviving beetles gave the 

 results here detailed. 



Experiment i. — Several striped cucumber beetles were collected in October, 

 1914, and fed about two weeks on cucumber vines {Cucumis sativus) wilting as a 

 result of natural infection with B. tracheiphilus. After six weeks' hibernation in cold 

 storage the five surviving beetles were caged with a young squash plant on which 



' Some of the details of the field experiments at East Marion, N. Y., were carried out by Mr. Wayland 

 C. Brown, of the Bureau of Plant Industry. The land used in these experiments was furnished by Messrs. 

 J. H. Douglass and G. S. Nowell, of East Marion. 



^ Smith, Erwin F. Bacteria in relation to plant diseases, v. 2, p. 215. Washington, D. C, 1911. 



A conspectus of bacterial diseases of plants. In Ann. Mo. Bot. Card., v. 2, no. 1/2, p. 390. 19x5. 



3 Rand, F. V. Dissemination of bacterial wilt of cucurbits. In Jour. Agr. Research, v. s, no. 6, p. 

 257-260, pi. 24. 191S. 



Journal of Agricultural Research, Vol. VI, No. 11 



Dept. of Agriculture, Washington, D. C. June 12, 1916 



eb G— 83 



(417) 



