3o6 Journal of Agricultural Research voi. xiii, No. s 



In addition to spraying, certain sanitary measures should be adopted. 

 Diseased vines should be destroyed, if possible, in the fall. Crop rota- 

 tion should be practiced. Vines should not be disturbed when wet with 



dew or rain. 



SUMMARY 



During the summers of 191 5 and 191 6 the attention of the writer was 

 called to a peculiar leafspot on cucumber that was doing more or less 

 damage to cucumber fields in the vicinity of Plymouth, Ind., and Bowl- 

 ing Green, Ohio. The spots vary in diameter from 0.2 to 15 mm. 

 The small spots, ranging from 0.2 to 3 or 4 mm. in diameter, may 

 be circular or angular in outline. The center is light yellowish 

 brown, surrounded by a reddish-brown border; rarely, the spot is nearly 

 white. The larger spots are usually nearly white or tinged with brown, 

 with reddish-brown areas along the veins and frequently with brownish 

 centers, giving the spots a mottled appearance. From these spots a 

 fungus belonging to the genus Stemphyliura has been isolated. The 

 parasitism of this fungus to the leaves of cucumbers, gourds, and squashes 

 has been repeatedly demonstrated by successful inoculations. Four 

 varieties of cucumber, two of gourd, and two of squash have been success- 

 fully inoculated. So far as ascertained, no data regarding this disease 

 has been published hitherto, and the causal organism is described as a 

 new species under the name " Sieniphylhim cucurbitacearum." 



Cultural work with this fungus has shown that high temperatures and 

 a dry atmosphere are unfavorable to its development. Consequently 

 serious trouble may be expected only in cool weather, especially when 

 combined with abundant moisture. 



The fungus lives over the winter in or on the diseased vines. The 

 spores are disseminated by wind, rain, insects, etc. 



Preliminary experiments have given promise that this disease may be 

 controlled by Bordeaux mixture. In addition to this, sanitary measures 

 such as the destruction of diseased vines and crop rotation, as well as 

 the avoidance of work among plants when wet, should be practiced. 



