VASCULAR DISEASES. 



WILT OF CUCURBITS. 



(Synonyms: Cucumber-wilt; Cantaloupe-wilt; Squash-blight; Pumpkin-blight). 



DEFINITION. 



This is a specific communicable disease of cucumbers, squashes, and some allied plants. 

 It is characterized by the sudden wilting and shriveling of the foliage and by the presence 

 in the vascular bundles of enormous numbers of a white sticky bacillus which is the cause 

 of the disease. 



HOST-PLANTS. 



This disease has been observed in cucumbers (Cucumis sativus), muskmelons (Cucumis 

 melo), pumpkins (Cucurbita pepo), and squashes (Cucurbita moschata and C. maxima). 

 The disease has been successfully inoculated by the writer into all of the above mentioned 

 plants many times over and into the following additional cucurbits : Cucumis odoratissimus, 

 Benincasa cerifera, Cucumis anguria, Cucurbita foetidissima, C. californica, Sicyos angulatus 

 and Echinocystis lobata, the last four being wild plants of the United States. The disease 

 is not known to the writer to occur in the watermelon but it has been reported by Selby. 

 Inoculations into this plant, while sometimes producing a wilt of the pricked leaf generally 

 failed to induce any secondary wilt. In one or two instances other leaves than the inocu- 

 lated ones wilted and the vessels were found plugged by a bacillus. Often there was no 

 wilt even in the punctured leaves. Inoculations from virulent cultures into the following 

 cucurbits failed, or produced only local injuries from which the plants recovered : Melothria 

 scabra, Cucumis erinaceus, Luff a acutangula, Momordica balsamina, Lagenaria vulgaris, 

 Trichosanthes cucumeroides, Apodanthera undulata. The disease is not known to occur 

 in any wild plant, but it is so very easily inoculated into Sicyos angulatus and Cucurbita 

 foetidissima that it should be searched for on these plants and on other wild cucurbits. 



Inoculations into non-cucurbitaceous plants such as Solanum tuberosum, Lycopersicum 

 esculentum, Datura stramonium, Passiflora incarnata, Vigna catjang, Nicotiana tabacum, 

 Pyrus orientalis and Hyacinthus orientalis yielded only negative results. The disease is 

 not known to occur outside the Cucurbitaceae, and probably many species of plants within 

 the limits of this family are not subject to it. 



GEOGRAPHICAL DISTRIBUTION. 



The limits of this disease are not known. It occurs in Canada, Massachusetts, Ver- 

 mont (?), Connecticut, New York, New Jersey, Delaware, Maryland, Virginia, West Vir- 

 ginia, Pennsylvania, Kentucky, Ohio, Indiana, Illinois, Michigan, Wisconsin, Missouri, 

 Iowa, Nebraska and Colorado. It is not known to occur south of latitude 35 and it is 

 believed to be restricted in its southern distribution by the fact that the bacillus is very 

 sensitive to heat. It should be searched for, however, in the Gulf States. The disease has 

 been reported from Germany by Dr. Otto Appel; from Russia, near St. Petersburg, by 

 Dr. Iwanoff ; and it is to be looked for in all north-temperate regions where cucurbitaceous 

 plants are grown and where the temperature to which the vines are exposed does not exceed 

 the thermal death-point, or the maximum temperature for the growth of this organism. 



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