146 Diseases of Truck Crops 



where it has been recently described by Stevenson. x 

 The causative fungus attacks the older and lower 

 leaves, forming numerous irregular, ragged spots 

 (fig. 23 e). 



ROSETTE, see Rhizoctonia, p. 45 



ROOT KNOT 

 Caused by Heterodera radicicola (Greef) Muller. 



This disease is prevalent in the light sandy loams 

 which are infected with eelworm. Small, stringy, 

 bead-shaped knots form on the roots and rootlets. 

 Lettuce thus affected seldom succeeds in heading out, 

 but remains dwarfed and sickly looking. For a 

 further description of the trouble and its control 

 see p. 49. 



DISEASES OF SALSIFY (Tragopogon 

 porrtfolius) 



Salsify, or oyster plant as it is commonly known, is 

 subject to but few diseases, all of which are generally 

 of little economic importance. This is perhaps due 

 to the fact that it is little grown and that its edible 

 qualities are little appreciated by the American 

 consumer. 



SOFT ROT 

 Caused by Bacillus carotovorus Jones 



1 Stevenson, J. A., Journal Department of Porto Rico, I : 93- 

 117, 1917. 



