6o8 MICROBIAL DISEASES OF PLANTS 



Plant on uninfected land and avoid heeling in healthy stock, into soil 

 that has previously borne diseased plants. 



Remvoing the galls results in no practical benefit. 



Olive Knot. 

 Bacterium savastanoi — Smith* f 



The oHve knot has been known for many years, and is even des- 

 cribed by the early Roman writers; its bacterial natiire, however, has 

 been recognized only since 1886. It is most prevalent in those countries 

 which border on the Mediterranean Sea, but it also occurs in the olive 

 growing sections of California. 



So far as is known, the causal organism enters the twigs and leaves 

 of the oUve through wounds, and there produces roughened, wart-like 

 swelUijgs. The growth of the knots usually begins in the spring, and 

 later in the season, if the trees are badly diseased, they show scant 

 foliage, Umited growth, and occasionally dead branches, especially 

 where the galls have entirely encircled the twigs. 



"Fingers and Toes" or "Stump Root" or CABBAOEst 

 Plasmodiophora brassiccs — Woronin 



This organism which is classified as a rhizopod by many is the 

 cause of a common disease of the roots of cabbages and of other, crucif- 

 erous plants. The disease is sometimes called "fingers and toes" and 

 it may cause much damage in market gardens. In it the roots 

 are greatly hypertrophied appearing distorted and lumpy, like fingers 

 bent and swollen with rheumatism. The disease may be controlled 

 to some extent through the destruction, by burning, of all infected 

 material as soon as the disease is recognized. 



It is usually considered well to rely on the rotation of crops or, in 

 case the soil has become generally infested, to plant crops of another 

 type for several years in order to prevent losses from this infection. 

 The plants attacked are recognized by their stunted appearance and 



• Smith, Erw., Bull. 131, Part IV, Bur. of Plant Industry, U. S. Dept. of Agriculture, 1908. 



t Savastano, L. Les maladies de I'olxvier et la tuberculose en particulier. Comp. Rend. 103 

 1144, Iii6. II bacillo della tuberculosi dell'oUvo, nota suppletiva. Rend. Lincei S:92-94 

 1889. 



i Prepared by J. L. Todd and revised by E. E. Tyzzer. > 



