182 



BACTERIAL DISEASES OF PLANTS 



h-^^ 



Fig. 125. — Dwarf nastur- 

 tium plant wilted by Bacter- 

 ium solanacearum. From a 

 garden in Baltimore in 1914. 

 (See paper by M. Katherine 

 Bryan in Journal of Agricul- 

 tural Research, August, 1919, 

 p. 451.) 



It prevails under the equator and 

 in the North and South Temperate 

 Zones, but its northern and southern 

 distribution are unknown. It seems to 

 thrive best in the Eastern United States 

 on washed river sands. In the Old 

 World it is believed to occur from Japan 

 and the Philippines to New Zealand 

 and westward through Java, Sumatra 

 and India to South Africa and Italy (?). 

 In the United States it occurs from 

 Maryland and New Jersey south to 

 Florida, Cuba and Porto Rico, but its 

 northward and westward distribution 

 in this country are unknown. It has 

 not been reported from South America 

 but undoubtedly it occurs there. Prob- 

 ably its range is that of the plants sub- 

 ject to it. 



Cause. — This disease is due to Bac- 

 terium solanacearum EFS. This is a 

 non-viscid, motile, polar flagellate, white 

 (bluish, brownish, opalescent), non- 

 sporiferous, slow-growing, non-lique- 

 fying (or very slowly liquefying?), non- 

 starch-destroying, aerobic, milk-clearing 

 (non-curdling) nitrate-reducing, non- 

 gas-forming, rod-shaped schizomycete, 

 forming on the surface of agar-poured 

 plates small circular, or rather nearly 

 circular (Fig. 132) smooth, wet-shining, 

 opalescent colonies (white by reflected 

 light, pale brownish by direct trans- 

 mitted light, bluish or pink-opalescent 

 by oblique lighting). Although white 

 at first by reflected light, the surface 

 colonies become brown through the for- 

 mation of a dark colored, water-soluble 



