A Bacterial Disease of Stone Fruits 395 



twigs sometimes showed one or more blackened, slightly sunken areas. 

 These often measured as much as seven millimeters in width and extended 

 from five to fifty millimeters along the stem, in some cases the entire 

 end of the twig being blackened. Cultures from these areas produced 

 yellow bacterial colonies. 



On taking up work at the Missouri State Fruit Experiment Station in 

 1906, the writer observed that the twigs of some varieties of peach and 

 plum in Missouri also showed blackened, sunken areas, and poured plate 

 cultures from the diseased tissue in many cases gave yellow bacterial 

 colonies. About the middle of June, 1906, it was observed that the 

 foliage of trees bearing the diseased twigs had developed the shot-hole 

 condition to a marked extent, while the foliage on trees with twigs free 

 from the blackened areas was quite free from shot-hole. The fruit on 

 Abundance and Burbank plum soon developed many typical black-spot 

 areas, from which pure cultures of a yellow organism were easily obtained. 

 A little later many peach fruits developed numerous small cracks. These 

 were at first supposed to be due to the work of curculio, but a careful 

 examination showed bacteria to be present in enormous numbers. 



A careful study soon proved that the organism had invaded the apricot 

 and the nectarine in much the same way as it had the peach and the 

 plum. The fruit of the nectarine in the station variety orchard in 1906 

 was so badly cracked as a result of the attack of this organism that the 

 entire crop was destroyed by various decay organisms long before the 

 ripening period. Some of the apricot fruits developed the typical black 

 spot. The twig cankers on both apricot and nectarine were fully as 

 plentiful as on the peach, and premature defoliation also occurred on both 

 apricot and nectarine trees. 



Nomenclature 



Since bacteriologists have not yet adopted an international code of 

 nomenclature, it does not seem advisable to enter here into an extended 

 discussion of the limits of genera, the selection of types, or the position 

 of this organism in the various systems of classification proposed. The 

 writer has therefore elected to follow arbitrarily the suggestion given by 

 Erwin F. Smith (1905a). The organism was first described by Smith 

 (1903) under the name Pseudomo7ias Pruni. Later, however, it beeame 

 Bacterium Pruni, when Smith substituted the generic name Bacterium 

 Colin emend, for Pseudomonas Migula. 



