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BULLETIN 1256, U. S. DEPARTMENT OF AGRICULTURE. 



HOLLOW-STALK. 



Description. — Hollow-stalk is a fairly common disease in most 

 tobacco districts, but it is rarely important, usually occurring only on 

 a few isolated plants. This disease is referred to in some of the old- 

 est literature on tobacco culture, in which it is usually attributed to 

 water-logging of the soil. The disease is characterized by the decay 

 of the pith of the stalk in particular. It most commonly occurs on 

 full-grown plants, where the entire pith may be rotted out, leaving 

 the stalk hollow (figs. 6 and 7). Quite frequently the symptoms 

 appear in the leaves, as indicated by wilting only, but occasionally 



the actual rot extends into the 

 veins of the leaf. The rot may 

 start either from the base or from 

 the top of the stalk, but usually 

 through wounds produced either 

 by insects, by accidental breaking 

 of the leaf, or by the topping or 

 suckering operations. 



Cause. — Hollow-stalk has been 

 shown to be due to the invasion of 

 bacteria of the common soft-rot 

 type which produce decays in 

 many vegetables, especially in car- 

 rots and cabbages, during storage. 

 While the organism causing hol- 

 low-stalk has not been carefully 

 studied, it is similar to the soft-rot 

 organism in the common charac- 

 ters, and the soft-rot organism 

 from carrots will produce the de- 

 cay of tobacco pith. Hollow-stalk 

 is therefore attributed to Bacillus 

 caiotovorus. 



Conditions favoring the dis- 

 ease. — "Wet or poorly drained 

 soils no doubt favor infection, and 

 continued wet weather f avors both 

 infection and rapid growth, which 

 in turn would produce a succulent 

 pith. Relatively high tempera- 

 tures accompanying such moist 

 weather also favor the disease. 

 When plants are topped or suck- 

 ered during such periods of weather, exceptionally favorable condi- 

 tions for infection through the wounds produced occur before they 

 can lieal sufficiently. While only a very few isolated plants affected 

 with hollow-stalk occur before topping, the disease is commonly 

 spread to many neighboring plants in topping and suckering, the 

 infective material being carried on the hands of workers from one 

 plant to another. 



Control. — The only measure of control which is ordinarily worth 

 while practicing in the case of hollow-stalk is to take precautions 

 againsl spreading the disease from plant to plant during topping 

 and suckering. This is best done by leaving the topping and sucker- 



I 



Fig. &. — Section of a stalk of a tobacco 

 plant (at left), showing the complete de- 

 struction of the pith by hollow-stalk. 

 Compare with the section of a healthy 

 stalk shown at the right. 



