TOBACCO DISEASES AND THEIR CONTROL. 45 



and if this is maintained for comparatively long periods, especially 

 in relatively warm weather, with tobacco at the clanger point in 

 curing, damage is likely to occur unless the relative humidity is 

 lowered by raising the temperature in the shed by artificial heat. 



Heat is usually applied as open fires under the tobacco. A num- 

 ber of small fires uniformly distributed is preferable to a few large 

 fires. Frequently small pits are dug in the ground in which the 

 fire is placed. Small deflectors above the fire are also desirable. 

 Charcoal, very dry wood, or corncobs may be used, but coal or 

 coke, or material giving dense smoke should not be used with most 

 types of tobacco. The shed is usually tightly closed, except for roof 

 ventilators, which may be left partly open. The length of time fires 

 are kept up will depend on weather conditions, but usually 12 to 24 

 hours will be sufficient to prevent damage. 



STEM-ROT OF CURING TOBACCO. 



In the curing process the midribs or stems of the leaves and the 

 large veins are usually the last to dry or cure out, owing to their 

 thickness. Under normal conditions the moisture given off by these 

 tissues passes off into the air immediately on reaching the surface, 

 but if high relative humidity prevails they become soggy and are 

 therefore a favorable medium for the growth of saprophytic micro- 

 organisms (PL XVI, fig. 2, B and C). This condition does not 

 usually come about until the leaf web itself is quite fully cured 

 out and the greatest danger from shed-burn is over. The midrib 

 has then turned from the normal color, indicating actual death of 

 the tissues. At times, however, the veins decay before the leaf web 

 loses its green color. The saprophytic organisms concerned may be 

 the same as those associated with shed-burn, although this is not fully 

 established. Species of Fusarium, Tricothecium, Botrytis, and other 

 fungi are at least frequently present in dense masses of white and 

 pink growths, often followed in bad cases by bacterial decay. 



Conditions favoring stem-rot and its control are the same as for 

 shed-burn. 



WET-BUTTS, OR FAT-STEM. 



The term " wet-butts " refers to a wet, soggy, and discolored con- 

 dition of the base of the midrib and the veins, but sometimes includ- 

 ing the whole leaf, resulting from the failure of the leaf to cure 

 properly (PL XVI, fig. 2, .4) . As far as known, no careful investi- 

 gation of this trouble has been conducted, but from observation it 

 seems possible that it is due in some cases to freezing weather before 

 the stem is fully cured. This is borne out by the fact that it is 

 the top leaves, generally in late green tobacco, which are usually n f- 

 fectecl in this manner. * In stripping and sorting, the affected leaves 

 are separated and allowed to dry out before being packed, when 

 they are placed in the poorer grades of tobacco. 



When a large percentage of wet-butts is likely to occur in a crop 

 of tobacco it is a good plan to hasten curing with artificial heat 



before freezing weather. 



WHITE VEINS. 



ins 



Occasionally during curing a whitened appearance of the veini 

 of the leaf arises, making it undesirable for cigar-wrapper pur 



