72 THE CULTURE OF TO IS AC CO. 



the soil, as produced by bacteria or induced by faulty drainage. 

 Recently Dr. Woods, of the United States Department of Agri- 

 culture, who has carefull}' investigated the disease, has aiTived at 

 the conclusion that it is due to none of the generally supposed 

 causes, but that it is "due to defective nutrition of the young 

 dividing and rapidly growing cells, due to a lack of elaborated 

 nitrogeneous reserve fo(.id, accompanied by an abnormal inciease in 

 activity of oxidising enzymns in the diseased cells." These ai'e the 

 same enzymns that prove so beneficial in the fei'mentation pi-ocess 

 later. The enzymns are liberated by the decaying plants or i-oots, 

 and, if in excess, may enter the roots of young plants .set in tiie 

 same sciil, and induce a diseased condition, from which the plant 

 will never completely recover. Plants with injured ro<jts are more 

 than commonly susceptible to attack. 



The sowing of seed on fi-esh or bui'ned plant beds, the avoid- 

 ance of injury to roots in transplanting or in cultivation, and 

 the making of conditions favourable to a steady, even growth, 

 appear at present to be the only things within the leach cjf the 

 planter foi' the prevention or moderation of this condition. 



Seed from diseased plants should not be saved, f(ji-, while the 

 disease may not be cai-ried in this manner, still an inheiited 

 tendency to this condition may be ti-ansmitted. 



" Frog Eye," or Leaf Spot. — This disease is also called " white 

 speck," because fif its appearance in the form of small white specks in 

 the tissue of the leaf. It appeal's to a ceitain extent in neai-ly all 

 tobaccos and does nf>t do any large amount of damage. A few j-eai's ago 

 cigar tobacco with this specking was in demand, but the style changed 

 as soon as it was found possible to ai'tificially produce this mai'king<;in 

 any leaf. It is supposed by some to be caused by too much water- at the 

 tap root, and by others to be due to the presence of an excess of potash 

 in the soil. It does not appear, however, that it is due to either of 

 these causes, and is probably bacterial in its nature. This specking 

 must be differentiated from the small white specks due to sun 

 burning where there has been a particle of sand upon the leaf. No 

 successful treatment is yet known. 



Rust, or Blight.— There are two or three forms of w hat are known 

 as rusts, or lilights, which are physiological conditions caused either 

 by excessively dry weather, or excessively Avet weather, or bv the use 

 of too much of cei'tain fertilizei-s. The farmers of South' Cainlina 

 say that the use of lai-ge amounts of phosphates will cause the plants 

 to preniatuiely ripen, which is sometimes called blight. The analysis 

 of the conditions present in the lield and the removal of the cause as 

 far as possible is the only treatment. 



There are several minor diseases (jf growing tobacco, but thev can 

 hardly be considered of interest unle.ss they make their appearance in 

 Ehodesia. 



Diseases of Tobaeeo while Curing (Pole Burn, Pole Sweat, 

 or House Burn).— Pole burn in the tobacco barn is due to excessive 

 humidity, and is very likely to be present during prolonged warm wet 

 weathei'. The disease is first noticed by the appearance of small dark 

 spots near the stem and mid-rib. The spots rapidlv increase in size 

 and numbers, and in a short time become continent. Within fort^-- 



