24 MASS. EXPERIMENT STATION BULLETIN 195. 



leaves, bud-scald, and hollow-stalk caused by injury and secondary inva- 

 sions of organisms causing decay, and killing of plants by fertilizer appli- 

 cations. 



Some few of these occur rarely and are of little importance, as, for 

 instance, hollow-stalk, which has been observed only occasionally. Bud- 

 scald was prevalent in the spring of 1919 in some fields which were planted 

 during the extremely hot dry period in the latter part of June. The 

 injury was not noticeable until the plants had been in the field ten days 

 or more. The midribs of the bud-clasping leaflets were the parts most 

 seriously affected, and, as a result of the killing of some of the cells on 

 the underside of the midribs of the leaves which were closed over the 

 bud, these failed to develop naturally, and the normal development of the 

 leaf web and the upper side of the midrib caused the pair of leaves affected 

 to bend sharply do^\Tlward and grow very irregularly. Never more than 

 one pair of leaves was found affected on any one plant. This injury, 

 while sometimes resembling the type of injury caused by bud-worm, is 

 quite distinct from it. Sun-scald of the leaves is, of course, something 

 which cannot as a rule be prevented, and is usually noted on the leaves 

 which have been turned over by the wind, exposing the under side to the 

 hot sun. If water droplets collect on the leaves when in this position, 

 and they are then exposed to the hot sun, there develops on the exposed 

 areas a peculiar type of leaf spot due to burning, the water drops acting 

 as lenses. Fertilizer-burning was noted in a few cases, but was usually 

 found only in seed beds which had been treated with a large amount of 

 quick-acting nitrogen to hasten their growth. Elsewhere in this report 

 are noted observations on the overapplication of ground fish to tobacco 

 beds. Albinism, a condition in which parts of the leaf are almost pure 

 white while the rest of the leaf is normal green in color, has been noted 

 rarely, and its occurrence is of little import. This condition may arise 

 from a variety of causes, and has even been observed as a result of early 

 frosts, but usually the plants outgrow the trouble and develop green 

 coloring matter in the white areas. 



There has been found a root-rot which is more or less similar in its effects 

 to that caused by Thielavia, with the exception that there are no pro- 

 nounced black lesions on the roots, but a more uniform browning and dirty 

 discoloration, most of the injury being found on the fine, feeding rootlets, 

 and not on the larger ones, as is often the case in a Thielavia infection. 

 A form of Rhizoctonia has been isolated from diseased roots, but as yet 

 it has not been possible to make satisfactory reinoculations with the 

 cultures obtained. It would appear, so far as our observations go, that 

 the fungus may be weakly parasitic in nature. There is a "damping-off " 

 trouble, due to Rhizoctonia, which is found in the seed bed, but in this 

 case infection is usually found near the surface of the ground, and often 

 when such diseased plants are set in the field there results, under favorable 

 conditions, the disease of the stem known as "stem-canker." The root- 

 rot apparently due to Rhizoctonia is usually found in restricted localities 



