DISEASES OF PLANTS. 445 



DISEASES OF PLANTS. 



Report of assistant mycologist, II. S. Jackson {Dclaicare Sta. Rpts. 190 Jf- 

 1906, i)/). 70-77. i)ls. 2). — Considerable attention was paid by the author to a 

 nnuil)er of diseases of plants, and notes are sjiven on sun scald and bacteriosis 

 iif plums, fire blight of apples, blight of cantaloupes, double blossom of black- 

 berries aud dewberries, and anthracnose of peppers. 



The author's attention was called in the fall of 1905 to a trouble of fruit 

 trees, affecting phims in pai'ticular. The disease was indicated by the cracking 

 of tTie barlv on the trunk of the tree, usually near the ground, though in some 

 eases extending to the first branches. Investigations were carried on to ascer- 

 tain whether any fungus or other organism was associated witli this trouble, 

 and the conclusion is drawn that it was not due to any specific organism. It 

 is thought to have been a true sun scald caused by the alternate freezing and 

 thawing in the spring of the year, and suggestions based upon the experience 

 of other investigators are given for the treatment of the wounds. 



The fire blight of the apple was investigated, and the disease was recognized 

 as due to the same organism as that causing the fire blight of the pear. The 

 observations made indicated that the infection is very largely through the 

 blossoms and that not infrequently the bacteria spread from one fruit to an- 

 other in the cluster through the peduncles. In several cases the organisms were 

 isolated from the decaying peduncles, and cultures made of them successfully 

 inoculated both apple and pear twigs. 



The blight of cantaloupes described is that due to Macrosporium cucumeri- 

 num, a full account of which has already been given (E. S. R., 14, p. 260). 

 Attention is called to the efficiency of Bordeaux mixture when properly applied 

 in preventing this disease and recommendations are made for its use. 



In 1005 the attention of the mycologist of the station was directed to a disease 

 of plums locally known as bacteriosis. This disease first makes its appearance 

 as dark sunken areas on the younger twigs, which gradually spread, and, as the 

 twig grows, become cracked, enlarging to form a small canker. The disease 

 is not confined to the bark, but extends into the wood, and appears to start only 

 on the first year's growth. Cultures from diseased spots gave abundant colonies 

 of bacteria, and a number of successful inoculations were made from them. 

 It appears from the preliminary study that this disease is of bacterial origin, 

 although the evidence is not yet considered conclusive. It is not known as yet 

 whether this disease is in any way connected with the bacterial spot of the 

 fruit, due to Pftrudornonas prvni, but it is thought that it is not the same as that 

 reported by Jones as due to the pear blight organism (E. S. 11., 14, p. 880). 



Attention is called to the occurrence of double blossoms of blackberry and 

 dewberry, in which there is an abnormal increase and change in the form of 

 the flower parts as well as in the number of branches. The stamens and pistils 

 are usually infertile, consequently no fruit is set. The disease may be detected 

 when the buds are oi)ening, and it is suggested that all canes showing the evi- 

 dence of formation of rosettes or double flowers should be pruned and burned. 



An anthracnose of Cayenne peppers was noticed on truck farms. The disease 

 was found to be due to the fungus Volletotrichiim ni(jntin, which is known to 

 affect the ordinary varieties of red peppers. Spraying the plants with Bordeaux 

 mixture or ammoniacal copper carbonate as the fruit approaches maturity is 

 recoumiended. 



Report of the section of seed control, Hohenheim, 1906, (). Kirchner 

 (Wiirttciiih. Wclinbl. Iji)idu\, 1907, No. 17, pp. .X'/7-3.7.J) . — Tlie principal inves- 

 tigations during the year have been studies of the susceptibility of varieties of 

 wheat to smut and rust, the diseases and insect enemies of clovers, various gar- 

 den and orchard crops, forest trees, and ornamentals, aud the means ft)r their 



