DISEASES OF PLANTS. 887 



experiments have been conducted relating to its occurrence and infectious nature. 

 The experiments show that all diseased plants in the plant bed should be removed, 

 and wherever diseased plants are found in the field they should be immediately 

 destroyed. The experiments showed that the disease could be communicated by 

 the experimenter touching a number of diseased plants and in quick succession 

 touching those that showed no evidence of the trouble. This fact shows the impor- 

 tance of the destruction of all infected plants, so that the disease may not be dis- 

 tributed. 



Among the parasitic diseases the root rot, due to Thielavia basicola, and the bed 

 rot, due to Rkkoclonia sp., are described at some length. In addition notes are 

 given on the decay of tobacco seedlings, which is attributed to Altemaria /nuns, the 

 Granville tobacco wilt, which it is said has been observed in a few places in Ohio, 

 the leaf blight due to Cercospora nicotianse, white speck and brown spot caused by 

 Macrosporium spp., and downy and powdery mildew caused respectively by Erysiphe 

 communis and Phytophihora nicotianae. Few of these parasitic diseases have been as 

 yet noted in Ohio. 



A brief account is given of the parasitism of the broom rape (Orobanche ramosa), 

 which is reported as occurring in tobacco fields in a number of places within the 

 State. A previous account of this parasite has been given in Kentucky Station Bulle- 

 tin 105 (E. S. R., 15, p 159). 



In order to call attention to some of the troubles experienced in the curing house, 

 the author briefly summarizes from various sources descriptions of the pole burn or 

 pole rot and stem rot, both of which are sometimes quite destructive. 



Pear scab, K. E. Smith (California .V". Bui. /'<'.;, /»/-. 18, figs. .'>)•— One of the most 

 serious diseases of the pear in California is the pear scab, and the present bulletin 

 aims to give the results of some observations on the occurrence and treatment of this 

 disease in California, based upon the observations of the author in numerous 

 orchards, together with investigations carried on in cooperation with the experiment 

 station. 



After describing the fungus (Fusicladium pirinum) and its effect upon the pear, 

 the author takes up the subject of the control and shows that in California the usual 

 recommendations published in bulletins and spray calendars can not lie successfully 

 followed. These usually call for spraying just as the buds expand, a second appli- 

 cation after the blossoms have fallen, followed by a third about two weeks later. 

 Where these directions have been followed the results have not been entirely 

 satisfactory. 



The author has carried on some investigations relative to the time of spraying, and 

 the results of Ins work are quite instructive. A study was made of the different 

 stages of the pear buds from the time they first began swelling until the blossoms 

 began to open, and it was found that successful sprayingshould begin in what is termed 

 the second stage of bud development. This is just at the time when the bud scales 

 have separated and the first indication of the young growth appears. Other 

 applications should be made from time to time as necessity demands. 



In conjunction with the work for the prevention of the scab the author considers 

 the use of lime, sulphur, and salt for insect enemies, particularly the codling worm. 

 This treatment, followed by the use of Bordeaux mixture, will give a crop of clean 

 fruit in nearly every instance. As a precautionary measure the author suggests the 

 plowing under or burning of all the dead leaves and thorough spraying with lime, 

 sulphur, and salt as late in winter as possible, followed by Bordeaux mixture, two appli- 

 cations to be given while the buds are unfolding and others if needed. Ordinarily 

 the two applications will be found sufficient. If only a single treatment of Bordeaux 

 mixture can be given the earlier spraying of Bordeaux mixture will prove the more 

 effective. 



