DISEASES OF CULTIVATED PLANTS 468 



fruit, is the main feature of the disease. Scabby pears are perfectly 

 sound and of normal texture and flavor except m the affected parts. 

 The scab growth is very superficial, affecting only the outer surface 

 tissues, which are hard and corky. Such fruit is perfectly healthful 

 and in no way injurious because of the disease, yet on account of 

 their poor appearance, color, and shape, pears which are badly 

 scabbed are almost entirely useless for any purpose, while if at all 

 seriously affected they are worthless for shipping, undesirable for 

 canning, and poor for drying. In years of abundant pear scab un- 

 sprayed orchards have shown losses of from one-fourth to nearly all 

 the crop in marketable pears. The velvety growth on the surface 

 consists of numerous erect threads, which grow up from the surface 

 stratum. At the ends of these threads the oval-shaped spores are 

 produced, which drop off very readily and serve to distribute the 

 fungus. These spores are capable of sprouting when moisture reaches 

 them, and starting the fungus anew. Pear scab fungus also develops 

 upon the bark of the young shoots and twigs of the tree, as well as 

 upon the fruit and leaves, though here it is inconspicuous and not 

 as readily observed as in the latter situations. This fact is of par- 

 ticular importance in combating the disease. 



The usual recommendations for pear^scab treatment, published 

 in bulletins and spray calendars of the various State experiment sta- 

 tions, call for spraying with Bordeaux mixture just as the buds ex- 

 pand, again after the blossoms have fallen, and a third time about 

 two weeks later. This refers to spraying for scab alone, without 

 reference to insect pests. In California the spraying of pears for 

 scab has been largely along the line of general treatment for the 

 eradication of all pests, definite or indefinite. To clean up the tree 

 is a popular expression of the object of most pear-tree spraying, ex- 

 cept the use of paris green for worms. More definitely stated, the 

 usual practice of pear spraying consists in treatment with lime- 

 sulphur in January for scale, scab, moss, softening the bark, and a 

 general clean up. This is applied by some every year, by others 

 once in two or more years, and in still other cases not at all. Beyond 

 this two or three sprayings with paris green and lime are made in 

 summer after the fruit sets, adding bluestone for scab and general 

 results. 



The results of this treatment have not been entirely satisfactory 

 in relation to scab control. While the disease has varied in abun- 

 dance from year to year, orchards sprayed in this way have shown 

 much scab in years when it was abundant and considerable losses 

 have resulted. Neither the early-winter lime-sulphur treatment, or 

 the summer paris green, bluestone, and lime spray, or the combina- 

 tion of the two, has shown decidedly satisfactory results in scabby 

 seasons when closely followed up, although such treatment has been 

 better than none at all. (Cal. E. S. B. 163.) 



Crater Blight. This term is a rather common one among pear 

 growers, but is not applied to any very definite form of disease. It 

 is supposed to signify a dying of certain spots or patches of bark sit- 

 uated on the limbs or trunk. In these patches the bark becomes 



