DISEASES OF PLANTS. 1045 



result of demonstration experiments conducted in the Middle West in 1906, the 

 :iuth()rs determined that apple blotch was far more destructive than apple scab 

 and bitter rot combined, and their attention was turned to an investigation of 

 the disease. 



This disease is well distributed over the eastern half of the Unied States, 

 occurring in some regions to such an extent that fully 50 per cent of the fruit 

 is rendered unfit for packing. 



The disease, which is of a fungus origin, was first described as occurring on 

 the fruit in a bulletin of the Illinois Station (E. S. K., 13, p. 1059) and later 

 its occurrence was noted by a number of investigators. In 1907 the authors 

 pointed out the relation between certain cankers and leaf spots to the blotch 

 on the fruit. About the same time similar observations were reported by Shel- 

 don (E. S. K., 19, p. 348), who identified the fungus as PhiiUo.sticta .solitaria. 



Apple blotch occurs on the fruit, branches, and leaves, the form on the fruit 

 being by far the most important from an economic standpoint. On the fruit, 

 the first evidence of the disease is shown in small, inconspicuous, light brown 

 blotches, which spread rapidly with an irregular, jagged, advancing margin. 

 Where the spots are numerous they often coalesce and form large blotches, 

 which may cover half the apple or more. The fungus kills only the superficial 

 cells, so that continued growth results in the cracking of the fruits. 



Characteristic cankers are formed by the fungus on fruit spurs, twigs, and 

 rapidly growing shoots. At first these cankers are rather small and inconspic- 

 uous, ajipearlng as small purt)le or black blotches. As they increase in size 

 they become brown in the center, retaining a purple margin, but may finally 

 become gray. The Inirk soon cracks around the cankers,^ especially along the 

 lateral edges. 



On the leaves the spots ai-e irregular, light brown, yellowish, or whitish, small, 

 and are of comparatively minor importance. 



The fungus is believed to pass the winter in the twig cankers, these fur- 

 nishing the chief source of infectiim. As in the case of other fungus diseases, 

 the apple blotch is dependent more or less upon weather conditions, although 

 it develops in cool as well as in warm weather. 



A wide range in susceptibility of different varieties of apples to this disease 

 is noted. An account of the life history of the fungus, a description of its cul- 

 tural characters, and the results of inoculation experiments are given. 



It was shown in 1906 that spraying with Bordeaux mixture was successful 

 in i)reventing the disease, and in 1907 the experiments were repeated to deter- 

 mine the number and times of ajtplication. In most of the experiments a 5 : 5 : 50 

 Bordeaux mixture was employed, but it is thought that i)robably a weaker 

 solution or one containing a greater amount of lime might be advantageously 

 employed. For the prevention of codling moth and other insect injuries, the 

 addition of 2 lbs. of arsenate of lead or 6 oz. of Paris green is reeonunended. 



The principal iicriod of infection comes usually from 4 to (! weeks after the 

 petals have la lieu, and 4 applications of Bordeaux mixture, the first .'5 or 4 

 weeks after the iM-tals have fallen, will ordiiuirily be found sufficient. By c*om- 

 biiiing the treatments for insect enemies, bitter rot. blotch, leaf siiot and scab, 

 II applications, the first when the cluster buds are begimiing lo show conspicu- 

 ously and the last about the first of August, would be found advantageous for 

 the control of all of the more imiiortant apple troubles. 



Scaly bark of citrus, II. S. Fawcktt ( ll( r'uUi Sl<i. Hiil. US. i)ii. 7J-.S'rt. /h/s. ,i). — 

 This is ,1 preliminary rei»ort of investigations on scaly bark, which has been 



