456 INSECTS AFFECTING VEGETATION 



diseased condition causes the leaves to drop prematurely, frequently 

 leaving the trees denuded in early autumn, six weeks or two months 

 before the normal period of leaf fall. Trees thus deprived of their 

 foliage cease activity, and as a result the fruit is small and not prop- 

 erly matured; the buds for the crop of the following year are weak- 

 ened and in some cases not fully developed, and the life of the tree 

 is materially shortened. These leaf diseases are partly responsible 

 for the failure of the trees to produce crops and for the early decline 

 of the orchard. (F. B. 283.) 



Leaf spots are due to several different fungi, perhaps the most 

 prominent of which is a species of Phyllosticta. A species of Hen- 

 dersonia and the ordinary black-rot fungus, Sphseropsis malorum, 

 are found in connection with some of these spots and may be respon- 

 sible for the injury in some cases. Other fungi are also frequently 

 present in the dead areas, and it is not always clear which are the 

 real parasites. 



One of the most striking results of spraying an apple orchard is 

 the effect on the foliage. These leaf diseases are largely prevented by 

 applications of Bordeaux mixture, and the foliage remains fresh and 

 green long after unsprayed trees are defoliated. This was true of all 

 the demonstration blocks in the Ozarks during the past season. The 

 unsprayed trees began to shed their leaves in July and were practically 

 defoliated by the last of August, a month before the time to pick 

 the crop. 



The treatment recommended for bitter-rot and apple blotch will 

 largely prevent these leaf troubles and hold the foliage in good condi- 

 tion until frost. It is true that some of the leaves become affected 

 soon after they unfold in the spring, but the trouble does not usually 

 become serious before midsummer, and the four applications of Bor- 

 deaux mixture for bitter-rot at intervals of two to three weeks, begin- 

 ning about six weeks after the blossoms are shed, appear to give rea- 

 sonable protection. However, the earlier applications usually neces- 

 sary for the control of apple scab and the codling moth aid in the 

 control of leaf-spot diseases, and when these are made, only one or 

 two of the later sprayings are necessary. \Vhen it is desired to spray 

 for leaf-spot diseases only, the first application should be made about 

 two or three weeks after the petals have fallen, and a second about 

 seven weeks later. These two applications, if thoroughly made, will 

 usually hold the foliage in good condition. 



Brown Spot, Frog Eye. From a commercial standpoint this dis- 

 ease is more injurious to the foliage of the apple than either the blight 

 or scab fungus. The attacks of this enemy are entirely confined to 

 the foliage of the tree. But its work is none the less to be dreaded 

 on that account, for anything which lessens or interferes with the 

 leaves or their functions affects the most vital portion of the plant. 



When seriously affected the trees appear as though the leaves 

 had been parched and blanched by the sun, but close inspection shows 

 that the diseased areas are more or less localized and that the first indi- 

 cations of the disease are small brownish red spots which gradually 

 enlarge, the center becoming lighter in color, and finally two or more 



