470 INSECTS AFFECTING VEGETATION 



rough on the outside and dark colored beneath the surface. Some 

 injury of this sort appears to be connected with the disease described 

 above, the bark dying in certain spots rather than in a strip up and 

 down the whole length of the branch or trunk. True pear blight 

 may also cause a similar effect by running in from a small shoot or 

 fruit spur, but many cases of both black leaf and crater blight occur 

 without the presence of the pear blight organism. Frequently, what 

 is called crater blight is really nothing more than the normal rough- 

 ening of the bark of the pear tree as it grows older. In this tree the 

 bark begins to crack and roughen in patches on the trunk and main 

 limbs, and its normal condition has sometimes the appearance of the 

 outbreak of some disease. 



Curly Bark. This is somewhat similar to the above, the bark 

 cracking in concentric rings in spots upon the surface of the main 

 limbs. It is not of any serious consequence. 



Fruit Drop. The young fruit drops from the tree while still 

 very small and immature. Due to imperfect pollination. Ordina- 

 rily results simply in a desirable thinning of the fruit, but sometimes 

 a large part of the crop drops from this cause. May also be produced 

 by frost affecting the fruit soon after setting. Such fruit may re- 

 main on the tree and continue to grow for some time after the frost 

 occurs before falling. 



Ringed Fruit. Some years many pears are found at maturity 

 with a scabby ring or belt of considerable width extending around 

 the fruit. The pears are constricted in this portion, owing to inter- 

 ference with the growth. It is evident that this effect comes about 

 through some injury to the pear when it is quite young. This is a 

 frost effect, and pears in a very small, young condition may be seen 

 with similar rings about them in a season when much damage has 

 been caused by late frost. 



Bitter Rot (See page 457) ; Powdery Mildew (See page 

 457) ; Leaf Spot (See page 455) ; Black Rot (See page 459). 



DRUPACEOUS FRUIT DISEASES. 



DISEASES OF ALMONDS. 



Shoi-Hole. There appear on the leaves numerous small, dead 

 spots, which finally fall out, giving a shot-hole effect. The young 

 twigs are also spotted. The trees are sometimes defoliated early in 

 the season by this fungus and the crop badly injured. Spray with 

 Bordeaux mixture in the spring as the buds are opening. 



Rust. Red or brown,, dusty pustules appear on the under side 

 of the leaves, usually late in the season. The fungus may hasten the 

 normal dropping of the leaves somewhat but is not serious on thrifty 

 trees ; worse where the trees suffer from drouth. No treatment ordi- 

 narily needed. 



Root Rot Oak Fungus. Many orchards of almonds and other 

 trees contain certain spots where the trees commence dying from a 

 center, the trouble gradually proceeding outward in a circle, involv- 

 ing tree after tree. Clusters of toadstools frequently appear about 

 the base of affected trees in the winter. These spots usually coin- 



