454 DISEASES AND INSECTS. 



these warts not even an inch of any branch free from 

 them, the most disgusting objects in the way of fruit 

 trees that can possibly be imagined. 



The Curl of the Leaf in the Peach. This disease causes 

 the leaves to assume a reddish color, to become thick, 

 curled, and deformed, and finally to perish. It is supposed 

 by many to be caused by insects ; but it is really induced 

 by a sudden change of weather. In proof of this we may 

 adduce the fact that peach-trees under glass are never 

 affected with this disease; and the more sheltered the 

 position is, the less is the injury. 



A number of warm days, that cause the expansion of 

 the young leaves, followed by a cold rainy day, is almost 

 sure to produce it to some extent; and the more severe 

 and protracted the cold, the more, extensive and fatal it is. 

 The peach-trees in Western New York suffered more from 

 this in 1849-50 than in the ten years previous, owing to a 

 protracted cold time in each season after the young tender 

 leaves had expanded. In both these seasons the check was 

 so severe, as not only to produce this disease in its worst 

 form, but the gum also ; for the sap not being absorbed 

 by the leaves, became stagnant, sour, and corroded, and 

 burst the bark. Trees in sheltered gardens suffer less than 

 those in exposed orchards. There is no possible way of 

 guarding against this ; and the only remedy known to us 

 is, to pick off the diseased leaves the moment the weather 

 changes, that new healthy ones may be produced. 



SECTION 2. THE PRINCIPAL INSECTS INJURIOUS TO 

 FRUIT TREES. 



Aphis or Plant-Louse. There arc several kinds of 

 these. The two most troublesome to fruit trees are the 

 green and black, small soft insects that appear suddenly 

 in immense quantities on the young shoots of the trees, 

 suck their juices, and consequently arrest their growth. 



