INSECTS. 365 



tliick, curled, nnd 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. 



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 cor- 

 roded, 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 Peincipal Insects injurious to Fkuit 



Tkees. 



1. Aphis or Plant-Louse . — There are 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. 

 The apple, pear and cherry, are especially infested with 

 them. They multiply with wonderful rapidity. It is said 

 that one individual in five generations might be the pro- 

 genitor of six thousand millions. Were it not that they 



* Prof. Harris says in his Treatise on Insects, that it is caused by plant- 

 lice puncturing the under sides of the leaves. 



