AMERICAN HOME GARDEN. 261 



LEAF-BLIGHT. 



What is called leaf-blight in the pear, plum, etc., seems to 

 be merely the result of a check given to the growth by heat 

 or other cause, just as the hawthorn, refusing to acclimate 

 well, annually loses its foliage in the summer or early fall, 

 and becomes unsightly. It may be avoided in some measure, 

 if not entirely, in fruit-trees, by good culture upon deep soils, 

 moderately dry. 



MILDEW. 



Mildew is an appearance of mouldiness upon the young 

 growth. Among fruit-trees it prevails upon some varieties of 

 peach and nectarine, and upon grape-vines of foreign kinds. 

 It generally follows a check in the growth by sudden change 

 of temperature, etc., which is accompanied by numbers of a 

 small aphis that punctures the back of the leaf and sucks the 

 diseased juices ; almost immediately the mildew proper ap- 

 pears, which seems to be a very minute vegetable growth. 



It is removable by syringing or showering with a solution 

 of an ounce of nitre to a gallon of water, with soap-suds, or 

 lime-water, or any alkaline solution, or dusting with sulphur ; 

 but in respect to foreign vines can only be effectually met by re- 

 newing them every three or four years, either by layering from 

 their own young shoots, or by young plants from other sources. 



SOUR-SAP BLIGHT. 



This disease is also called " fire blight," from the appear- 

 ance of the tree destroyed by it ; " frozen-sap blight," from 

 the theory of its being the effect of frost upon the chemical 

 condition of the sap in overgorged vessels, and by European 

 cultivators the " canker," and is described by them as result- 

 ing from the sap being " corrupted by putrid water (i. e., in 

 the subsoil) or excess of manure," and as working like a gan- 

 grene on the parts affected. 



It is a disease of surfeit or plethora, often appearing in the 

 pith near the points of very vigorous offshoots. 



The change in the sap, from whatever cause it may proceed, 



