Inserts and Diseases. 161 



only instances where the remedy has failed, is where it has been but 

 occasionally applied, or where the disease has been suffered to 

 spread for a time unchecked. The only way is to cut and continue 

 cutting, so long as any traces remain. As a general but not univer- 

 sal rule, the yellow plums are not so liable to excrescences as 

 purple varieties, unless surrounded by diseased trees. 



The leaf-blight, or premature casting of the foliage, proves in 

 some seasons a serious disaster to the plum, as it checks the growth 

 of the shoots, and prevents the ripening of the fruit. Occasionally 

 it has been so severe as to spoil entirely the value of the crop. 



The leaf -blight of the pear proves a formidable obstacle in raising 

 pear seedlings, attacking the leaves often by midsummer, and caus- 

 ing an immediate suspension of growth. No satisfactory remedy 

 has been discovered the best preventive is a deep, rich soil, and 

 good cultivation to produce strong growth. This disease is evi- 

 dently caused by a minute parasitic fungus ; and a similar fungus 

 attacks the leaves and fruit of larger trees, producing the disaster 

 known as cracking of the fruit. Some varieties are more' liable to 

 crack than others ; and while in certain localities it renders them 

 worthless, in others they entirely escape. In some instances the 

 disease has gradually extended over certain varieties from one dis- 

 trict of country to another. No remedy has yet been found. 



The Yellows. The disease termed the Yellows is truly formida- 

 ble. It is peculiar to the peach and nectarine. It has destroyed 

 whole orchards in portions of the country, and for a time induced 

 the entire abandonment of the peach culture in certain localities. 



The cause of this malady has not been satisfactorily ascertained. 

 According to conjecture, it has arisen originally from exhaustion by 

 deteriorated soil, overbearing, and neglected pruning and bad culti- 

 vation. But whatever may have been its origin, it appears at pre- 

 sent to be chiefly communicated from diseased trees. It is quickly 

 induced by inserting the bud from an affected tree into a healthy 

 stock. It spreads by contact with diseased roots ; a knife used in 

 pruning the tree will infuse the poison if used on another. It 

 appears to be communicated without actual contact, the healthy 

 branches nearest a diseased tree being usually first attacked. It is 

 also probable that the stones from diseased trees cause its develop- 

 ment after a few years' growth. Its highly contagious nature, when 

 in its most virulent form, is indicated by the equal facility with 

 which young and vigorous trees, and old and feeble, may be inocu- 

 lated by contact. 



Its infallible indications are, first, a premature ripening of tht 



