432 F. M. Rolfs 



invasion of the roots by one of the root rot organisms. The trees of this 

 orchard were uneven and produced very httle fruit. 



In the same year another tract of about one hundred acres of new land 

 was planted with two-years-old Elbert a trees brought from the same 

 nursery. In this case the ground had been thoroughly prepared and 

 the orchard was carefully cultivated during the following three years. 

 A number of infected trees were observed in different parts of this orchard 

 in the first year, but the disease spread very little and by the end of the 

 third year all traces of disease had disappeared. The trees developed 

 uniformly and produced large crops of excellent, clean fruit. 



Diseased trees that have been properly cultivated invariably hold 

 their leaves longer and resist the influence of the organism much better 

 than do poorly cultivated trees. The general vigor of the host plays an 

 important part in controlling the disease. Trees standing in thin, poor 

 soil invariably suffer more severely than do those standing in more fertile 

 places. Trees that yield abundantly are less resistant than those that 

 produce little or no fruit. The foliage of infected trees that yield full 

 crops in two consecutive years usually falls prematurely if the trees are 

 not liberally fertilized and well cultivated. 



In the spring of 1907 the peach trees in the Missouri State Fruit Experi- 

 ment Station variety orchard were cut back severely, and about the 

 middle of May complete fertilizer at the rate of 800 pounds to the acre 

 was applied to the soil on one-half of the orchard. The same amount was 

 applied also to an acre of Elberta peach trees of the same age which had 

 not been cut back. Both the variety orchard and the Elberta orchard 

 were finally planted in cowpeas. On September 1 the foliage on the trees 

 that had been cut back and fertilized was in good condition and no pre- 

 mature defoliation was observed. The foliage on the Elberta trees, 

 which had been fertilized and not cut back, was in fair condition, but 

 from two to five per cent of the leaves had fallen. The foliage of the trees 

 that had been cut back and not fertilized was more or less injured and 

 from ten to twenty per cent of the leaves had fallen. The most striking 

 results, however, appeared in September, 1908. The trees in the fertilized 

 and cut-back block were practically free from disease. The foliage on 

 the Elberta trees, which had been fertilized and not cut back, was more or 

 less diseased, twenty per cent of the leaves had fallen, and many of the 

 twigs contained black cankers. The foliage on the block of trees which 



