-8- 



Symptoms on Peach : 



Diseased trees appear normal and cannot be distinguished from healthy trees 

 for the first 6 or 8 weeks after growth starts. The leaves are normal and so are 

 the flowers. About mid- June, leaves on branches scattered throughout the tree, 

 or on only one or t\<ro branches, start to turn yellow, develop yellow-red blotches, 

 become brittle, and, on many, spots fall out leaving a ragged tattered leaf. 

 Some leaves may roll longitudinally with the edges rolled upward, and others may 

 be distorted or twisted. Often normal leaves are interspersed with the diseased 

 leaves. 



Up to this point, the sjrmptoms are similar to those caused by any one of 

 several conditions. But with X- Disease the leaves drop, beginning at the base 

 of the twig and progressing toward the tip, until finally there remains only a 

 tuft of undersized green or yellowish leaves at the tip. 



The immature fruit on severely diseased branches drop soon after leaf 

 symptoms appear. Fruit on less severely diseased branches may grow to maturity 

 but are undersized, ripen prematurely, have poorly developed pits, and an insipid 

 slightly bitter taste. Branches with normal leaves and no disease symptoms pro- 

 duce normal fruit. 



Diseased bearing trees leaf out normally in spring and may live for many 

 years but become commercially worthless in 2 to 4 years after becoming diseased. 

 Seedling trees 3 years old or less may be killed before they reach bearing age. 



Symptoms on Chokecher ry : 



The change in leaf color begins about the same time as on peach - i.e. 6 

 to 7 weeks after growth starts in spring or about mid- June. Newly infected choke- 

 cherries start off with dull green or yellowish leaves which become brilliant 

 yellow, orange or red by August. Often the midrib remains green. The second and 

 third year after infection the leaves are less brilliantly colored and even dull. 

 Tufts or rosettes of small stunted leaves develop on the ends of the branches some 

 of which die and eventually the whole plant dies. 



Transmission ; 



The disease has been transmitted from peach to peach, peach to chokecherry, 

 chokecherry to peach and chokecherry to chokecherry. Transmission has been 

 successful with buds, bark patches, and grafts but not with plant juice. 



The disease first appears in an orchard near the edges, near diseased choke- 

 cherries. It may spread to other trees in an orchard at the rate of 20% of the 

 trees in one year. How does it pass from chokecherry to peach and from peach to 

 peach in an orchard so rapidly? No one really knows. Certainly there is no 

 budding or grafting of diseased chokecherries onto commercial peaches and no 

 grafting from peach to peach in an established orchard. It is believed that 

 insects may be the carriers and there is some evidence to support this view. In 

 experiments, the virus has been successfully transmitted to healthy plants by at 

 least one leaf hopper. 



