286 MANUAL OF FRUIT DISEASES 



yellows certain characteristic symptoms are exhibited. (1) Ab- 

 normal dwarfed shoots may appear on the trunks or limbs ; 

 but, as already noted, these may develop during the first year. 

 (2) Affected trees may be barren after the first year, or they 

 may bear another crop of fruit which ripens prematurely as 

 described for the first year. (3) Affected trees may die the 

 second year, but ordinarily they succumb slowly from the top 

 downward (Fig. 77). When the first symptoms of yellows 

 appear in any part of a tree, it is thought that the whole tree 

 is then diseased. 



The true yellows of peach should never be confused with 

 little-leaf or California-yellows. This disease is characterized 

 by the development of spindling, yellow shoots on the new 

 growth with small, narrow, yellow leaves. The foliage along 

 such shoots drops prematurely, leaving tufts at the ends. The 

 fruit fails to develop; it shrivels and finally falls. It is a 

 trouble peculiar to trees from three to seven years of age, whereas 

 true yellows affects older orchard trees. 



Cause of yellows. 



Just what causes peach-yellows is still unknown. It there- 

 fore falls into a class, from the causal standpoint at least, with 

 rosette and little-peach. The cause of yellows has aroused 

 much speculation because of the importance of the disease and 

 on account of its obscure nature. Many theories have been 

 advanced to explain the origin of the peculiar symptoms ex- 

 hibited by diseased trees, but all of these have been certainly 

 disproved. Some of the prominent theories regarding the cause 

 of peach-yellows follow : (1) severe winter-injury ; (2) exces- 

 sive rainfall; (3) impoverished soil, that is, a deficiency in 

 lime, potash and phosphoric-acid ; (4) insects ; (5) fungi ; 

 (6) bacteria ; (7) crowding trees in the orchard ; (8) excessive 

 cultivation; (9) over-bearing. Many others might be added. 

 It will be seen that these fall into one or the other of the cate- 

 gories : w r eather, soil, orchard management and parasites. 



