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: weather, soil, orchard management and parasites. 
