Bulletin 140, Dieback of Citrus Trees


much difference between its prevalence in these and in those
budded on the sweet, grapefruit and sour stocks. On the other
hand, it is much less prevalent in trees budded on the slow-grow-
ing trifoliata stock.
 It is stated by growers that the Ruby Blood orange budded on
 the rough lemon stock is particularly susceptible to the disease.
 SYMPTOMS OF CITRUS DIEBACK
 Dieback affects the terminal and subterminal branches, the



 Al













 FIG. 2.-Dieback in young trees on spruce pineland

leaves and the fruit. It seldom affects the larger branches or the
trunk except in severe cases in young trees. The roots of se-
verely affected trees often show a lack of fibrous roots and
feeding tips. In some cases, brownish, discolored and injured
roots are found. On the other hand, the root system of less se-
verely affected trees may show.no injury whatever.
 The name given this disease is misapplied. It suggests that
the dying of the limbs is a distinguishing characteristic. Such
is not the case. The disease does not manifest itself by a mere
dying back of the outer branches, as in the case of withertip. The
death of the limbs is an after effect, and occurs only in severe
cases. The distinguishing characteristic of dieback is the gum
symptoms.
 PRIMARY SYMPTOMS
 Dieback is a gum disease of citrus trees. In the absence of