Florida Agricultural Experiment Station


in the spring. The trouble may appear suddenly on a few trees
in the grove and speedily develop on a large number of trees,
both young ones and o!d bearing ones. In such cases it is a ques-
tion whether the trouble should be regarded as withertip or as
 merely a natural balancing
 of the top of the tree inev-
 itably following the reduc-
 tion of the root system.
 Outbreaks of withertip
 often follow prolonged high
 winds, even though they
 are not sufficiently severe
 to cause any apparent dam-
 age to the trees. Withertip
 also develops abundantly in
 trees that have been se-
 verely whipped by hurri-
 canes, especially when the
 tissues of the leaves, twigs,
 and branches have been in-
 jured by extreme desicca-
 tion or by the action of salt
 spray. Such injuries, to-
 gether with the numerous
 abrasions and wounds re-
 sulting from winds of hur-
 ricane intensity, afford ex-
 cellent places for the spores
 of the universally present
 withertip fungus to gain
 entrance. Owing to the
 rapid propagation of the
 withertip fungus in weak-
 ened or injured tissues of
 citrus trees, it is difficult to
 distinguish between injury
 initiated by the withertip
 fungus and that initiated
Fig. 38.-Withertip on small lemon by injuries alone, after
 twigs, showing the sharp line of de-
 markation between the dead and liv- which the fungus has in-
 ing wood, and the numerous black vaded the tissues as a sap-
 fruiting bodies developing on the
 dead wood. rophytic or semi-parasitic