Bulletin 229, Diseases of Citrus in Florida


areas of considerable size. New bark often forms under the old
as the latter cracks off and only rarely do dead areas on the
trunks or large limbs result from this disease. Where the dis-
ease has been of several years' standing, the branches often
exhibit band-like lesions encircling them, which closely resemble
psorosis.


 Fig. 36.-Nail-head rust spots on orange.
 In cross sections of old diseased branches on which the bark
has become quite rough and scaly, lines of gum canals, identical
with those shown for psorosis, in Fig. 31, are invariably found in
the outer layers of the wood. These occur intermittently in the
wood tissue formed after the start of the disease. They may
be either partly or entirely continuous around the stem and may
be repeated at varying intervals. In badly diseased branches,
new bark sometimes forms under the old as the latter sloughs