Florida Agricultural Experiment Station


gum manifestations, the disease cannot be recognized. There
is a possibility that the disease exists in citrus trees without pro-
ducing gum symptoms, but no means is known at present for
identifying it as such with certainty.
 The symptoms of the disease with which the production of
gum in the tissues is associated, are the gum pockets, the bark
excrescences, the stained terminal branches, the marked or am-
moniated fruit, and the multiple buds. Of these, the bark ex-
crescences, the stained terminal branches, and the marked fruit
are the ones that are characteristic of the disease. When any of
these symptoms are found, the disease may be suspected or can
be identified with certainty. The gum pockets and the multiple
buds are not entirely characteristic of the disease. Gum pockets
that are not exactly the same, but are very similar, are produced
in the immature branches by the sting of plant bugs. However,
where the gum pockets occur regularly one to a node, they in-
dicate dieback. Multiple buds have been found accompanying
some severe cases of frenching, but there are indications that
these may be cases of dieback with an absence of the gum
symptoms.
 Dieback is a disease of the growing tissues. Mature tissues
 are not affected by it. It reaches its greatest development in
 rapidly growing trees. It is less likely to develop in slow or
 normal growing trees. Each of the gum symptoms is confined
 to particular plant parts, and is coincident in development with
 certain stages of growth of these parts. The symptoms which
 will be produced in the tree by the disease stimulus are entirely
 dependent upon the stage and condition of growth of the plant
 parts.
 Gum Pockets.-The gum pockets develop in the young suc-
 culent terminal branches before they have attained full length
 growth. They never develop anew in mature branches. Early
 stages of their development may occur in connection with each
 of the other primary symptoms. They consist of pockets of a
 pure, clear or amber colored gum between the wood and bark at
 or near the leaf nodes. In the formation of a pocket, the bark
 above is raised giving a gross appearance similar to that of a
 large blister. (Fig. 3.)
 The gum pockets never kill a branch. As the stem grows
 older, new wood is formed over the pocket, burying it. It finally
 disappears.
 Bark Excrescences.-The bark excrescences develop in the