Florida Agricultural Experiment Station


than on any definite knowledge of the cause of the disease.
Broadly considered, there are two general methods for preven-
tion or control, namely, correcting the soil conditions and cul-
tural practices which seem to induce the development of the dis-
ease and the treatment with bluestone (copper sulphate). These
methods of treatment are often used together.
 Correcting the Soil Conditions and Cultural Practices:-The
 matter of prime importance is to ascertain, if possible, the soil
 condition or cultural practice which induced its development, to
 correct this, and provide the trees with the proper conditions for
 making normal growth. It usually requires at least one to two
 years for the average tree that is not chronically affected to en-
 tirely recover. The symptoms that have developed on the twigs
 and branches cannot be removed by treatment but a further
 development of the disease on the succeeding growth can be
 prevented. Badly injured and stunted trees should be replaced
 with new ones. Cutting out the affected branches before the
 abnormal condition is corrected seems merely to aggravate the
 trouble.
 Where exanthema is induced by excessive cultivation, this
operation should be reduced as much as is consistent with con-
serving the soil moisture by keeping down the growth of weeds,
using only implements of shallow tillage. In some cases, it may
be advisable to do this by mowing. Any grass, weeds, or legum-
inous cover crops that are mowed should be left to rot on the
ground without being turned under, or used as a mulch about
the trees. While it has long been the general practice to reduce
the amount of nitrogenous fertilizer applied to trees affected by
exanthema, it is apparent in many cases that increased applica-
tions of nitrogen aid in the correction of this trouble. In ap-
plying fertilizer, especially when it is not harrowed in, care
should be taken to secure even distribution.
 Groves subject to great fluctuations of soil moisture should
be handled so as to minimize as much as possible the tendency
for the soil to become extremely dry or wet. Where exanthema
occurs on poorly drained land, little can be expected from any
method of treatment until adequate drainage is provided. Ditch-
ing or breaking up the hardpan layer with light charges of dyna-
mite will help materially in providing the necessary drainage
where water tends to collect locally. Frequently, raising and
mounding the trees will prove helpful.