Bulletin 229, Diseases of Citrus in Florida


other preparations that exclude the air retard it. Carbolineums
are not recommended for the treatment of either psorosis or
gummosis because of their variable nature and the tendency of
some to be injurious. None of those tried have proved to be
any more effective than a number of much cheaper preparations,
such as lime-sulphur pastes and washes or bordeaux paste, all
of which are much easier to obtain and are perfectly safe to use.
Within a period of from three to six months from the date of
treatment, depending upon the fungicide used and the kind of
tree, the vigor of the tree and the time of the year it was treated,
the outer corky portion of the scraped bark will crack loose and
slough off, exposing the new and usually healthy bark. Bark
treated during the spring months appears to recover most
rapidly.
 All trees treated for either gummosis or psorosis should be
inspected at intervals of a few months, especially during late
spring and early summer, when these bark diseases develop most
rapidly. In case the bark was not scraped sufficiently far in
advance of the disease to check its development or if new in-
fections develop, an additional area should be scraped and treated
as before. Growers cannot expect an infallible cure in advanced
cases of either gummosis or psorosis by a single treatment, since
a second and sometimes even a third, supplementary treatment
may be required. In order to be effective, the method of treat-
ment recommended must be administered carefully, thoroughly,
and intelligently. The importance of scraping the bark well
in advance of the margins of the lesions and of the follow-up
treatments where the development of the disease has not been
checked cannot be too strongly emphasized.
 Tools-A number of different types of scraping implements
may be used for scraping bark attacked by psorosis or gummosis.
The most important feature of such tools, in addition to con-
venience and efficiency for the work, is that they have a sharp
scraping edge. A box scraper and a farrier's knife have been
found to be the most useful implements thus far tried. The
former is excellent for heavy work; the latter, with the end
curved slightly, is fine for work in crotches and for gouging out
small diseased areas or gum pockets in the bark. The box
scraper comprises a reversible, triangular-edged scraper mounted
in a handle with a slightly curved shank. If desired, one or more
of the corners of the scraping blade may be ground off round