Florida Agricultural Experiment Station


mosis can be cured fairly readily in most cases by proper treat-
ment, provided the disease has not progressed beyond the inter-
mediate stages. However, the ease of treatment and likelihood
of cure are decreased greatly when the disease has been allowed
to go unchecked for several years.
 The bark-scraping method recommended for the treatment
of psorosis has been found equally effective for the treatment
of the various forms of gummosis so commonly seen on older
bearing trees in Florida. Since this method of treatment is
so similar for the two diseases, the reader is referred to the sec-
tion on the control of psorosis, where a detailed account of the
treatment is given in connection with the control of that dis-
ease (see page 80). The bark-scraping method here recom-
mended has proved vastly superior to the old method heretofore
used, which consisted merely in scraping off the loose, scaling
bark and masses of exuded gum, cutting out the gumming areas
of bark down to the wood and applying some disinfectant, usual-
ly carbolineum. Aside from its inefficiency and likelihood of in-
juring the trees with the carbolineum, such a method resulted
in unsightly wounds which required years to heal and paved the
way for the entrance of wood-decaying fungi.
 PSOROSIS
 Cause unknown but undoubtedly an organism
 Psorosis* was first described briefly from Florida by Swingle
and Webber in 1896. In 1908 this disease became known in
California under the name "scaly bark." However, this name
is reserved for an entirely different disease in Florida. Psoro-
sis is generally understood by Florida growers, but erroneously
so, to be a form of gummosis. This disease, or a similar one,
has been reported in nearly every important citrus growing
country of the world. The available evidence led Lee to conclude
that psorosis originated in the Orient and has been distributed
to other citrus-growing countries with the spread of Citrus va-
rieties and species.
 Psorosis occurs throughout the citrus-producing section of
Florida, affecting tangerine, orange, and grapefruit trees to a
serious extent. Tangerines are extremely susceptible to psorosis
but seem to withstand the ravages of the disease longer than
 *This name is from the Greek word meaning ulcer. It is pronounced
so-ro'-sis.