Florida Agricultural Experiment Station


 CONTROL OF MUSHROOM ROOT ROT
 It is far easier to take steps to prevent the occurrence of mush-
 room root rot than it is to control the disease after it develops in
 the trees. In clearing timbered land for grove sites, with the
 exception of low hammock land where it would be economically
 impossible, it is highly desirable to remove all roots as thorough-
 ly as is practical and to prepare the land by deep plowing,
 which will bring to the surface roots which have been overlooked
 in clearing. This is especially important where oak trees occur
 on the land.
 Unfortunately, no work has been done in regard to the pos-
 sbility of controlling Clitocybe root rot although more than 125
 citrus trees have been treated recently in Florida to determine
 this point. However, considerable valuable experimental work
 has been done in attempting to control the closely related Armil-
 laria root rot. From the known facts it would appear that there
 is but little hope of saving trees attacked by either of these
 mushroom root rot fungi without careful surgical work and aera-
 tion of the root crowns and crown roots, which calls for rather
 tedious and painstaking work. The mycelium of these root-
 rot fungi is very sensitive to drying out, and the removal of the
 soil from under the bases of the trees so as to leave the root
 crowns and crown roots exposed for aeration and drying has
 proved to be very beneficial in checking the development of these
 root-rot fungi. Considerable experimental work has been done
 in attempting to control Armillaria and other root-rot fungi by
 various chemical treatments of the soil, both in this country and
 abroad, but without sufficiently consistent success to justify any
 recommendations.
 When trees in the grove are attacked by Clitocybe root rot
the control measures will be determined to a large extent by the
local circumstances. Two main problems are presented: (1)
the prevention of the spread of the disease to adjoining unat-
tacked trees and (2) the treatment of the trees already attacked.
Probably the most effective method of preventing the spread
of the disease when the attacked trees occur in a group is to
isolate them by digging a narrow trench of sufficient depth to
extend below all the communicating roots and cutting out all roots
crossing from either side. The dirt removed should be thrown
back on the inside of the area. A depth of from two to three feet
will probably suffice ordinarily under Florida conditions.