PRESS BULLETIN No. 292
UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
SUMMER FALLOW FOR ROOT-KNOT-INFESTED LAND
J. R. WATSON
Our sandy lands after being cultivated for a year or two
usually become infested with the organism which causes root-
knot. This is a minute round worm related to the hook worm
and the "eel" found in mother of vinegar. This worm bores into
the roots of many'kinds of plants, including nearly all truck crops,
and causes them to produce large swellings along the roots until
the latter look like badly knotted ropes. Some plants, like sun-
flowers and mulberry trees, are able to make more or less satis-
factory growth in spite of the worms. Others, like okra, figs,
tomatoes and cucumbers, are quickly killed or so badly stunted
as to be worthless. Infested plants fail to grow or to bear fruit
properly, turn yellow and finally die.
Home garden patches because of their continuous planting
to susceptible crops suffer most from the root-knot nematode. It
is their most destructive pest.
METHODS OF CONTROL
There are three practical methods of dealing with root-knot:
(1) Plant the land for three consecutive years to crops on
which the worms do not thrive and so starve them out. For a
list of resistant plants send for Bulletin 136, Florida Agricul-
tural Experiment Station. This is the best method to use under
general farming conditions. But the man with only a small
kitchen garden or the trucker with a small area of expensive irri-
gated land can hardly afford to use this method.
(2) Treat the land with some chemical which will kill the
worms. At the Florida Agricultural Experiment Station "Cyan-
amid" (see Bulletin 136, Fla. Ag. Exp. Sta.) and a double treat-
ment of sodium cyanide and ammonium sulphate have been used
successfully. Altho expensive they are at the same time valuable
July 20, 1918
nitrogenous fertilizers. But, due to the demands of the munition
factories, both cyanamid and ammonium sulphate are now off
(3) Summer fallowing of the land. Experiments carried
on during the past year at the Florida Agricultural Experiment
Station show that a thoro fallow during one summer will prac-
tically exterminate the worms in the soil.
The land was deeply plowed and then cultivated at least
once each week and after each rain so as to prevent the growth
of absolutely any vegetation and to prevent the formation of a
crust which would keep the air out of the soil.
HEAT, MOISTURE AND AIR ESSENTIAL
Like most organisms, nematodes require for their growth
in addition to food, a sufficient amount of heat, moisture and air.
If the necessary amount of any of these is lacking the worms may
go into a resting state in which they form around themselves a
thick, heavy coat called a "cyst." In this state they can remain
alive but inactive for many months. But if all conditions are
favorable, the cysts and eggs must hatch. If there is no food
available the worms will soon die. During the summer in Florida
the constant high temperature and heavy rainfall are very fav-
orable to the growth of the worms. But unless the surface of
the soil is frequently stirred there is apt to be a lack of sufficient
air in the soil and some of the worms may remain in the cysts.
In a small kitchen garden, chickens may be given the run of
the land while it is in fallow. They will add fertilizer to the
soil and help to maintain the dust mulch, but the cultivation of
the land must not be neglected.
The fallowing should be started early, not later than July,
and kept up until the land is planted in the fall.
State papers please copy.