Evening star., 1933-08-13
SOIL DISEASES.

Not all plant diseases attack tne 1oAl
age and other above-ground parts OF
the plant. Some OF the more serious
are those which lie hidden in the SOIL,
and the first manifestation is often the
sudden whiting of the plants. followed
by their death. The home garden, win
its continuous culture year after year,
offers an ideal situation for sou-m-
habiting diseases to increase ana, al
though good sanitation, such as the
gathering and burning of old stalks ana
other rubbish aids materially, trouble
cannot always be averted.
There are several forms OF disease
that may at times become troublesome
and, since the manifestations on the
plant itself are much the same, 1t Is
difficult to identify the various causes.
Aster wilt is trouble Of this class with
which many home gardeners are ia
miliar SnapdragonS appear also to be
rather susceptible to Soil-borne para
sites.
Favorable conditions for the disease
are, unfortunately, those most favor
able for the plant Many different
species of ANIMALS and pe1ennials are
susceptible to injury from soil patho-
gems. Unlike above ground diseases by
the time injury is manifest 1t is usually
too late to accomplish any control.
Al lSoAASe AooaSA ~
the United States Department of Agrl-
culture Dr. Freeman Weiss discusses
control measures for oil-inhabiting
diseases. Some of the troubles are
brought to the garden in or on seed.
Aster wilt is a notable example, and
the precaution of treating the seed for
one-haf hour in a 1,O00-to-1 solution
of mercury bichloride would prevent
the introduction of the organism into
the garden soil.
Garden soil once infested with dis
ease organisms can be restored to pro-
ductive condition by treatment with
heat or with chemicals. For the home
gardener, heating is generally out of
the question because of cost of equip
ment Among chemicals. formalde-
hyde is the most practicable agent, but
even this is too potent for living plants.
The leaflet states lone must either
forego planting the treated area for
period varying from several days to
several months. or else the quantity of
chemical must be reduced so that it
will be harmless or only slightly inimical
to the favored plants. even though
some of the fungicidal efficiency IS
sacrificed.
1T is generally preferable to clear
the plot temporarily of all plants one
wishes to save, thus permitting rela-
lively drastic disinfection. then let the
area rest for about two weeks after
treatment before replantlng.
Beds that are to be treated with
chemical should be spaded to a depth
of to II inches, stones should be re-
moved, and the larger Jumps of soil
broken up. If supply of potting soil
Is to be treated it should be spread out
to a depth of inches and sprinkled
with the solution until thoroughly wet;
1t Is then covered with another layer
of soil, which is similarly treated, and
so on Enough solution must be used
to penetrate the soil thoroughly.
"Of course, a soil with a large pro-
portion Of clay or humus will require
more solution than sandy one even
though the rate Of absorption IS slower.
Ordinarily to 4 quarts of liquid per
square foot will be required. The appli-
cation Is most conveniently made with
q garden sprinkling can. As soon after
applying LIQUID treatment as the soil
has dried sufficiently to handle with
out impairing its texture, it should be
stirred thoroughly at intervals of sew
eral days to promote aeration and dry
ing. II dry fungicide has been ap-
piled to bench or ground bed. the
soil should be watered repeatedly to
leach out the chemical, and then be
allowed to dry before replanting.
1T should be noted that complete
sterilization Is not the aim of soil disin-
lection and is seldom attained by either
heat or chemical processes. Sometimes
it Is necessary only to shift the balance
between the host and its parasites, so
that the former will prosper and the
latter are more or less suppressed.
Fertilizers may act to prevent or allevi-
ate diseases by increasing the vigor Of
the host plants.
"One gallon Of formalin should be
added to 49 gallons of water; the solu-
ton should be applied at rate ap-
proximating two quarts per square foot.
The labor of applying the solution may
be lessened by making up stronger
solution of formalin-e. g., one gallon to
or 10 gallons of water-which is ap-
piled with sprinkling can, after which
the plot Is thoroughly drenched from a
hose
1T Is advisable to cover the treated
soil with burlap, canvas or mating for
one or two days, in order to retain the
volatile gas and increase the fungicidal
action Treated soil should not be
planted until the odor of formaldehyde
has disappeared.
"Formaldehyde is very poisonous to
green plants and should not be applied
even in high dilutions to soil containing
living plants, although only slight and
transitory injury is suffered if the soil
is sprinkled with a solution not over
one-fourth of per cent Il pint for
malin In 80 gallons Of water).'