Evening star., 1948-04-18

Among the few unpleasant chores
every successful gardener must
undertake is the control OF insect
pests and fungus or bacterial dis
eases. The task seems even more
difficult when one realizes that doz-
ems of different kinds of insects and
other parasites are capable of at
tacking each kind Of plant. But the
Job will not be half as formidable If
one endeayors to learn something
about the nature Of plant pests and
of the materials used to combat
them.
Insect Control Problems.
Let us first consider the problem
of insect control The type of spray
to use is determined by the kind OF
injury the insect does, that is,
whether the plants are chewed up
or whether the plant juices are
sucked out. If the insect is biting
off the leaves or other plant parts,
leaving ragged edges, holes or is
"skeletonizing" the leaves, then
so-called stomach poison, such as
arsenate of lead or DOT, should be
used. Among the common insects
that chew plants are japanese
beetles, elm leaf beetles, flea beetles,
rose slugs, and tent caterpillar
worms. On the other hand, if there
is no evidence Of actual chewing,
one is reasonably safe in concluding
that a sucking insect is involved
In such cases, contact insecticlde
such as nicotine sulfate, rotenone,
or summer oils are most effective.
Nicotine sulfate is perhaps the most
commonly used contact insecticlde.
The standard strength is prepared
by adding two teaspoonfuls to one
gallon of water in which enough
mild soap flakes have been dis
solved to make a sudsy mixture. :
DDT can be used also for many
sucking insects, for it acts as con-
tact insecticide as well as stomach
poison. Some of the sucking insects
against which this material is Ell
fective are tarnished plant bugs,
lace. bugs, boxwood leaf miner.
chrysanthemum midge, the young
stages of mealy bugs and scales,
some leafhoppers and few species
of aphids. DOT sprays have one
drawback. Constant use OF such
materials on some plants may lead
to a heavy infestation OF red spider
mites. Roses and hemlocks sprayed
repeatedly with DOT, for example,
may suddenly become infested by
large numbers of these tiny pests.
In order to avoid this suitation, one
can include three teaspoonfuls OF
50 per cent hexaethyl tetraphos-
phate (HETP) in each three gallons
of diluted DDT spray. More re-
Gently the material known as BIC
(Benzene hexachloride) has proved
to be excellent for controlling sew
eral kinds of sucking insects, partic-
ularly aphids, white flies and thrips.
Disease Control.
Admittedly the diagnosis OF dis
eases and their control is more dlffl-
cult than is the case with insects.
One reason for this Is that the
gardener cannot see the agents
(fungi, bacteria or viruses) that
cause diseases. All that one sees is
the end result such as leaf spotting
or blighting, stem rotting and stunt
ing. BY the time these symptoms
are visible, it is usually too late to do
anything about 1t. Hence the con-
troll of plant diseases rests largely
on preventing their getting started.
There are several practices every
good gardener undertakes to ward
off diseases. The first requisite for
keeping plants healthy is to provide
good soil drainage. Another way to
avoid diseases is to practice garden
sanitation. While it is possible for
the spores of fungi and bacteria to
be blown or carried in water for
some distance, the fact is that most
Of these parasitic fungi and bacteria
in gardens live over on plant parts
which were infected the previous
year. Hence it is extremely i'm
portant that all above ground parts
of nerennia1s and/ fallen leaves be