HOUSE-PLANT INSECTS AND DISEASES
If the suggestions for taking proper care of plants, detailed in a
former chapter, are carefully followed, and they are given plenty of
fresh air and not crowded together, insects should not cause serious
trouble.
No matter how careful one may be, however, they are almost certain to
put in an appearance and steps to combat them must be taken immediately.
Remember, however, that the best remedy is prevention, and the best
prevention is to have good strong healthy plants.
The two troubles perhaps the most common are neither insects nor
disease. They are gas and sour soil.
The faintest trace of furnace gas or of illuminating gas will cause
trouble, indicated by the yellowing and falling of the leaves and
unsatisfactory development of buds. Where there is no way of eliminating
the presence of these gases the only way to success with the
plants--unless they can be entirely shut off in an enclosed place as
suggested in Chapter II--is to take every possible care about leaks, and
to give all the fresh air possible.
Sour soil is the result of improper drainage conditions, too much
water, or both. It causes the leaves to turn yellow and checks new
growth. Making right the harmful conditions will usually renew the
health of the plant, but in bad cases it will be far better to remove
the earth, wash the soil from the roots, carefully clean the pot--if the
same one is to be used--and repot in good porous fresh earth. Keep on
the dry side until growth is resumed.
As a rule, insects do much more damage to house plants than is caused by
diseases. One characteristic of nearly all plant insects which will
astonish the amateur is the marvelous rapidity with which they increase.
One to-day, and to-morrow a million, seems no exaggeration. While it may
be true that, as one of our erstwhile best-selling heroes said, "a few
fleas is a good thing for a dog; they keep him from broodin' on bein' a
dog," a few bugs are certainly not good for a plant, because in a day or
two there will be enough of them to endanger its life and surely,
quickly to ruin its appearance. Never let the bugs get a start. If you
take them in time they're easy: if not you have a very difficult and
disagreeable task on your hands.
PLANT ENEMIES
_Aphis._ Aphis or green plant louse is the most commonly encountered of
all the insect pests. It used to be dreaded, but with modern methods it
may be readily and effectively exterminated. There are several forms and
colors of these pests. If you have attempted plant-growing you are
undoubtedly familiar with them. In the house, shaded places, crowded
plants, poor ventilation, dry plants, all furnish environment favorable
to the development of aphids. Change these conditions at once. The old
method of fighting used to be by burning moistened tobacco stems, or
steeping them in water and making a very weak tea for spraying. But
either was a difficult, disagreeable and unsatisfactory method. There
are now on the market three forms of tobacco all of which are easy to
use and efficient. Tobacco dust--but it must be strong and made
especially for the purpose; liquid nicotine, to be diluted and sprayed
on according to directions; and prepared paper for fumigating. The last
is perhaps the most effective. Besides these, and in my experience
pleasanter and quicker, is the comparatively new compound called Aphine,
which can be had from almost any seedsman in quart tins--enough to make
five gallons of very effective spray, which will not discolor flowers or
foliage.
_Red Spider._ This very serious pest is about the size and color of a
grain of red pepper--although sometimes appearing brown or dull red. To
make himself inconspicuous, he works on the under side of the leaves and
behind a tiny web, but his presence is soon made manifest by the leaves
upon which he is at work, which first turn light green, then show
minute yellow spots, turn yellow and finally drop off.
The red spider is very tenacious of life, and hard to get rid of when he
is allowed time to become well established. The best weapon to use
against him, where it can be done, is clear cold water with as much
force as possible against the under side of the foliage. Damp atmosphere
assists in the work; so keep the air damp, and be on a sharp lookout.
Evaporated sulphur, or flowers of sulphur dusted upon the leaves will
also help.
Where the collection of plants is not too large a one, the quickest and
most certain way to be rid of the spider is to dip the top of each plant
quickly two or three times into hot water--140 to 165 degrees. Although
uncomfortable to the hand, water of this temperature will not injure the
tenderest plant. It is effective against aphis and mealy bug, as well as
against the spider.
_Mealy Bug._ The mealy bug inhabits a white, cottony looking mass, which
is easily seen. Remove this covering and the real intruder is there. It
is most fond of the soft-wooded plants, such as coleus and fuchsias,
thrives in a hot, dry atmosphere, and will keep out of sight, if not
watched for, in a mass of leaves or under some branch axis, until there
are a large number.
If they are discovered before multiplying to any great extent,
exterminate them with a fine brush or feather dipped in alcohol,
coal-oil or kerosene, any of which, if applied directly to them, will
kill them on the spot.
_Scale._ The scales infesting house plants are of two kinds. The more
common is the brown scale, which has a hard, slightly convex, circular
shell, one-quarter of an inch or so in diameter. The white scale is much
smaller, and soon forms quite dense colonies. Both attack the
thick-leaved, smooth-barked plants, such as palms, ferns, lemons, and
abutilons. They do not appear to be doing any damage, but invisibly suck
the juices of the plant. They should be destroyed at once. This is
accomplished by the use of fir-tree-oil soap, whale-oil soap, or
kerosene emulsion and a stiff brush.
_Thrips._ These do not often appear in the house, but may where plants
are crowded in a shady place. They eat the substance of the leaves,
leaving only the skeleton structure. They are small, about a quarter of
an inch long, and brown or black. Aphine, kerosene emulsion or Paris
green (one teaspoonful to twelve quarts of water) will keep them quiet.
_Root Aphis._ Sometimes the leaves of a healthy plant will begin to look
sickly with no apparent cause. It may be found upon examination that the
blue root aphis is at work, clinging in clusters to the rootlets. Remove
and wash away the soil, and then wash the roots in whale-oil soap suds,
and repot in fresh soil. If no fresh soil is available, tobacco tea or
tobacco dust should be washed into the soil every other day for a week.
_Soil Worms._ The common earthworms sometimes find their way into a pot,
and while they do not seem to bother the roots, I should judge from
observation that they render the soil next to useless, especially in
small pots. Another worm, or rather larva, sometimes to be found, is
very small and hatches into a small white fly. If numerous, they do a
good deal of damage. The treatment recommended for root aphis will get
rid of them; or lime water (slake a piece of fresh lime the size of an
apple in a pail of water, drawing off the water after settling), if used
freely will kill them.
DISEASES
There are but two plant diseases likely to attack plants in the house:
fungus and mildew. The first seems to be a sort of decomposition of the
leaf, leaving a black, powdery residue. It is combated by spraying with
bordeaux. Bordeaux can now be had in paste or powder form, which for
small quantities is much better than to try to mix it yourself.
Mildew causes the tenderest leaves to curl up and some of them seem to
be covered with a white powder. Flowers of sulphur, dusted over the
plants while the foliage is damp, is the standard remedy.
For the sake of ready reference, the foregoing is condensed in the
following simple table of plant insects and diseases.
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INSECT | CONDITIONS |
OR | SUPPORTING | REMEDIES
DISEASE | GROWTH |
-------------------+----------------------+----------------------------
Aphis, green and | Shade; poor | Aphine; tobacco-dust
black | ventilation; | or tea; kerosene
| thick foliage | emulsion; hot
| | water bath; insect
| | powder.
| |
Aphis, blue | Stunted growth; | Whale-oil soap
| lack of water | solution; repotting;
| | tobacco tea applied to
| | roots.
| |
Thrips, 1/4 inch, | Shaded places; | Kerosene emulsion;
long, brown or | crowded plants | Paris green--1
black; they eat. | | teaspoon to 12 quarts
Mealy bugs } | | water.
Other scale } | Corners; close, | Brush off; coal-oil;
insects } | dry air | kerosene emulsion;
| | hot water.
| |
Red spider | Hot, dry | Moisture, sulphur,
| atmosphere | hot water.
| |
Rose-beetle | | Hand picking; wood
| | ashes.
| |
White flies | Dry foliage | Kerosene emulsion.
(Aleyrodes) | |
| |
| |
Slugs | Dark corners; | Air-slaked lime.
| dampness; | sweetened bran and
| decaying wood | Paris green.
| |
Ants | | Insect powder;
| | molasses traps.
| |
Angleworms | Dampness; heavy | Lime; lime-water;
| soil | tobacco tea, and
| | tobacco dust washed
| | into soil.
| |
| |
White grub | Manure not old |
| enough. Destroy. |
| |
Fungous leaf spot | Shocks; checks | Bordeaux; Fungine.
| |
Mildew | Checks | Flowers of sulphur;
| | Fungine.
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To make the kerosene emulsion, use 2 ounces of soap (whale-oil is much
better than the common), 1 quart of boiling water (over brisk fire), 2
quarts of kerosene oil. Dissolve the soap in boiling water, remove from
fire, and add oil. Churn or beat until of the consistency of cream. If
correctly mixed, the emulsion, on cooling, will adhere without oiliness
to glass. Use rain water, if possible; if not, add a little baking soda
to the water.
For scale insects, dilute with 10 parts of water; for aphis and soft
insects, with 15 or 20 parts water. In using kerosene emulsion, apply in
fine spray. Remember it must come in contact with the insect to be
effective.