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.

=======================================================================
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.
=======================================================================

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.