CHAPTER XIII

INSECTS AND DISEASES AND METHODS OF FIGHTING THEM

I use the term "methods of fighting" rather than the more usual one, "remedies," because by both experience and study I am more and more convinced that so long as the commercial fields of agriculture remain in the present absolutely unorganized condition, and so long as the gardener--home or otherwise--who cares to be neglectful and thus become a breeder of all sorts of plant pests, is allowed so to do--just so long we can achieve no remedy worth the name. When speaking of a remedy in this connection we very frequently are putting the cart before the horse, and refer to some means of prevention. Prevention is not only the best, but often the only cure. This the gardener should always remember.

This subject of plant enemies has not yet received the attention from scientific investigators which other branches of horticulture have, and it is altogether somewhat complicated.

Before taking up the various insects and diseases the following analysis and list will enable the reader to get a general comprehension of the whole matter.

Plant enemies are of two kinds--(1) insects, and (2) diseases. The former are of two kinds, (a) insects which chew or eat the leaves or fruit; (b) insects which suck the juices therefrom. The diseases also are of two kinds--(a) those which result from the attack of some fungus, or germ; (b) those which attack the whole organism of the plant and are termed "constitutional." Concerning these latter practically nothing is known.

It will be seen at once, of course, that the remedy to be used must depend upon the nature of the enemy to be fought. We can therefore reduce the matter to a simple classification, as follows:

PLANT ENEMIES

Insects Class

Eating a Sucking b

Diseases

Parasitical c Constitutional d

REMEDIES

Mechanical Number Covered boxes........... 1 Collars................. 2 Cards................... 3

Destructive Hand-picking............ 4 Kerosene emulsion....... 5 Whale-oil soap.......... 6 Miscible oils........... 7 Tobacco dust............ 8 Carbolic acid emulsion.. 9 Corrosive sublimate.... 10 Bordeaux mixture....... 11

Poisonous Paris green............ 12 Arsenate of lead....... 13 Hellebore.............. 14

It will be of some assistance, particularly as regards quick reference, to give the following table, which shows at a glance the method of fighting any enemy, the presence of which is known or anticipated.

While this may seem quite a formidable list, in practice many of these pests will not appear, and under ordinary circumstances the following six remedies out of those mentioned will suffice to keep them all in check, _if used in time:_ Covered boxes, hand-picking, kerosene emulsion, tobacco dust, Bordeaux mixture, arsenate of lead.

ENEMY | ATTACKING | CLASS | REMEDY --------------------|----------------------------|--------|------- Aphis (Plant-lice) | Cabbage and other plants, | b | 5,8,6 | especially under glass | | Asparagus-beetle | Asparagus | a | 13, 12 Asparagus rust | Asparagus | c | 11 Black-rot | Cabbage and the cabbage | d | 10 | group | | Borers | Squash | b | 4 Caterpillars | Cabbage group | a |12, 14, 4 Caterpillars | Tomato | a | 4 Club-root | Cabbage group | c | see text Cucumber-beetle | Cucumber and vines | a | 1, 11, 8 (Striped beetle) | | | Cucumber-wilt | Cucumber and vines | c | 11 Cucumber-blight | Cucumber, muskmelon, | c | 11 | cabbage | | Cut-worm | Cabbage, tomato, onion | a |2,4,12,13 Flea-beetle | Potato, turnip, radish | a | 11, 5 Potato-beetle | Potato and egg-plant | a |12, 13, 4 Potato-blight | Potato | c | 11 Potato-scab | Potato (tubers) | c | 10 Root-maggot | Radish, onion, cabbage, | a | 4, 3, 9 | melons | | Squash-bug | Squash, pumpkin | b |4,8,12,5 White-fly | Plants; cucumber, tomato | b | 6, 5, 8 White-grub | Plants | a | 4

However, that the home gardener may be prepared to meet any contingency, I shall take up in brief detail the plant enemies mentioned and the remedies suggested.

_Aphis:_--The small, soft green plant-lice. They seldom attack healthy growing plants in the field, but are hard to keep off under glass. If once established it will take several applications to get rid of them. Use kerosene or soap emulsion, or tobacco dust. There are also several trade-marked preparations that are good. Aphine, which may be had of any seed house, has proved very effective in my own work, and it is the pleasantest to use that I have so far found.

_Asparagus-beetle:_--This pest will give little trouble on cleanly cultivated patches. Thorough work with arsenate of lead (1 to 25) will take care of it.

_Black-rot:_--This affects the cabbage group, preventing heading, by falling of the leaves. In clean, thoroughly limed soil, with proper rotations, it is not likely to appear. The seed may be soaked, in cases where the disease has appeared previously, for fifteen minutes in a pint of water in which one of the corrosive sublimate tablets which are sold at drug stores is dissolved.

_Borers:_--This borer is a flattish, white grub, which penetrates the main stem of squash or other vines near the ground and seems to sap the strength of the plant, even when the vines have attained a length of ten feet or more. His presence is first made evident by the wilting of the leaves during the noonday heat. Coal ashes mixed with the manure in the hill, is claimed to be a preventative. Another is to plant some early squash between the hills prepared for the winter crop, and not to plant the latter until as late as possible. The early squash vines, which act as a trap, are pulled and burned.

Last season almost half the vines in one of my pieces were attacked after many of the squashes were large enough to eat. With a little practice I was able to locate the borer's exact position, shown by a spot in the stalk where the flesh was soft, and of a slightly different color. With a thin, sharp knife-blade the vines were carefully slit lengthwise on this spot, the borer extracted and killed and the vines in almost every instance speedily recovered. Another method is to root the vines by heaping moist earth over several of the leaf joints, when the vines have attained sufficient length.

_Cabbage-caterpillar:_--This small green worm, which hatches upon the leaves and in the forming heads of cabbage and other vegetables of the cabbage group, comes from the eggs laid by the common white or yellow butterfly of early spring. Pick off all that are visible, and spray with kerosene emulsion if the heads have not begun to form. If they have, use hellebore instead. The caterpillar or worm of tomatoes is a large green voracious one. Hand-picking is the only remedy.

_Club-root:_--This is a parasitical disease attacking the cabbage group, especially in ground where these crops succeed each other. Lime both soil and seed-bed--at least the fall before planting, unless using a special agricultural lime. The crop infested is sometimes carried through by giving a special dressing of nitrate of soda, guano or other quick-acting powerful fertilizer, and hilled high with moist earth, thus giving a special stimulation and encouraging the formation of new roots. While this does not in any way cure the disease, it helps the crop to withstand its attack. When planting again be sure to use crop rotation and to set plants not grown in infested soil.

_Cucumber-beetle:_--This is the small, black-and-yellow-striped beetle which attacks cucumbers and other vines and, as it multiplies rapidly and does a great deal of damage before the results show, they must be attended to immediately upon appearance. The vine should be protected with screens until they crowd the frames, which should be put in place before the beetles put in an appearance. If the beetles are still in evidence when the vines get so large that the screens must be removed, keep sprayed with Bordeaux mixture. Plaster, or fine ashes, sifted on the vines will also keep them off to some extent, by keeping the leaves covered.

_Cucumber-wilt:_--This condition accompanies the presence of the striped beetle, although supposed not to be directly caused by it. The only remedy is to get rid of the beetles as above, and to collect and burn every wilted leaf or plant.

_Cucumber-blight_ or _Mildew_ is similar to that which attacks muskmelons, the leaves turning yellow, dying in spots and finally drying up altogether. Where there is reason to fear an attack of this disease, or upon the first appearance, spray thoroughly with Bordeaux, 5-5-50, and repeat every ten days or so. The spraying seems to be more effective on cucumbers than on melons.

_Cut-worm:_--The cut-worm is perhaps the most annoying of all garden pests. Others do more damage, but none is so exasperating. He works at night, attacks the strongest, healthiest plants, and is content simply to cut them off, seldom, apparently, eating much or carrying away any of the severed leaves or stems, although occasionally I have found such bits, especially small onion tops, dragged off and partly into the soil. In small gardens the quickest and best remedy is hand-picking. As the worms work at night they may be found with a lantern; or very early in the morning. In daytime by digging about in the soil wherever a cut is found, and by careful search, they can almost invariably be turned out. As a preventive, and a supplement to hand-picking, a poisoned bait should be used. This is made by mixing bran with water until a "mash" is made, to which is added a dusting of Paris green or arsenate of lead, sprayed on thickly and thoroughly worked through the mass. This is distributed in small amounts--a tablespoonful or so to a place along the row or near each hill or plant--just as they are coming up or set out. Still another method, where only a few plants are put out, is to protect each by a collar of tin or tar paper.

_Flea-beetle:_--This small, black or striped hard-shelled mite attacks potatoes and young cabbage, radish and turnip plants. It is controlled by spraying with kerosene emulsion or Bordeaux.

_Potato-beetle:_--The striped Colorado beetle, which invariably finds the potato patch, no matter how small or isolated. Paris green, dry or sprayed, is the standard remedy. Arsenate of lead is now largely used. On small plots hand-picking of old bugs and destruction of eggs (which are laid on under side of leaves) is quick and sure.

_Potato-blight:_--Both early and late forms of blight are prevented by Bordeaux, 5-5-50, sprayed every two weeks. Begin early-- when plants are about six inches high.

_Potato-scab:_--Plant on new ground; soak the seed in solution prepared as directed under No. 10, which see; allow no treated tubers to touch bags, boxes, bins or soil where untreated ones have been kept.

_Root-maggot:_--This is a small white grub, often causing serious injury to radishes, onions and the cabbage group. Liming the soil and rotation are the best preventives. Destroy all infested plants, being sure to get the maggots when pulling them up. The remaining plants should be treated with a gill of strong caustic lime water, or solution of muriate of potash poured about the root of each plant, first removing an inch or so of earth. In place of these solutions carbolic acid emulsion is sometimes used; or eight to ten drops of bisulphide of carbon are dropped into a hole made near the roots with the dibber and then covered in. Extra stimulation, as directed for _Club-root_, will help carry the plants through.

_Squash-bug:_--This is the large, black, flat "stink-bug," so destructive of squash and the other running vines. Protection with frames, or hand-picking, are the best home garden remedies. The old bugs may be trapped under boards and by early vines. The young bugs, or "sap-sucking nymphs," are the ones that do the real damage. Heavy tobacco dusting, or kerosene emulsion will kill them.

_White-Fly:_--This is the most troublesome under glass, where it is controlled by fumigation, but occasionally is troublesome on plants and tomato and cucumber vines. The young are scab-like insects and do the real damage. Spray with kerosene emulsion or whale-oil soap.

_White-grub_ or _muck-worm:_--When lawns are infested the sod must be taken up, the grubs destroyed and new sward made. When the roots of single plants are attacked, dig out, destroy the grubs and, if the plant is not too much injured, reset.

The remedies given in the table above are prepared as follows:

MECHANICAL REMEDIES

1.--_Covered boxes:_--These are usually made of half-inch stuff, about eight inches high and covered with mosquito netting, wire or "protecting cloth"--the latter having the extra advantage of holding warmth over night.

2.--_Collars_ are made of old cans with the bottoms removed, cardboard or tarred paper, large enough to go over the plant and an inch or so into the ground.

3.--_Cards_ are cut and fitted close around the stem and for an inch or so upon the ground around it, to prevent maggots going down the stem to the root. Not much used.

DESTRUCTIVE REMEDIES

4.--_Hand-picking_ is usually very effective, and if performed as follows, not very disagreeable: Fasten a small tin can securely to a wooden handle and fill one-third full of water and kerosene; make a small wooden paddle, with one straight edge and a rather sharp point; by using this in the right hand and the pan in the left, the bugs may be quickly knocked off. Be sure to destroy all eggs when hand-picking is used.

5.--_Kerosene emulsion_ is used in varying strengths; for method of preparing, see Chapter XVII.

6 and 7.--For use of whale-oil soap and miscible oils, see Chapter XVII.

8.--_Tobacco dust:_--This article varies greatly. Most sorts are next to worthless, but a few of the brands especially prepared for this work (and sold usually at $3 per hundred pounds, which will last two ordinary home gardens a whole season) are very convenient to use, and effective. Apply with a duster, like that described in Implements.

9.--_Carbolic acid emulsion:_--1 pint crude acid, 1 lb. soap and 1 gal. water. Dissolve the soap in hot water, add balance of water and pump into an emulsion, as described for kerosene emulsion.

10.--_Corrosive sublimate_ is used to destroy scab on potatoes for seed by dissolving 1 oz. in 7 gals, of water. The same result is obtained by soaking for thirty minutes in a solution of commercial formalin, at the rate of 1 gill to 15 gals. of water.

11.--_Bordeaux mixture:_--See Chapter XVII.

POISONOUS REMEDIES

12.--_Paris green:_--This is the standard remedy for eating-bugs and worms. With a modern dusting machine it can be put on dry, early in the morning when the dew is still on. Sometimes it is mixed with plaster. For tender plants easily burned by the pure powder, and where dusting is not convenient, it is mixed with water at the rate of 1 lb. to 50 to 100 gals. and used as a spray. In mixing, make a paste of equal quantities of the powder and quicklime, and then mix thoroughly in the water. It must be kept stirred up when using.

13.--_Arsenate of lead:_--This has two advantages over Paris green: It will not burn the foliage and it will stay on several times as long. Use from 4 to 10 lbs. in 100 gals. of water; mix well and strain before putting in sprayer. See also Chapter XVII.

14.--_Hellebore:_--A dry, white powder, used in place of Nos. 12 or 13 on vegetables or fruit that is soon to be eaten. For dusting, use 1 lb. hellebore to 5 of plaster or flour. For watering or spraying, at rate of 1 lb. to 12 gals. of water.

PRECAUTIONS

So much for what we can do in actual hand-to-hand, or rather hand-to- mouth, conflict with the enemy. Very few remedies have ever proved entirely successful, especially on crops covering any considerable area. It will be far better, far easier and far more effective to use the following means of precaution against plant pest ravages: First, aim to have soil, food and plants that will produce a rapid, robust growth without check. Such plants are seldom attacked by any plant disease, and the foliage does not seem to be so tempting to eating- insects; besides which, of course, the plants are much better able to withstand their attack if they do come. Second, give clean, frequent culture and keep the soil busy. Do not have old weeds and refuse lying around for insects and eggs to be sheltered by. Burn all leaves, stems and other refuse from plants that have been diseased. Do not let the ground lie idle, but by continuous cropping keep the bugs, caterpillars and eggs constantly rooted out and exposed to their natural enemies. Third, practice crop rotation. This is of special importance where any root disease is developed. Fourth, watch closely and constantly for the first appearance of trouble. The old adages "eternal vigilance is the price of peace," and "a stitch in time saves nine," are nowhere more applicable than to this matter. And last, and of extreme importance, be prepared to act _at once_. Do not give the enemy an hour's rest after his presence is discovered. In almost every case it is only by having time to multiply, that damage amounting to anything will be done.

If you will keep on hand, ready for instant use, a good hand-sprayer and a modern powder gun, a few covered boxes, tobacco dust, arsenate of lead and materials for kerosene emulsion and Bordeaux mixture, and are not afraid to resort to hand-picking when necessary, you will be able to cope with all the plant enemies you are likely to encounter. The slight expense necessary--considering that the two implements mentioned will last for years with a little care--will pay as handsome a dividend as any garden investment you can make.