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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.