PROTECTING PLANTS FROM THINGS THAT PREY ON THEM
Plants are preyed on by insects and fungi; and they are subject to
various kinds of disease that, for the most part, are not yet
understood. They are often injured also by mice and rabbits (p. 144),
by moles, dogs, cats, and chickens; and fruit is eaten by birds. Moles
may be troublesome on sandy land; they heave the ground by their
burrowing and may often be killed by stamping when the burrow is being
raised; there are mole traps that are more or less successful. Dogs and
cats work injury mostly by walking across newly made gardens or lying
in them. These animals, as well as chickens, should be kept within
their proper place (p. 160); or if they roam at will, the garden must
be inclosed in a tight wire fence or the beds protected by brush laid
closely over them.
The insects and diseases that attack garden plants are legion; and yet,
for the most part, they are not very difficult to combat if one is
timely and thorough in his operations. These difficulties may be
divided into three great categories: the injuries wrought by insects;
the injuries of parasitic fungi; the various types of so-called
constitutional diseases, some of which are caused by germs or bacteria,
and many of which have not yet been worked out by investigators.
[Illustration: Fig. 211. Shot-hole disease of plum.] [Illustration:
Fig. 212. Hollyhock rust.]
The diseases caused by parasitic fungi are usually distinguished by
distinct marks, spots or blisters on the leaves or stems, and the
gradual weakening or death of the part; and, in many cases, the leaves
drop bodily. For the most part, these spots on the leaves or stems
sooner or later exhibit a mildew-like or rusty appearance, due to the
development of the spores or fruiting bodies. Fig. 211 illustrates the
ravages of one of the parasitic fungi, the shot-hole fungus of the
plum. Each spot probably represents a distinct attack of the fungus,
and in this particular disease these injured parts of tissue are liable
to fall out, leaving holes in the leaf. Plum leaves that are attacked
early in the season by this disease usually drop prematurely; but
sometimes the leaves persist, being riddled by holes at the close of
the season. Fig. 212 is the rust of the hollyhock. In this case the
pustules of the fungus are very definite on the under side of the leaf.
The blisters of leaf-curl are shown in Fig. 213. The ragged work of
apple scab fungus is shown in Fig. 214.
[Illustration: Fig. 213. Leaf-curl of peach, due to a fungus.]
The constitutional and bacterial diseases usually affect the whole
plant, or at least large portions of it; and the seat of attack is
commonly not so much in the individual leaves as in the stems, the
sources of food supply being thereby cut off from the foliage. The
symptoms of this class of diseases are general weakening of plant when
the disease affects the plant as a whole or when it attacks large
branches; or sometimes the leaves shrivel and die about the edges or in
large irregular discolored spots, but without the distinct pustular
marks of the parasitic fungi. There is a general tendency for the
foliage on plants affected with such diseases to shrivel and to hang on
the stem for a time. One of the best illustrations of this type of
disease is the pear-blight. Sometimes the plant gives rise to abnormal
growths, as in the “willow shoots” of peaches affected with yellows
(Fig. 215).
[Illustration: Fig. 214. Leaves and fruits injured by fungi, chiefly
apple-scab.]
Another class of diseases are the root-galls. They are of various
kinds. The root-gall of raspberries, crown-gall of peaches, apples, and
other trees, is the most popularly recognized of this class of troubles
(Fig. 216). It has long been known as a disease of nursery stock. Many
states have laws against the sale of trees showing this disease. Its
cause was unknown, until in 1907 Smith and Townsend, of the Bureau of
Plant Industry, United States Department of Agriculture, undertook an
investigation. They proved that it is a bacterial disease (caused by
_Bacterium tumefaciens_); but just how the bacteria gain entrance to
the root is not known. The same bacterium may cause galls on the stems
of other plants, as, for example, on certain of the daisies. The
“hairy-root” of apples, and certain galls that often appear on the
limbs of large apple-trees, are also known to be caused by this same
bacterium. The disease seems to be most serious and destructive on the
raspberry, particularly the Cuthbert variety. The best thing to be done
when the raspberry patch becomes infested is to root out the plants and
destroy them, planting a new patch with clean stock on land that has
not grown berries for some time. Notwithstanding the laws that have
been made against the distribution of root-gall from nurseries, the
evidence seems to show that it is not a serious disease of apples or
peaches, at least not in the northeastern United States. It is not
determined how far it may injure such trees.
[Illustration: Fig. 215. The slender tufted growth indicating peach
yellows. The cause of this disease is undetermined.]
[Illustration: Fig. 216. Gall on a raspberry root.] [Illustration: Fig.
217. Canker-worm.]
Of obvious insect injuries, there are two general types,—those wrought
by insects that bite or chew their food, as the ordinary beetles and
worms, and those wrought by insects that puncture the surface of the
plant and derive their food by sucking the juices, as scale-insects and
plant-lice. The canker-worm (Fig. 217) is a notable example of the
former class; and many of these insects may be dispatched by the
application of poison to the parts that they eat. It is apparent,
however, that insects which suck the juice of the plant are not
poisoned by any liquid that may be applied to the surface. They may be
killed by various materials that act upon them externally, as the soap
washes, miscible oils, kerosene emulsions, lime-and-sulfur sprays, and
the like.
There has been much activity in recent years in the identification and
study of insects, fungi, and microorganisms that injure plants; and
great numbers of bulletins and monographs have been published; and yet
the gardener who has tried assiduously to follow these investigations
is likely to go to his garden any morning and find troubles that he
cannot identify and which perhaps even an investigator himself might
not understand. It is important, therefore, that the gardener inform
himself not only on particular kinds of insects and diseases, but that
he develop a resourcefulness of his own. He should be able to do
something, even if he does not know a complete remedy or specific. Some
of the procedure, preventive and remedial, that needs always to be
considered, is as follows:—
Keep the place clean, and free from infection. Next to keeping the
plants vigorous and strong, this is the first and best means of
averting trouble from insects and fungi. Rubbish and all places in
which the insects can hibernate and the fungi can propagate should be
done away with. All fallen leaves from plants that have been attacked
by fungi should be raked up and burned, and in the fall all diseased
wood should be cut out and destroyed. It is important that diseased
plants are not thrown on the manure heap, to be distributed through the
garden the following season.
Practice a rotation or alternation of crops (p. 114). Some of the
diseases remain in the soil and attack the plant year after year.
Whenever any crop shows signs of root disease, or soil disease, it is
particularly important that another crop be grown on the place.
[Illustration: Fig. 218. A garden hand syringe.] [Illustration: Fig.
219. A knapsack pump.]
See that the disease or insect is not bred on weeds or other plants
that are botanically related to the crop you grow. If the wild mallow,
or plant known to children as “cheeses” _(Malva rotundifolia_), is
destroyed, there will be much less difficulty with hollyhock rust. Do
not let the cabbage club-root disease breed on wild turnips and other
mustards, or black-knot on plum sprouts and wild cherries, or
tent-caterpillars on wild cherries and other trees.
Always be ready to resort to hand-picking. We have grown so accustomed
to killing insects by other means that we have almost forgotten that
hand-picking is often the surest and sometimes even the most
expeditious means of checking an invasion in a home garden. Many
insects can be jarred off early in the morning. Egg-masses on leaves
and stems may be removed. Cutworms may be dug out. Diseased leaves may
be picked off and burned; this will do much to combat the hollyhock
rust, aster rust, and other infections.
[Illustration: Fig. 220 A compressed-air hand pump for garden work.]
[Illustration: Fig. 221 A bucket pump.]
[Illustration: Fig. 222 A bucket pump.]
[Illustration: Fig. 223 A cart-mounted pump.]
Keep close watch on the plants, and be prepared to strike quickly. It
should be a matter of pride to a gardener to have in his workhouse a
supply of the common insecticides and fungicides (Paris green or
arsenate of lead, some of the tobacco preparations, white hellebore,
whale-oil soap, bordeaux mixture, flowers of sulfur, carbonate of
Copper for solution in ammonia), and also a good hand syringe (Fig.
218), a knapsack pump (Figs. 219, 220), a bucket pump (Figs. 221, 222),
a hand bellows or powder gun, perhaps a barrow outfit (Figs. 223, 224,
225), and if the plantation is large enough, some kind of a force pump
(Figs. 226, 227, 228). If one is always ready, there is little danger
from any insect or disease that is controllable by spraying.
[Illustration: Fig. 224. A garden outfit.]
[Illustration: Fig. 225. A cart-mounted barrel pump.]
[Illustration: Fig. 226. A barrel hand pump.]
[Illustration: Fig. 227. A barrel outfit, showing nozzles on extension
rods for trees.] [Illustration: Fig. 228. A truck-mounted barrel hand
spray Pump.]
_Screens and covers_.
[Illustration: Fig. 229. Wire-covered box for protecting plants from
insects.]
There are various ways of keeping insects away from plants. One of the
best is to cover the plants with fine mosquito-netting or to grow them
in hand-frames, or to use a wire-covered box like that shown in Fig.
229. In growing plants under such covers, care must be taken that the
plants are not kept too close or confined; and in cases in which the
insects hibernate in the soil, these boxes, by keeping the soil warm,
may cause the insects to hatch all the sooner. In most cases, however,
these covers are very efficient, especially for keeping the striped
bugs off young plants of melons and cucumbers.
[Illustration: Fig. 230 Protecting from cut-worms.]
Cut-worms may be kept away from plants by placing sheets of tin or of
heavy glazed paper about the stem of the plant, as shown in Fig. 230.
Climbing cut-worms are kept off young trees by the means shown in Fig.
231. Or a roll of cotton may be placed about the trunk of the tree, a
string being tied on the lower edge of the roll and the upper edge of
the cotton turned down like the top of a boot; the insects cannot crawl
over this obstruction (p. 203).
The maggots that attack the roots of cabbages and cauliflowers may be
kept from the plant by pieces of tarred paper, which are placed close
about the stem upon the surface of the ground. Fig. 232 illustrates a
hexagon of paper, and also shows a tool used for cutting it. This means
of preventing the attacks of the cabbage maggot is described in detail
by the late Professor Goff (for another method of controlling cabbage
maggot see p. 201):—
[Illustration: Fig. 231 Protecting trees from cut-worms.]
“The cards are cut in a hexagonal form, in order better to economize
the material, and a thinner grade of tarred paper than the ordinary
roofing felt is used, as it is not only cheaper, but being more
flexible, the cards made from it are more readily placed about the
plant without being torn. The blade of the tool, which should be made
by an expert blacksmith, is formed from a band of steel, bent in the
form of a half hexagon, and then taking an acute angle, reaches nearly
to the center, as shown in Fig. 232. The part making the star-shaped
cut is formed from a separate piece of steel, so attached to the handle
as to make a close joint with the blade. The latter is beveled from the
outside all round, so that by removing the part making the star-shaped
cut, the edge may be ground on a grindstone. It is important that the
angles in the blade be made perfect, and that its outline represents an
exact half hexagon. To use the tool, place the tarred paper on the end
of a section of a log or piece of timber and first cut the lower edge
into notches, as indicated at _a_, Fig. 232, using only one angle of
the tool. Then commence at the left side and place the blade as
indicated by the dotted lines, and strike at the end of the handle with
a light mallet, and a complete card is made. Continue in this manner
across the paper. The first cut of every alternate course will make an
imperfect card, and the last cut in any course may be imperfect, but
the other cuts will make perfect cards if the tool is correctly made,
and properly used. The cards should be placed about the plants at the
time of transplanting. To place the card, bend it slightly to open the
slit, then slip it on to the center, the stem entering the slit, after
which spread the card out flat, and press the points formed by the
star-shaped cut snugly around the stem.”
[Illustration: Fig. 232 Showing how paper is cut for protecting
cabbages from maggots. The Goff device.]
_Fumigating_.
An effective means of destroying insects in glass houses is by
fumigating with various kinds of smoke or vapors. The best material to
use for general purposes is some form of tobacco or tobacco compounds.
The old method of fumigating with tobacco is to burn slowly slightly
dampened tobacco stems in a kettle or scuttle, allowing the house to be
filled with the pungent smoke. Lately, however, fluid extracts and
other preparations of tobacco have been brought into use, and these are
so effective that the tobacco-stem method is becoming obsolete. The use
of hydrocyanic acid gas in greenhouses is now coming to be common, for
plant-lice, white-fly, and other insects. It is also used to fumigate
nursery stock for San José scale, and mills and dwellings for such
pests and vermin as become established in them. The following
directions are from Cornell Bulletin 252 (from which the formulas in
the succeeding pages, and most of the advice, are also taken):—
“No general formula can be given for fumigating the different kinds of
plants grown in greenhouses, as the species and varieties differ
greatly in their ability to withstand the effects of the gas. Ferns and
roses are very susceptible to injury, and fumigation if attempted at
all should be performed with great caution. Fumigation will not kill
insect eggs and thus must be repeated when the new brood appears.
Fumigate only at night when there is no wind. Have the house as dry as
possible and the temperature as near 60° as practicable.
“Hydrocyanic acid gas is a deadly poison, and the greatest care is
required in its use. Always use 98 to 100 per cent pure potassium
cyanide and a good grade of commercial sulfuric acid. The chemicals are
always combined in the following proportion: Potassium cyanide, 1 oz.;
sulfuric acid, 2 fluid oz.; water, 4 fluid oz. Always use an earthen
dish, _pour in the water first_, and add the sulfuric acid to it. Put
the required amount of cyanide in a thin paper bag and when all is
ready, drop it into the liquid and leave the room immediately. For
mills and dwellings, use 1 oz. of cyanide for every 100 cu. ft. of
space. Make the doors and windows as tight as possible by pasting
strips of paper over the cracks. Remove the silverware and food, and if
brass and nickel work cannot be removed, cover with vaseline. Place the
proper amount of the acid and water for every room in 2-gal. jars. Use
two or more in large rooms or halls. Weigh out the potassium cyanide in
paper bags, and place them near the jars. When all is ready, drop the
cyanide into the jars, beginning on the top floors, since the fumes are
lighter than air. In large buildings, it is frequently necessary to
suspend the bags of cyanide over the jars by cords running through
screw eyes and all leading to a place near the door. By cutting all the
cords at once the cyanide will be lowered into the jars and the
operator may escape without injury. Let the fumigation continue all
night, locking all outside doors and placing danger signs on the
house.”
In greenhouses, the white-fly on cucumbers and tomatoes may be killed
by overnight fumigation with 1 oz. of potassium cyanide to every 1000
cu. ft. of space; or with a kerosene emulsion spray or whale-oil soap,
on plants not injured by these materials.
The green aphis is dispatched in houses by fumigation with any of the
tobacco preparations; on violets, by fumigation with 1/2 to 3/4 oz.
potassium cyanide for every 1000 cu. ft. of space, leaving the gas in
from 1/2 to 1 hr.
The black aphis is more difficult to kill than the green aphis, but may
be controlled by the same methods thoroughly used.
_Soaking tubers and seeds_.
Potato scab may be prevented, so far as planting infected “seed” is
concerned, by soaking the seed tubers for half an hour in 30 gal. of
water containing 1 pt. of commercial (about 40 per cent) formalin. Oats
and wheat, when attacked by certain kinds of smut, may be rendered safe
to sow by soaking for ten minutes in a similar solution. It is probable
that some other tubers and seeds can be similarly treated with good
results.
Potatoes may also be soaked (for scab) one and one-half hours in a
solution of corrosive sublimate, 1 oz. to 7 gal. of water.
_Spraying_.
The most effective means of destroying insects and fungi however, in
any general or large way, is by the use of various sprays. The two
general types of insecticides have already been mentioned—those that
kill by poisoning, and those that kill by destroying the body of the
insect. Of the former, there are three materials in common use—Paris
green, arsenate of lead, and hellebore. Of the latter, the most usual
at present are kerosene emulsion, miscible oils, and the lime-sulfur
wash.
Sprays for fungi usually depend for their efficiency on some form of
copper or sulfur, or both. For surface mildews, as grape mildew,
dusting flowers of sulfur on the foliage is a protection. In most
cases, however, it is necessary to apply materials in liquid form,
because they can be more thoroughly and economically distributed, and
they adhere to the foliage better. The best general fungicide is the
bordeaux mixture. It is generally, however, not advisable to use the
bordeaux mixture on ornamental plants, because it discolors the foliage
and makes the plants look very untidy. In such cases it is best to use
the ammoniacal copper solution, which leaves no stain.
In all spraying operations it is especially important that the
applications be made the very moment the insect or disease is
discovered, or in the case of fungous diseases, if one is expecting an
attack, it is well to make an application of bordeaux mixture even
before the disease appears. When the fungus once gets inside the plant
tissue, it is very difficult to destroy it, inasmuch as fungicides act
on these deep-seated fungi very largely by preventing their fruiting
and their further spread on the surface of the leaf. For ordinary
conditions, from two to four sprayings are necessary to dispatch the
enemy. In spraying for insects in home gardens, it is often advisable
to make a second application the day following the first one in order
to destroy the remaining insects before they recover from the first
treatment.
[Illustration: Fig. 233. Cyclone or vermorel type of nozzle, single and
multiple.]
There are many kinds of machines and devices for the application of
sprays to plants. For a few individual specimens, the spray may be
applied with a whisk, or with a common garden syringe. If one has a few
trees to treat, however, it is best to have some kind of bucket pump
like those shown in Figs. 221, 222. On a lawn or in a small garden a
tank on wheels (Figs. 223, 224, 225) is handy and efficient. In such
cases, or even for larger areas, some of the knapsack pumps (Figs. 219,
220) are very desirable. These machines are always serviceable, because
the operator stands so near to his work; but as they carry a
comparatively small quantity of liquid and do not throw it rapidly,
they are expensive when much work is to be done. Yet, in ordinary home
grounds, the knapsack pump or compressed-air pump is one of the most
efficient and practicable of all the spraying devices.
For large areas, as for small orchards and fields, a barrel pump
mounted on a wagon is best. Common types of barrel pumps are shown in
Figs. 226, 227, 228. Commercial plantations are now sprayed by power
machines. There are many good patterns of spraying machines, and the
intending purchaser should send for catalogues to the various
manufacturers. The addresses may be found in the advertising pages of
rural papers.
As to nozzles for spraying it may be said that there is no one pattern
that is best for all purposes. For most uses in home grounds the
cyclone or vermorel type (Fig. 233) will give best satisfaction. The
pump manufacturers supply special nozzles for their machines.
_Insecticide spraying formulas_.
The two classes of insecticides are here described,—the poisons
(arsenites and white hellebore) for chewing insects, as the beetles and
all kinds of worms; the contact insecticides, as kerosene, oils, soap,
tobacco, lime-sulfur, for plant-lice, scale, and insects in such
position that the material cannot be fed to them (as maggots in the
underground parts).
_Paris green_.—The standard insecticidal poison. This is used in
varying strengths, depending on the insect to be controlled and the
kind of plant treated. Mix the Paris green into a paste and then add to
the water. Keep the mixture thoroughly agitated while spraying. If for
use on fruit trees, add 1 lb. of quick lime for every pound of Paris
green to prevent burning the foliage. For potatoes it is frequently
used alone, but it is much safer to use the lime. Paris green and
bordeaux mixture may be combined without lessening the value of either,
and the caustic action of the arsenic is prevented. The proportion of
the poison to use is given under the various insects discussed in the
succeeding pages.
_Arsenate of lead_.—This can be applied in a stronger mixture than
other arsenical poisons without injuring the foliage. It is, therefore,
much used against beetles and other insects that are hard to poison, as
elm-leaf beetle and canker-worm. It comes in the form of a paste and
should be mixed thoroughly with a small quantity of water before
placing in the sprayer, else the nozzles will clog. Arsenate of lead
and bordeaux mixture can be combined without lessening the value of
either. It is used in strengths varying from 4 to 10 lb. per 100 gal.,
depending on the kind of insect to be killed.
Arsenite of soda and arsenite of lime are sometimes used with bordeaux
mixture.
_White Hellebore_.—For wet application, use fresh white hellebore, 4
oz.; water, 2 or 3 gal. For dry application, use hellebore, 1 lb.;
flour or air-slaked lime, 5 lb. This is a white, yellowish powder made
from the roots of the white hellebore plant. It loses its strength
after a time and should be used fresh. It is used as a substitute for
the arsenical poisons on plants or fruits soon to be eaten, as on
currants and gooseberries for the currant-worm.
_Tobacco_.—This is a valuable insecticide and is used in several forms.
As a _dust_ it is used extensively in greenhouses for plant-lice, and
in nurseries and about apple trees for the woolly aphis. Tobacco
_decoction_ is made by steeping or soaking the stems in water. It is
often used as a spray against plant-lice. Tobacco in the form of
_extracts_, _punks_, and _powders_ is sold under various trade names
for use in fumigating greenhouses. (See page 188.)
_Kerosene emulsion_.—Hard, soft, or whale-oil soap, 1/2 lb.; water, 1
gal.; kerosene, 2 gal. Dissolve the soap in hot water; remove from the
fire and while still hot add the kerosene. Pump the liquid back into
itself for five or ten minutes or until it becomes a creamy mass. If
properly made, the oil will not separate out on cooling.
For use on dormant trees, dilute with 5 to 7 parts of water. For
killing plant-lice on foliage dilute with 10 to 15 parts of water.
Crude oil emulsion is made in the same way by substituting crude oil in
place of kerosene. The strength of oil emulsions is frequently
indicated by the percentage of oil in the diluted liquid:—
For a 10% emulsion add 17 gal. of water to 3 gal. stock emulsion.
For a 15% emulsion add 10 1/3 gal. of water to 3 gal. stock emulsion.
For a 20% emulsion add 7 gal. of water to 3 gal. stock emulsion.
For a 25% emulsion add 5 gal. of water to 3 gal. stock emulsion.
_Carbolic acid emulsion_.—Soap, 1 lb.; water, 1 gal.; crude carbolic
acid, 1 pt. Dissolve the soap in hot water, add the carbolic acid, and
agitate into an emulsion. For use against root-maggots, dilute with 30
parts of water.
_Soaps_.—An effective insecticide for plant-lice is _whale-oil soap_.
Dissolve in hot water and dilute so as to obtain one pound of soap to
every five or seven gallons of water. This strength is effective
against plant-lice. It should be applied in stronger solutions,
however, for scale insects. Home-made soaps and good laundry soaps,
like Ivory soap, are often as effective as whale-oil soap.
_Miscible oils_.—There are now on the market a number of preparations
of petroleum and other oils intended primarily for use against the San
José scale. They mix readily with cold water and are immediately ready
for use. While quickly prepared, easily applied, and generally
effective, they cost considerably more than lime-sulfur wash. They are,
however, less corrosive to the pumps and more agreeable to use. They
are especially valuable to the man with only a few trees or shrubs who
would not care to go to the trouble and expense to make up the
lime-sulfur wash. They should be diluted with not more than 10 or 12
parts of water. Use only on dormant trees.
_Lime and sulfur wash_.—Quicklime, 20 lb.; flowers of sulfur, 15 lb.;
water, 50 gal. The lime and sulfur must be thoroughly boiled. An iron
kettle is often convenient for the work. Proceed as follows: Place the
lime in the kettle. Add hot water gradually in sufficient quantity to
produce the most rapid slaking of the lime. When the lime begins to
slake, add the sulfur and stir together. If convenient, keep the
mixture covered with burlap to save the heat. After slaking has ceased,
add more water and boil the mixture one hour. As the sulfur goes into
solution, a rich orange-red or dark green color will appear. After
boiling sufficiently, add water to the required amount and strain into
the spray tank. The wash is most effective when applied warm, but may
be applied cold. If one has access to a steam boiler, boiling with
steam is more convenient and satisfactory. Barrels may be used for
holding the mixture, and the steam applied by running a pipe or rubber
hose into the mixture. Proceed in the same way until the lime is
slaked, when the steam may be turned on. Continue boiling for 45 min.
to an hour, or until sulfur is dissolved.
This strength can be applied safely only when the trees are dormant. It
is mainly an insecticide for San José scale, although it has
considerable value as a fungicide.
_Lime-sulfur mixtures and solutions for summer spraying_ are now coming
to take the place of bordeaux in many cases. Scott’s self-boiled
lime-sulfur mixture, described in U. S. D. A. Bureau Plant Industry
Circ. 27 is now a standard fungicide for brown-rot and black-spot or
scab of the peach. Concentrated lime-sulfur solutions, either home
boiled or commercial, are effective against apple scab and have the
advantage of not russeting the fruit. Such concentrates, testing 32°
Baume, should be diluted at about 1 gal. to 30 of water. Apply at same
time as with bordeaux. Add arsenate of lead as with bordeaux.
_Fungicide spraying formulas_.
The standard fungicide is bordeaux mixture, made in several forms. The
second most important fungicide for the home gardener is ammoniacal
copper carbonate. Sulfur dust (flowers of sulfur) and liver of sulfur
(potassium sulfide) are also useful in dry or wet sprays for surface
mildews. The lime-sulfur wash, primarily an insecticide, also has
fungicidal property.
_Bordeaux mixture_.—Copper sulfate, 5 lb.; stone lime or quicklime
(unslaked), 5 lb.; water, 50 gal. This formula is the strength usually
recommended. Stock mixtures of copper sulfate and lime are desirable.
They are prepared in the following way:—
(1) Dissolve the required amount of copper sulfate in water in the
proportion of one pound to one gallon several hours before the solution
is needed, the copper sulfate crystals being suspended in a sack near
the top of the water. A solution of copper sulfate is heavier than
water. As soon then, as the crystals begin to dissolve the solution
will sink, keeping water in contact with the crystals. In this way, the
crystals will dissolve much sooner than if placed in the bottom of the
barrel of water. In case large quantities of stock solution are needed,
two pounds of copper sulfate may be dissolved in one gallon of water.
(2) Slake the required amount of lime in a tub or trough. Add the water
slowly at first, so that the lime crumbles into a fine powder. If small
quantities of lime are used, hot water is preferred. When completely
slaked, or entirely powdered, add more water. When the lime has slaked
sufficiently, add water to bring it to a thick milk, or to a certain
number of gallons. The amount required for each tank of spray mixture
can be secured approximately from this stock mixture, which should not
be allowed to dry out.
(3) Use five gallons of stock solution of copper sulfate for every
fifty gallons of bordeaux required. Pour this into the tank. Add water
until the tank is about two-thirds full. From the stock lime mixture
take the required amount. Knowing the number of pounds of lime in the
stock mixture and the volume of that mixture, one can take out
approximately the number of pounds required. Dilute this a little by
adding water, and strain into the tank. Stir the mixture, and add water
to make the required amount. Experiment stations often recommend the
diluting of both the copper sulfate solution and the lime mixture to
one-half the required amount before pouring together. This is not
necessary, and is often impracticable for commercial work. It is
preferable to dilute the copper sulfate solution. Never pour together
the strong stock mixtures and dilute afterward. Bordeaux mixture of
other strengths, as recommended, is made in the same way, except that
the amounts of copper sulfate and lime are varied.
(4) It is not necessary to weigh the lime in making bordeaux mixture,
for a simple test can be used to determine when enough of a stock lime
mixture has been added. Dissolve an ounce of yellow prussiate of potash
in a pint of water and label it “poison.” Cut a V-shaped slit in one
side of the cork so that the liquid may be poured out in drops. Add the
lime mixture to the diluted copper sulfate solution until the
ferro-cyanide (or prussiate) test solution _will not turn brown_ when
dropped from the bottle into the mixture. It is always best to add a
considerable excess of lime.
_“Sticker” or adhesive for bordeaux mixture_.—Resin, 2 lb.; sal soda
(crystals), 1 lb.; water, 1 gal. Boil until of a clear brown color—one
to one and one-half hours. Cook in iron kettle in the open. Add this
amount to each fifty gallons of bordeaux for onions and cabbage. For
other plants difficult to wet, add this amount to every one hundred
gallons of the mixture. This mixture will prevent the bordeaux from
being washed off by the heaviest rains.
_Ammoniacal copper carbonate_.—Copper carbonate, 5 oz.; ammonia, 3 pt.;
water, 50 gal. Dilute the ammonia in seven or eight parts of water.
Make a paste of the copper carbonate with a little water. Add the paste
to the diluted ammonia, and stir until dissolved. Add enough water to
make fifty gallons. This mixture loses strength on standing, and
therefore should be made as required. It is used in place of bordeaux
when one wishes to avoid the coloring of maturing fruits or ornamental
plants. Not as effective as bordeaux.
_Potassium sulfide_.—Potassium sulfide (liver of sulfur), 3 oz.; water,
10 gal. As this mixture loses strength on standing, it should be made
just before using. It is particularly valuable for the powdery mildew
of many plants, especially gooseberry, carnation rust, rose mildew,
etc.
_Sulfur_.—Sulfur has been found to possess considerable value as a
fungicide. The flowers of sulfur may be sprinkled over the plants,
particularly when they are wet. It is most effective in hot, dry
weather. In rose houses it is mixed with half its bulk of lime, and
made into a paste with water. This is painted on the steam pipes. The
fumes destroy mildew on the roses. Mixed with lime, it has proved
effective in the control of onion smut when drilled into the rows with
the seed. Sulfur is not effective against black-rot of grapes.
_Treatment for some of the common insects_.
The most approved preventive and remedial treatments for such insect
pests as are most likely to menace home grounds and plantations are
here briefly discussed. In case of any unusual difficulty that he
cannot control, the home-maker should take it up with the agricultural
experiment station in the state, sending good specimens of the insect
for identification. He should also have the publications of the
station.
The statements that are here made are intended as advice rather than as
directions. They are chosen from good authorities (mostly from
Slingerland and Crosby in this case); but the reader must, of course,
assume his own risk in applying them. The effectiveness of any
recommended treatment depends very largely on the care, thoroughness,
and timeliness with which the work is done; and new methods and
practices are constantly appearing as the result of new investigations.
The dates given in these directions are for New York.
_Aphis or plant-louse._—The stock remedies for aphides or plant-lice
are kerosene emulsion and the tobacco preparations. Whale-oil soap is
also good. The tobacco may be applied as a spray, or in the house as
fumigation; the commercial forms of nicotine are excellent. (See page
194.) Be sure to apply the remedy before the leaves have curled and
afford protection for the lice; be sure, also, to hit the underside of
the leaves, where the lice usually are. The presence of lice on trees
is sometimes first discovered from the honey-dew that drops on walks.
Usually the emulsion is diluted with 10-15 parts of water for
plant-lice (see formula, page 194); but some of the species (as the
dark brown cherry-leaf louse) require a stronger emulsion, about 6
parts of water.
[Illustration: Fig. 234. Lady-bird beetle; larva above]
The lady-birds (one of which is shown in Fig. 234) destroy great
numbers of plant-lice, and their presence should therefore be
encouraged.
_Apple-maggot or “railroad-worm.”_—The small white maggots make
brownish winding burrows in the flesh of the fruit, particularly in
summer and early fall varieties. This insect cannot be reached by a
spray as the parent fly inserts her eggs under the skin of the apple.
When full-grown, the maggot leaves the fruit, passes into the ground,
and there transforms inside a tough, leathery case. Tillage has been
found to be of no value as a means of control. The only effective
treatment is to pick up all windfalls every two or three days, and
either to feed them out or to bury them deeply, thus killing the
maggots.
_Asparagus beetle_.—Clean cultural methods are usually sufficient to
prevent the asparagus beetle’s seriously injuring well-established
beds. Young plants require more or less protection. A good grade of
arsenate of lead, 1 lb. to 25 gal. of water, will quickly destroy the
grubs on the foliage of either young or old plants. Apply it with an
ordinary sprinkling can, or better, use one of the numerous spraying
devices now on the market. The necessity for treatment must be
determined by the abundance of the pests. They should not be permitted
to become abundant in midsummer or the over-wintering beetles may
injure the shoots in the spring.
_Blister-mite on apple and pear_.—The presence of this minute mite is
indicated by small irregular brownish blisters on the leaves. Spray in
late fall or early spring with the lime-sulfur wash, with kerosene
emulsion, diluted with 5 parts of water, or miscible oil, 1 gal. in 10
gal. of water.
_Borers_.—The only certain remedy for borers is to dig them out, or to
punch them out with a wire. Keep the space about the base of the tree
clean, and watch closely for any sign of borers. The flat-headed borer
of the apple works under the bark on the trunk and larger branches,
particularly where much exposed to sun. The dead and sunken appearance
of the bark indicates its presence. The round-headed borer works in the
wood of apples, quinces, and other trees; it should be hunted for every
spring and fall. On hard land, it is well to dig the earth away from
the base of the tree and fill the space with coal ashes; this will make
the work of examination much easier.
The peach and apricot borer is the larva of a clear-wing moth. The
larva burrows just under the bark near or beneath the surface of the
ground; its presence is indicated by a gummy mass at the base of the
tree. Dig out the borers in June and mound up the trees. At the same
time, apply gas-tar or coal-tar to the trunk from the roots to a foot
or more above the surface of the ground.
The bronze birch borer is destroying many fine white birch trees in
some parts of the country. Its presence is known by the dying of the
top of the tree. There yet is no known way of preventing this borer
from attacking white birches, and the only practicable and effective
method so far found for checking its ravages is promptly to cut and
burn the infested trees in autumn, in winter, or before May 1. There is
no probability of saving a tree when the top branches are dead,
although cutting out the dead parts may stay the trouble temporarily.
Cut and burn such trees at once and thus prevent the spread of the
insect.
_Bud-moth on apple_.—The small brown caterpillars with black heads
devour the tender leaves and flowers of the opening apple buds in early
spring. Make two applications of either 1 lb. Paris green or 4 lb.
arsenate of lead in 100 gal. of water; the first when the leaf-tips
appear and the second just before the blossoms open. If necessary,
spray again after the blossoms fall.
_Cabbage and cauliflower insects_.—The green caterpillars that eat
cabbage leaves and heads hatch from eggs laid by the common white
butterfly (Fig. 295). There are several broods every season. If plants
are not heading, spray with kerosene emulsion or with Paris green to
which the sticker has been added. If heading, apply hellebore.
The cabbage aphides, small mealy plant-lice, are especially troublesome
during cool, dry seasons when their natural enemies are less active.
Before the plants begin to head, spray with kerosene emulsion diluted
with 6 parts of water, or whale-oil soap, 1 lb. in 6 gal. of water.
The white maggots that feed on the roots hatch from eggs laid near the
plant at the surface of the ground by a small fly somewhat resembling
the common house fly. Hollow out the earth slightly around every plant
and freely apply carbolic acid emulsion diluted with 30 parts of water.
Begin the treatment early, a day or two after the plants are up or the
next day after they are set out. Repeat the application every 7 to 10
days until the latter part of May. It has also been found to be
practicable to protect the plants by the use of tightly fitting cards
cut from tarred paper. (See page 187.)
_Canker-worms._—These caterpillars are small measuring-worms or loopers
that defoliate apple trees in May and June (Fig. 217). The female moths
are wingless, and in late fall or early spring crawl up the trunks of
the trees to lay their eggs on the branches. Spray thoroughly once or
twice, before the blossoms open, with 1 lb. Paris green or 4 lb.
arsenate of lead in 100 gal. of water. Repeat the application after the
blossoms fall. Prevent the ascent of the wingless females by means of
sticky bands or wire-screen traps.
_Case-bearers on apple_.—The small caterpillars live in pistol-shaped
or cigar-shaped cases, about 1/4 in. long. They appear in spring on the
opening buds at the same time as the bud-moth and may be controlled by
the same means.
_Codlin-moth._—The codlin-moth lays the eggs that produce the pinkish
caterpillar which causes a large proportion of wormy apples and pears.
The eggs are laid by a small moth on the leaves and on the skin of the
fruit. Most of the caterpillars enter the apple at the blossom end.
When the petals fall, the calyx is open and this is the time to spray.
The calyx soon closes and keeps the poison inside ready for the young
caterpillar’s first meal. After the calyx has closed, it is too late to
spray effectively. The caterpillars become full grown in July and
August, leave the fruit, crawl down on the trunk, and there most of
them spin cocoons under the loose bark. In most parts of the country
there are two broods annually. Immediately after the blossoms fall,
spray with 1 lb. Paris green or 4 lb. arsenate of lead in 100 gal. of
water. Repeat the application 7 to 10 days later. Use burlap bands on
trunks, killing all caterpillars under them every ten days from July 1
to August 1, and once later before winter.
_Cucurbit (cucumber, melon, and squash) insects_.—Yellow, black-striped
beetles appear in numbers and attack the plants as soon as they are up.
Plant early squashes as a trap-crop around the field. Protect the vines
with screens (Fig. 229) until they begin to run, or keep them covered
with bordeaux mixture, thus making them distasteful to the beetles.
Squash vines are frequently killed by a white caterpillar that burrows
in the stem near the base of the plant. Plant a few early squashes
between the rows of the late varieties as a trap-crop. As soon as the
early crop is harvested, remove and burn the vines. When the vines are
long enough, cover them at the joints with earth in order to develop
secondary root systems for the plant in case the main stem is injured.
Dark green plant-lice feed on the under sides of squash leaves, causing
them to curl and wither. Spray with kerosene emulsion diluted with 6
parts of water. It is necessary thoroughly to cover the under side of
the leaves; the sprayer, therefore, must be fitted with an upturned
nozzle. Burn the vines as soon as the crop is harvested and keep down
all weeds.
The stink-bug is very troublesome to squashes. The rusty-black adult
emerges from hibernation in spring and lays its eggs on the under side
of the leaves. The nymphs suck the sap from the leaves and stalks,
causing serious injury. Trap the adults under boards in the spring.
Examine the leaves for the smooth shining brownish eggs and destroy
them. The young nymphs may be killed with kerosene emulsion.
_Curculio_.—The adult curculio of the plum and peach is a small
snout-beetle that inserts its eggs under the skin of the fruit and then
makes a characteristic crescent-shaped cut beneath it. The grub feeds
within the fruit and causes it to drop. When full grown, it enters the
ground, changes in late summer to the beetle, which finally goes into
hibernation in sheltered places. Spray plums just after blossoms fall
with arsenate of lead, 6 to 8 lb. in 100 gal. of water, and repeat the
application in about a week. After the fruit has set, jar the trees
daily over a sheet or curculio-catcher and destroy the beetles; this is
practically the only procedure for peaches, for they cannot be sprayed.
The quince curculio is somewhat larger than that infesting the plum and
differs in its life-history. The grubs leave the fruits in the fall and
enter the ground, where they hibernate and transform to adults the next
May, June, or July, depending on the season. When the adults appear,
jar them from the tree on sheets or curculio-catchers and destroy them.
To determine when they appear, jar a few trees daily, beginning the
latter part of May in New York.
_Currant-worm._—In the spring the small green, black-spotted larvae
feed on the foliage of currants and gooseberries, beginning their work
on the lower leaves. A second brood occurs in early summer. When worms
first appear, spray with 1 lb. Paris green or 4 lb. arsenate of lead in
100 gal. of water. Ordinarily the poison should be combined with
bordeaux (for leaf-spot).
_Cut-worms._—Probably the remedy for cut-worms most often practiced in
gardens, and which cannot fail to be effective when faithfully carried
out, is hand-picking with lanterns at night or digging them out from
around the base of the infested plants during the day. Bushels of
cut-worms have been gathered in this way, and with profit. When from
some cause success does not attend the use of the poisoned baits, to be
discussed next, hand-picking is the only other method yet recommended
that can be relied upon to check cut-worm depredations.
The best methods yet devised for killing cut-worms in any situation are
the poisoned baits, using Paris green or arsenate of lead for the
purpose. Poisoned bunches of clover or weeds have been thoroughly
tested, even by the wagon-load, over large areas, and nearly all have
reported them very effective; lamb’s quarters (pigweed), pepper-grass,
and mullein are among the weeds especially attractive to cutworms. On
small areas the making of the baits is done by hand, but they have been
prepared on a large scale by spraying the plants in the field, cutting
them with a scythe or machine, and pitching them from wagons in small
bunches wherever desired. Distributed a few feet apart, between rows of
garden plants at nightfall, they have attracted and killed enough
cut-worms often to save a large proportion of the crop; if the bunches
can be covered with a shingle, they will keep fresher much longer. The
fresher the baits, and the more thoroughly the baiting is done, the
more cut-worms one can destroy. However, it may sometimes happen that a
sufficient quantity of such green succulent plants cannot be obtained
early enough in the season in some localities. In this case, and we are
not sure but in all cases, the poisoned bran mash can be used to the
best advantage. It is easily made and applied at any time, is not
expensive, and thus far the results show that it is a very attractive
and effective bait. A tablespoonful can be quickly dropped around the
base of each cabbage or tomato plant; small amounts may be easily
scattered along the rows of onions and turnips, or a little dropped on
a hill of corn or cucumbers.
The best time to apply these poisoned baits is two or three days before
any plants have come up or been set out in the garden. If the ground
has been properly prepared, the worms will have had but little to eat
for several days and they will thus seize the first opportunity to
appease their hunger upon the baits, and wholesale destruction will
result. The baits should always be applied at this time wherever
cut-worms are expected. But it is not too late usually to save most of
a crop after the pests have made their presence known by cutting off
some of the plants. Act promptly and use the baits freely.
For mechanical means of protecting from cut-worms, see pp. 186-7.
[Illustration: Fig. 235. Elm-leaf beetle, adult, somewhat enlarged
(after Howard).]
_Elm-leaf beetle_.—Generally speaking one thorough and timely spraying
is ample to control the elm-leaf beetle (Fig. 235). Use arsenate of
lead, 1 lb. to 25 gal., and make the application to the under side of
the leaves the latter part of May or very early in June in New York.
Occasionally, when the beetle is very abundant, due in all probability
to no spraying in earlier years, it may be advisable to make a second
application, and the same may be true when conditions necessitate the
application earlier than when it will be most efficacious. This latter
condition is likely to obtain wherever a large number of trees must be
treated with inadequate outfit.
_Oyster-shell scale_.—This is an elongate scale or bark-louse, 1/8 in.
in length, resembling an oyster shell in shape and often incrusting the
bark of apple twigs. It hibernates as minute white eggs under the old
scales. The eggs hatch during the latter part of May or in June, the
date depending on the season. After they hatch, the young may be seen
as tiny whitish lice crawling about on the bark. When these young
appear, spray with kerosene emulsion, diluted with 6 parts of water, or
whale-oil or any good soap, 1 lb. in 4 or 5 gal. of water.
_Pear insects_.—The psylla is one of the most serious insects affecting
the pear tree. It is a minute, yellowish, flat-bodied, sucking insect
often found in the axils of the leaves and fruit early in the season.
They develop into minute cicada-like jumping-lice. The young psyllas
secrete a large quantity of honey-dew in which a peculiar black fungus
grows, giving the bark a characteristic sooty appearance. There may be
four broods annually and the trees are often seriously injured. After
the blossoms fall, spray with kerosene emulsion, diluted with 6 parts
of water, or whale-oil soap, 1 lb. in 4 or 5 gal. of water. Repeat the
application at intervals of 3 to 7 days until the insects are under
control.
The pear slug is a small, slimy, dark green larva which skeletonizes
the leaves in June, and a second brood appears in August. Spray
thoroughly with 1 lb. Paris green, or 4 lb. arsenate of lead, in 100
gal. of water.
_Potato insects_.—The Colorado potato beetle, or potato-bug, emerges
from hibernation in the spring and lays masses of orange eggs on the
under side of the leaves. The larvae are known as “slugs” and
“soft-shells” and cause most of the injury to the vines. Spray with
Paris green, 2 lb. in 100 gal. of water, or arsenite of soda combined
with bordeaux mixture. It may sometimes be necessary to use a greater
strength of the poison, particularly on the older “slugs.”
The small black flea-beetles riddle the leaves with holes and cause the
foliage to die. Bordeaux mixture as applied for potato blight protects
the plants by making them repellent to the beetles.
_Raspberry, blackberry, and dewberry insects_.—The greenish, spiny
larvae of the saw-fly feed on the tender leaves in spring. Spray with
Paris green or arsenate of lead, or apply hellebore.
The cane-borer is a grub that burrows down through the canes, causing
them to die. In laying her eggs, the adult beetle girdles the tip of
the cane with a ring of punctures, causing it to wither and droop. In
midsummer, cut off and destroy the drooping tips.
_Red spider_.—Minute reddish mites on the under sides of leaves in
greenhouses and sometimes out of doors in dry weather. Syringe off the
plants with clear water two or three times a week, taking care not to
drench the beds.
_Rose insects_.—The green plant-lice usually work on the buds, and the
yellow leaf-hoppers feed on the leaves. Spray, whenever necessary, with
kerosene emulsion, diluted with 6 parts of water, or whale-oil or any
good soap, 1 lb. in 5 or 6 gal. of water.
The rose-chafer is often a most pernicious pest on roses, grapes, and
other plants. The ungainly, long-legged, grayish beetles occur in sandy
regions and often swarm into vineyards and destroy the blossoms and
foliage. Spray thoroughly with arsenate of lead, 10 lb. in 100 gal. of
water. Repeat the application if necessary. (See under Rose in Chap.
VIII.)
_San José scale_.—This pernicious scale is nearly circular in outline
and about the size of a small pin head, with a raised center. When
abundant, it forms a crust on the branches and causes small red spots
on the fruit. It multiplies with marvelous rapidity, there being three
or four broods annually in New York, and each mother scale may give
birth to several hundred young. The young are born alive, and breeding
continues until late autumn when all stages are killed by the cold
weather except the tiny half-grown black scales, many of which
hibernate safely. Spray thoroughly in the fall after the leaves drop,
or early in the spring before growth begins, with lime-sulfur wash, or
miscible oil 1 gal. in 10 gal. of water. When badly infested, make two
applications, one in the fall and another in the spring. In case of
large old trees, 25 per cent crude oil emulsion should be applied just
as the buds are swelling.
In nurseries, after the trees are dug, fumigate with hydrocyanic acid
gas, using 1 oz. of potassium cyanide for every 100 cu. ft. of space.
Continue the fumigation from one-half to three-quarters of an hour. Do
not fumigate the trees when they are wet, since the presence of
moisture renders them liable to injury.
_Tent-caterpillar_.—The insect hibernates in the egg stage. The eggs
are glued in ring-like brownish masses around the smaller twigs, where
they may be easily found and destroyed. The caterpillars appear in
early spring, devour the tender leaves, and build unsightly nests on
the smaller branches. This pest is usually controlled by the treatment
recommended for the codlin-moth. Destroy the nests by burning or by
wiping out when small. Often a bad pest on apple trees.
_Violet gall-fly._—Violets grown under glass are often greatly injured
by a very small maggot, which causes the edges of the leaves to curl,
turn yellowish, and die. The adult is a very minute fly resembling a
mosquito. Pick off and destroy infested leaves as soon as discovered.
Fumigation is not advised for this insect or for red-spider.
_White-fly._—The minute white-flies are common on greenhouse plants and
often in summer on plants about gardens near greenhouses. The nymphs
are small greenish, scale-like insects found on the under side of the
leaves; the adults are minute, white, mealy-winged flies. Spray with
kerosene emulsion or whale-oil soap; or if infesting cucumbers or
tomatoes, fumigate over night with hydrocyanic acid gas, using 1 oz. of
potassium cyanide to each 1000 cu. ft. of space. (See page 188.)
_White grubs_.—The large curved white grubs that are so troublesome in
lawns and strawberry fields are the larvae of the common June beetles.
They live in the ground, feeding on the roots of grasses and weeds. Dig
out grubs from beneath infested plants. Thorough early fall cultivation
of land intended for strawberries will destroy many of the pupae. In
lawns, remove the sod, destroy the grubs, and make new sward, when the
infestation is bad.
_Treatment for some of the common plant diseases_.
The following advice (mostly adapted from Whetzel and Stewart) covers
the most frequent types of fungous disease appearing to the home
gardener. Many other kinds, however, will almost certainly attract his
attention the first season if he looks closely. The standard remedy is
bordeaux mixture; but because this material discolors the foliage the
carbonate of copper is sometimes used instead. The treatments here
recommended are for New York; but it should not be difficult to apply
the dates elsewhere. The gardener must supplement all advice of this
character with his own judgment and experience, and take his own risks.
_Apple scab_.—Usually most evident on the fruit, forming blotches and
scabs. Spray with bordeaux, 5-5-50 or 3-3-50; first, just before the
blossoms open; second, just as the blossoms fall; third, 10 to 14 days
after the blossoms fall. The second spraying seems to be the most
important. Always apply _before_ rains, not _after_.
_Asparagus rust_.—The most common and destructive disease of asparagus,
producing reddish or black pustules on the stems and branches. Late in
the fall, burn all affected plants. Fertilize liberally and cultivate
thoroughly. During the cutting season, permit no plants to mature and
cut all wild asparagus plants in vicinity once a week. Rust may be
partially controlled by spraying with bordeaux, 5-5-50, containing a
sticker of resin-sal-soda soap, but it is a difficult and expensive
operation and probably not profitable except on large acreage. Begin
spraying after cutting as soon as new shoots are 8 to 10 in. high and
repeat once or twice a week until about September 15. Dusting with
sulfur has proved effective in California.
_Cabbage and cauliflower diseases_.—Black-rot is a bacterial disease;
the plants drop their leaves and fail to head. Practice crop rotation;
soak seed 15 min. in a solution made by dissolving one corrosive
sublimate tablet in a pint of water. Tablets may be bought at drug
stores.
Club-root or club-foot is a well-known disease. The parasite lives in
the soil. Practice crop rotation. Set only healthy plants. Do not use
manure containing cabbage refuse. If necessary to use infested land,
apply good stone lime, 2 to 5 tons per acre. Apply at least as early as
the autumn before planting; two to four years is better. Lime the
seed-bed in same way.
_Carnation rust_.—This disease may be recognized by the brown, powdery
pustules on the stem and leaves. Plant only the varieties least
affected by it. Take cuttings only from healthy plants. Spray (in the
field, once a week; in the greenhouse, once in two weeks) with copper
sulfate, 1 lb. to 20 gal. of water. Keep the greenhouse air as dry and
cool as is compatible with good growth. Keep the foliage free from
moisture. Train the plants so as to secure a free circulation of air
among them.
_Chestnut_.—The bark disease of chestnut has become very serious in
southeastern New York, causing the bark to sink and die and killing the
tree. Cutting out the diseased places and treating aseptically may be
useful in light cases, but badly infected trees are incurable, in the
present state of our knowledge. Inspection of nursery stock and burning
of affected trees is the only procedure now to be recommended. The
disease is reported in New England and western New York.
_Chrysanthemum leaf-spot._—Spray with bordeaux, 5-5-50, every ten days
or often enough to protect new foliage. Ammoniacal copper carbonate may
be used, but it is not so effective.
_Cucumber diseases_.—“Wilt” is a disease caused by bacteria that are
distributed chiefly by striped cucumber beetles. Destroy the beetles or
drive them away by thorough spraying with bordeaux, 5-5-50. Gather and
destroy all wilted leaves and plants. The most that can be expected is
that the loss may be slightly reduced.
Downy mildew is a serious fungous disease of the cucumber known among
growers as “the blight.” The leaves become mottled with yellow, show
dead spots, and then dry up. Spray with bordeaux, 5-5-50. Begin
spraying when the plants begin to run, and repeat every 10 to 14 days
throughout the season.
_Currant diseases_.—Leaf-spots and anthracnose are caused by two or
three different fungi. The leaves become spotted, turn yellow, and fall
prematurely. They may be controlled by three to five sprayings with
bordeaux, 5-5-50, but it is doubtful whether the diseases are
sufficiently destructive on the average to warrant so much expense.
_Gooseberry powdery mildew_.—The fruit and leaves are covered with a
dirty white growth of fungus. In setting a new plantation, choose a
site where the land is well underdrained and where there is a good
circulation of air. Cut away drooping branches. Keep the ground
underneath free from weeds. Spray with potassium sulfide, 1 oz. to 2
gal.; begin when the buds are breaking and repeat every 7 to 10 days
until the fruit is gathered. Powdery mildew is very destructive to the
European varieties.
_Grape black-rot._—Remove all “mummies” that cling to the arms at
trimming time. Plow early, turning under all old mummies and diseased
leaves. Rake all refuse under the vine into the last furrow and cover
with the grape hoe. This cannot be too thoroughly done. The disease is
favored by wet weather and weeds or grass in the vineyard. Use surface
cultivation and keep down all weeds and grass. Keep the vines well
sprouted; if necessary sprout twice. Spray with bordeaux mixture,
5-5-50, until the middle of July, after that with ammoniacal copper
carbonate. The number of sprayings will vary with the season. Make the
first application when the third leaf shows. Infections take place with
each rain, and occur throughout the growing season. The foliage should
be protected by a coating of the spray before every rain. The new
growth especially should be well sprayed.
_Hollyhock rust_.—Fig. 212. Eradicate the wild mallow _(Malva
rotundifolia)._ Remove all hollyhock leaves as soon as they show signs
of rust. Spray several times with bordeaux mixture, taking care to
cover both sides of leaves.
_Lettuce drop or rot_.—This is a fungous disease often destructive in
greenhouses, discovered by the sudden wilting of the plants. It is
completely controlled by steam sterilization of the soil to the depth
of two inches or more. If it is not feasible to sterilize the soil, use
fresh soil for every crop of lettuce.
_Muskmelon diseases_.—“Blight” is a very troublesome disease. The
leaves show angular dead-brown spots, then dry up and die; the fruit
often fails to ripen and lacks flavor. It is caused by the same fungus
as is the downy mildew of cucumbers. While bordeaux has proved
effective in controlling the downy mildew on cucumbers, it seems to be
of little value in lessening the same disease on melons.
“Wilt” is the same as the wilt of cucumbers; same treatment is given.
_Peach diseases_.—Brown-rot is difficult to control. Plant resistant
varieties. Prune the trees so as to let in sunlight and air. Thin the
fruit well. As often as possible pick and destroy all rotten fruits. In
the fall destroy all remaining fruits. Spray with bordeaux mixture
before the buds break, or self-boiled lime-sulfur.
Leaf-curl is a disease in which the leaves become swollen and distorted
in spring and drop during June and July (Fig. 213). Elberta is an
especially susceptible variety. Easily and completely controlled by
spraying the trees once, before the buds swell, with bordeaux, 5-5-50,
or with the lime-sulfur mixtures used for San José scale.
Black-spot or scab often proves troublesome in wet seasons and
particularly in damp or sheltered situations. While this disease
attacks the twigs and leaves, it is most conspicuous and injurious on
the fruit, where it appears as dark spots or blotches. In severe
attacks the fruit cracks. In the treatment of this disease it is of
prime importance _to secure a free circulation of air_ about the fruit.
Accomplish this by avoiding low sites, by pruning, and by removal of
windbreaks. Spray as for leaf-curl and follow with two applications of
potassium sulfide, 1 oz. to 3 gal., the first being made soon after the
fruit is set and the second when the fruit is half grown.
Yellows is a so-called “physiological disease.” Cause unknown.
Contagious, and serious in some localities. Known by the premature
ripening of the fruit, by red streaks and spots in the flesh, and by
the peculiar clusters of sickly, yellowish shoots that appear on the
limbs here and there (Fig. 215). Dig out and burn diseased trees as
soon as discovered.
_Pear diseases_.—Fire-blight kills the twigs and branches, on which the
leaves suddenly blacken and die but do not fall. It also produces
cankers on the trunk and large limbs. Prune out blighted branches as
soon as discovered, cutting 6 to 8 in. below the lowest evidences of
the disease. Clean out limb and body cankers. Disinfect all large
wounds with corrosive sublimate solution, 1 to 1000, and cover with
coat of paint. Avoid forcing a rapid, succulent growth. Plant the
varieties least affected.
Pear scab is very similar to apple scab. It is very destructive to some
varieties, as, for example, Flemish Beauty and Seckel. Spray three
times with bordeaux, as for apple scab.
_Plum and cherry diseases_.—Black-knot is a fungus, the spores of which
are carried from tree to tree by the wind and thus spread the
infection. Cut out and burn all knots as soon as discovered. See that
the knots are removed from all plum and cherry trees in the
neighborhood.
Leaf-spot is a disease in which the leaves become covered with reddish
or brown spots and fall prematurely (Fig. 211); badly affected trees
winterkill. Often, the dead spots drop out, leaving clear-cut holes.
Spray with bordeaux, 5-5-50. For cherries, make four applications:
first, just before blossoms open; second, when fruit is free from
calyx; third, two weeks later; fourth, two weeks after third. In plums
it may be controlled by two or three applications of bordeaux, 5-5-50.
Make the first one about ten days after the blossoms fall and the
others at intervals of about three weeks. This applies to European
varieties. Japan plums should not be sprayed with bordeaux.
_Potato diseases_.—There are different kinds of potato blight and rot.
The most important are early blight and late blight—both fungous
diseases. Early blight affects only the foliage. Late blight kills the
foliage and often rots the tubers. Two serious troubles often mistaken
for blight are: (1) Tip burn, the browning of the tips and margins of
the leaves due to dry weather; and (2) flea-beetle injury, in which the
leaves show numerous small holes and then dry up. The loss from blight
and flea-beetles is enormous—often, one-fourth to one-half the crop.
For blight-rot and flea-beetles spray with bordeaux, 5-5-50. Begin when
the plants are 6 to 8 in. high and repeat every 10 to 14 days during
the season, making 5 to 7 applications in all. Use 40 to 100 gal. per
acre at each application. Under conditions exceptionally favorable to
blight it will pay to spray as often as once a week.
Scab is caused by a fungus that attacks the surface of the tubers. It
is carried over on diseased tubers and in the soil. In general, when
land becomes badly infested with scab, it is best to plant it with
other crops for several years. (See page 190.)
_Raspberry diseases_.—Anthracnose is very destructive to black
raspberries, but not often injurious to the red varieties. It is
detected by the circular or elliptical gray scab-like spots on the
canes. Avoid taking young plants from diseased plantations. Remove all
old canes and badly diseased new ones as soon as the fruit is gathered.
Although spraying with bordeaux, 5-5-50, will control the malady, the
treatment may not be profitable. If spraying seems advisable, make the
first application when the new canes are 6 to 8 in. high and follow
with two more at intervals of 10 to 14 days.
Cane-blight or wilt is a destructive disease affecting both red and
black varieties. Fruiting canes suddenly wilt and die. It is caused by
a fungus which attacks the cane at some point and kills the bark and
wood, thereby causing the parts above to die. No successful treatment
is known. In making new settings, use only plants from healthy
plantations. Remove the fruiting canes as soon as the fruit is
gathered.
Red-rust is often serious on black varieties, but does not affect red
ones. It is the same as red rust of blackberry. Dig up and destroy
affected plants.
_Rose diseases_.—Black leaf-spot is one of the commonest diseases of
the rose. It causes the leaves to fall prematurely. Spray with
bordeaux, 5-5-50, beginning as soon as the first spots appear on the
leaves. Two or three applications at intervals of ten days will very
largely control the disease. Ammoniacal copper carbonate may be used on
roses grown under glass. Apply once a week until disease is under
control.
For mildew on greenhouse roses, keep the steam pipes painted with a
paste made of equal parts lime and sulfur mixed up with water. The
mildew is a surface-feeding fungus and is killed by the fumes of the
sulfur. Outdoor roses that become infested with the mildew may be
dusted with sulfur, or sprayed with a solution of potassium sulfide, 1
oz. to 3 gal. water. Spray or dust with the sulfur two or three times
at intervals of a week or ten days.
_Strawberry leaf-spot._—The most common and serious fungous disease of
the strawberry; also called rust and leaf-blight. The leaves show spots
which at first are of a deep purple color, but later enlarge and the
center becomes gray or nearly white. The fungus passes the winter in
the old diseased leaves that fall to the ground. In setting new
plantations, remove all diseased leaves from the plants before they are
taken to the field. Soon after growth begins, spray the newly set
plants with bordeaux, 5-5-50. Make three or four additional sprayings
during the season. The following spring, spray just before blossoming
and again 10 to 14 days later. If the bed is to be fruited a second
time, mow the plants and burn over the beds as soon as the fruit is
gathered. Plant resistant varieties.
_Tomato leaf-spot._—The distinguishing character of this disease is
that it begins on the lower leaves and works towards the top, killing
the foliage as it goes. It is controlled with difficulty because it is
carried over winter in the diseased leaves and tops that fall to the
ground. When setting out plants, pinch off all the lower leaves that
touch the ground; also any leaves that show suspicious-looking
dead-spots. The trouble often starts in the seed-bed. Spray plants very
thoroughly with bordeaux, 5-5-50, beginning as soon as the plants are
set out. Stake and tie up for greater convenience in spraying. Spray
under side of the leaves. Spray every week or ten days.