Chapter 3. PROTECTING PLANTS FROM THINGS THAT PREY ON THEM

Table of Contents

_Screens and covers._
_Fumigating._
_Soaking tubers and seeds._
_Spraying._
_Insecticide spraying formulas._
_Paris green._--The standard insecticidal poison. This is used in
_Arsenate of lead._--This can be applied in a stronger mixture than
_White Hellebore._--For wet application, use fresh white hellebore, 4
_Tobacco._--This is a valuable insecticide and is used in several forms.
_Kerosene emulsion._--Hard, soft, or whale-oil soap, 1/2 lb.; water, 1
_Carbolic acid emulsion._--Soap, 1 lb.; water, 1 gal.; crude carbolic
_Soaps._--An effective insecticide for plant-lice is _whale-oil soap._
_Miscible oils._--There are now on the market a number of preparations
_Lime and sulfur wash._--Quicklime, 20 lb.; flowers of sulfur, 15 lb.;
_Lime-sulfur mixtures and solutions for summer spraying_ are now coming
_Fungicide spraying formulas._
_Bordeaux mixture._--Copper sulfate, 5 lb.; stone lime or quicklime
_"Sticker" or adhesive for bordeaux mixture._--Resin, 2 lb.; sal soda
_Ammoniacal copper carbonate._--Copper carbonate, 5 oz.; ammonia, 3 pt.;
_Potassium sulfide._--Potassium sulfide (liver of sulfur), 3 oz.; water,
_Sulfur._--Sulfur has been found to possess considerable value as a
_Treatment for some of the common insects._
_Aphis or plant-louse._--The stock remedies for aphides or plant-lice
_Apple-maggot or "railroad-worm."_--The small white maggots make
_Asparagus beetle._--Clean cultural methods are usually sufficient to
_Blister-mite on apple and pear._--The presence of this minute mite is
_Borers._--The only certain remedy for borers is to dig them out, or to
_Bud-moth on apple._--The small brown caterpillars with black heads
_Cabbage and cauliflower insects._--The green caterpillars that eat
_Canker-worms._--These caterpillars are small measuring-worms or loopers
_Case-bearers on apple._--The small caterpillars live in pistol-shaped
_Codlin-moth._--The codlin-moth lays the eggs that produce the pinkish
_Cucurbit (cucumber, melon, and squash) insects._--Yellow,
_Curculio._--The adult curculio of the plum and peach is a small
_Currant-worm._--In the spring the small green, black-spotted larvae
_Cut-worms._--Probably the remedy for cut-worms most often practiced in
_Elm-leaf beetle._--Generally speaking one thorough and timely spraying
_Oyster-shell scale._--This is an elongate scale or bark-louse, 1/8 in.
_Pear insects._--The psylla is one of the most serious insects
_Potato insects._--The Colorado potato beetle, or potato-bug, emerges
_Raspberry, blackberry, and dewberry insects._--The greenish, spiny
_Red spider._--Minute reddish mites on the under sides of leaves in
_Rose insects._--The green plant-lice usually work on the buds, and the
_San Jos scale._--This pernicious scale is nearly circular in outline
_Tent-caterpillar._--The insect hibernates in the egg stage. The eggs
_Violet gall-fly._--Violets grown under glass are often greatly injured
_White-fly._--The minute white-flies are common on greenhouse plants and
_White grubs._--The large curved white grubs that are so troublesome in
_Treatment for some of the common plant diseases._
_Apple scab._--Usually most evident on the fruit, forming blotches and
_Asparagus rust._--The most common and destructive disease of asparagus,
_Cabbage and cauliflower diseases._--Black-rot is a bacterial disease;
_Carnation rust._--This disease may be recognized by the brown, powdery
_Chestnut._--The bark disease of chestnut has become very serious in
_Chrysanthemum leaf-spot._--Spray with bordeaux, 5-5-50, every ten days
_Cucumber diseases._--"Wilt" is a disease caused by bacteria that are
_Currant diseases._--Leaf-spots and anthracnose are caused by two or
_Gooseberry powdery mildew._--The fruit and leaves are covered with a
_Grape black-rot._--Remove all "mummies" that cling to the arms at
_Hollyhock rust._--Fig. 212. Eradicate the wild mallow _(Malva
_Lettuce drop or rot._--This is a fungous disease often destructive in
_Muskmelon diseases._--"Blight'" is a very troublesome disease. The
_Peach diseases._--Brown-rot is difficult to control. Plant resistant
_Pear diseases._--Fire-blight kills the twigs and branches, on which the
_Plum and cherry diseases._--Black-knot is a fungus, the spores of which
_Potato diseases._--There are different kinds of potato blight and rot.
_Raspberry diseases._--Anthracnose is very destructive to black
_Rose diseases._--Black leaf-spot is one of the commonest diseases of
_Strawberry leaf-spot._--The most common and serious fungous disease of
_Tomato leaf-spot._--The distinguishing character of this disease is

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.

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.

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.]

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.

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.

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. 227. A barrel outfit, showing nozzles on extension rods for trees.]