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## CHAPTER VI

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.

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).

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.

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.

Screens and covers.

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.

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):--

"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."

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.

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.

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.

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.

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