Chapter 21

Diseases And Their Control #2

Sooty Mould

Sooty mould, due to Dimerosforium, Aposporium, or Capnodium, cannot exist without aphides and their honey-dew. It is a disease of late summer and autumn. This fungus not only disfigures the plants with its black coating of the leaves and branches, but it blocks the stomata. No direct treatment is of any use; aphides must be controlled.

Ants

Ants are commonly believed to destroy aphides, but, on the contrary, they protect them in every possible way, and even transfer them from plant to plant. Ants are attracted by honey-dew, and can be eliminated only by controlling aphides,

Thrips

Thrips are not imported, as was once thought. There are nearly forty different types of indigenous thrips affecting various flowers. In the rose thrips (Thrips imaginis) the young are orange, while the adults are brown and have two pairs of fringed wings (see Fig. 16). They are about one-twelfth of an inch long and very slender. Most of the insects hibernate as pupae in the soil, or as dormant adults in sheltered positions. As spring progresses and the days become warmer the pupae and dormant adults reawaken, greatly increasing the numbers of active thrips. A few active insects can be found on a sunny day even in midwinter. The numbers of early spring thrips depend upon the autumn numbers and the weather. They feed on grains, grasses, and legumes, moving to roses as the second generation appears; this coincides with the blooming flush in October and November. Lush growth of winter grasses followed by dry weather and hot winds from the inland favour heavy infestation. Rain greatly decreases the numbers and is always very welcome in late or mid October, even if thrips are not unusually prevalent

Active thrips are present throughout the year, but they are most numerous and most damaging to roses in the spring. After reaching the young unopened bud they insinuate themselves between the petals. In a well-developed bloom they are to be found in greatest numbers in the innermost parts, yet they do most damage to the edges of the petals, where, by sucking, they cause a browning, and, usually, some degree of gumming together of the petals. This results sometimes in the balling of the bloom. Unless preventive spraying is done, almost an entire spring crop of roses can be lost when thrips are in plague numbers. The damage is most serious in light-coloured flowers; markings on dark roses are less obvious. Thrips cause silvery markings on foliage, too.

NATUBAl ttZl Fig. 16. Adult female of Thrips imaginis. (By courtesy of the New South Wales Department of Agriculture.)

There are several generations of thrips each season, but they usually become less noticeable and less damaging to roses after the first blooming. The second crop of flowers, which extends onwards from December, always has a lot of thrips, but the roses have fewer petals and open quickly, leaving little opportunity for damage.

All rubbish heaps must be avoided, and the soil should be kept well stirred. Systox, E605, Lindane, and DDT will all control thrips, and have removed all anxieties about our spring crop of roses. The first spraying should be done just before the sepals begin to reveal the tightly folded petals, and should be repeated at intervals of five to ten days for at least two weeks in spring. These same applications will, of course, control aphides and caterpillars as well, and, for that purpose, will have been used a few weeks earlier, and repeated. It is important not to use household sprays, for most of these will injure plants.

Leaf-Cutter Bees

The leaf-cutter bee (Megachile centuncularis), is a large insect something like a honey-bee. It cuts regular semi-circular portions from the margins of rose leaves, carries them away, makes a tubular nest in crevices of wood, brick walls, or soil, lays an egg in it, and then exactly fits a cap to the tube. When possible, the nests should be traced and destroyed at dusk, when the bees are at home. Spraying foliage with arsenate of lead is helpful. The leaf-cutter bee is not a serious menace.

Caterpillars (Plate 47)

Caterpillars are considered best as a group; all are voracious feeders. The most common are:

1.	The various looper caterpillars of the Geometrida family. Many live on other plants as well as on roses. They are nearly all stick-like in both form and colour, making them difficult to detect. Most feed by night, but during the day take a firm hold on a twig with their two pairs of prolegs, and project at an acute angle. When travelling they raise their mid-part into a loop.
2.	The painted apple moth {Teira amtrtoides) Plate 47 has a caterpillar a little over an inch long. It has one loose tuft of long hair at the tail and two near the head; the whole body is covered with tufts of shorter hair. On emerging from the egg the caterpillar is almost black, but changes to greyish-brown as it matures. The expanded wings are brown and yellow with grey markings; the hind-wings have a large basal patch of orange. Except for two useless vestigial appendages the female is wingless. Soon after reaching maturity she lays five hundred to a thousand eggs on the empty cocoon from which she has recently emerged. This is sometimes called the tussock moth.
3.	The light-brown apple moth (Tortix [Cacaecia] post vittana) Plate 47 has a greenish caterpillar that curls up in the leaves and buds of roses. About an inch in length, it is very active, and so elusive that when leaves are seen rolled or gummed together it is advisable to squeeze them between finger and thumb before looking for the culprit. The moth has a wing-span of three-quarters of an inch. It is yellowish-brown with lightly barred wings, and very evasive. The eggs are laid on the young flower-buds, which the caterpillars penetrate immediately they are hatched. They move from one bud to another, destroying each in turn, until they reach maturity in about two weeks. Then they join a couple of leaves together, or curl one leaf over on itself, spin a web, and turn into a chrysalis.
4.	The stick-case moths (Entometit, ThyruUypteryx, etc.) cause relatively little harm.
5.	Cutworms {Agrotis heliothus, etc.) rise from debris and the soil by night, and one caterpillar can do widespread damage, most commonly in September and January. Eggs are deposited at night. They hatch in eight to ten days and produce mature moths in seven to eight weeks. Each moth lays two hundred to five hundred eggs.

All these caterpillars can be controlled by spraying with arsenate of lead, but it must be applied at or very soon after hatching time, which in most cases will be early spring. A preparation of Lindane (the gamma isomer of BHC), or DDT in white-oil emulsion is at least equally as effective, and is not poisonous to birds. Baits of bran with arsenate of calcium give better results in killing cutworms. Be careful to lay the baits in the evening and to gather them early next morning before birds can get them and be poisoned.

Less Common Diseases

The gumleaf grasshopper (Australian katydid, or Caedicia olivacea) Plate 47 is a nocturnal feeder capable of great destruction of flower-buds. Fortunately it is not a common pest, and tends to confine itself to the one plant, or even to the one bud, for several nights. It is easy to catch by torchlight because of this habit, its slow movement, and a squeak that it emits. Spraying with DDT in white-oil emulsion or with arsenate of lead will eradicate it.

The red spider is a well-known garden pest. It is not an insect, but an arachnid, Tetranychus telarius, and is a greater menace to smaller plants than to roses. However, the extent of the damage done by red spider has increased enormously since we have been using the gamma isomer of BHC and DDT, because these sprays kill, as well as pests, the natural enemies of many pests, including those that destroy red spiders, but they have no effect on the red spiders themselves. Consequently this pest is allowed to multiply rapidly and unchecked. Until the introduction of organic phosphates we had no spray that would kill red spiders. These sprays would eradicate this pest when applied twice at an interval of about ten days, even though it is difficult to get sprays onto the spiders, because of their habit of sheltering. But organic phosphates are not available any longer to most people. In their stead we may use a new group of preparations containing Chlorparacide; these are discussed in detail later in this chapter. Red spiders are rare in gardens that are watered once or more each day. They prefer dry, sheltered positions, and feed in large numbers on the under-surface of leaves, which they cover with a fine web. Red spider and mildew are the chief diseases affecting roses grown in glasshouses. Karathane will control both.

The Rutherglen bug or fly (Nysius vinitor) rarely comes in damaging numbers. Indigenous to Australia, this insect is greyish brown and a quarter of an inch long. It is very active and drops to the ground immediately a plant is touched. A beak, or rostrum, enables the fly to suck sap, causing plants to wither and die. The eggs are laid under the soil, or among rubbish and weeds. It is best controlled by E605, Systox, Lin-dane, or DDT.

Harlequin bugs (Dindymus versicolor) are well-known red orange, yellow, and black garden pests; they are sometimes called soldier bugs. They feed by sucking, and take shelter under garden rubbish, in undergrowth, and between fence-rails and pailings. Kill as many as can be gathered by hand, and use a blowlamp, or boiling water from a kettle, along the back of fence-rails.

Sunburn causes serious losses in some areas during hot, dry summer months. Sometimes it kills, but, more commonly, in lesser degree, it appears as dead branches, or brown dead patches on the sunny side of branches. It is due to the sap concentration becoming too high, secondary to insufficient soil moisture or unduly fast loss of water from the plant by evaporation. Trunks of standards, especially those on R. multiflora stock, must be shaded by stakes, and badly affected branches should be cut away. Sunburn must not be confused with rose-leaf scorch, which is a distinct disease, and has never been reported in Australia.

Rose-root rot can be due to any of several fungi, the commonest of which is Armillaria mellea (honey agaric). It spreads through the soil and invades roots, growing up under the bark. It seldom extends much above ground level, but grows freely at the base of the plant. Death ensues in almost all plants attacked; sometimes the process is rapid, sometimes slow. The fungus is native to many countries, including Australia. It is common in forest soils, especially when wet or poorly drained. Dead wood, and decaying roots and bark, are ideal breeding grounds. If it is desired to replant an infected area it should be dug over several times, all dead wood removed from it, and a light dressing of lime applied. The soil should be aerated well by further digging, and, each time, it should be left in as rough a state as possible.

Stem canker is due to the fungus Conionthyrium fuckelii, which infects plants through wounds. Purplish discoloration first appears round the wound, then the bark cracks and, later, tissue-growths protrude, bearing the fruiting bodies of the fungus. The disease can be controlled by cutting away the affected parts.

Crown gall is caused by the presence in the soil of Bacterium tumefaciens, introduced by infected plants. The characteristic symptoms are the production of gall-like knobs round the crown or base of the plant; occasionally it occurs higher on the stem. The galls vary greatly in size, and cause stunting of the plant. This disease is prevalent in roses grown in glasshouses overseas, and is common out of doors in Australia, especially in alkaline soils. Affected plants must be dug up and burnt. At least two barrow-loads of soil should be removed, and there should be no replanting in that position for at least two years.

Sprays And Dusts

In the control of diseases Nature plays a very big part by means of birds, insects, sunshine, and water; but, especially under circumstances of intensive cultivation, we find it necessary to supplement these measures by applying chemicals. Many preparations have been mentioned they are but a small percentage of those offered for sale. These compounds act in varying ways, and accordingly may be classified as fungicides, ovicides, contact poisons, and stomach poisons. They are used as dusts in powder form, or as liquid sprays in solutions or emulsions. In general, sprays are more effective than dusts.

There are many manufacturers marketing sprays and dusts; each firm sells its products under proprietary names. Often similar products are sold under quite dissimilar names, and occasionally the one firm will sell one product under different names in each of several countries. These practices are very misleading, especially when, in addition, each preparation is alleged to be a panacea for a multitude of garden diseases. Many of these claims have some justification, but usually each spray or dust has one main use. It may give some slight assistance in controlling other diseases, but is almost always inferior to other types available for those purposes.

Every garden has its pests and diseases, and garden equipment is not complete without some type of spraying apparatus and at least some of the more commonly needed chemical preparations. A stirrup pump or a knapsack spray is necessary in all but the very small gardens. Most sprays tend to run off foliage unless a "spreader" is added. Several are described later.

In the following pages an attempt is made to explain, and to reduce to as small a number as possible, the recommended sprays and dusts, while maintaining efficient control of diseases.

Our most important fungicides are preparations of TMTD, copper, sulphur, and white-oil emulsions. Copper and sulphur act on the young mycelium of the fungus as it emerges from the spore. White-oil emulsions act on the more mature fungus, as well as on the young stage. The preparations of TMTD (tetramethyl thiuram disulphide) have been in use in Australia for only a few years; the best known of them are Thiotox, and TMTD Fungicide. They combine the effects of copper and sulphur on fungi, and represent one of the greatest modern advances in the control of plant diseases.

Thiotox contains eighty per cent of TMTD, and at the concentrations recommended by the manufacturers it is harmless to foliage. On the contrary, the foliage of plants that have been sprayed several times with Thiotox assumes a noticeably healthy dark-green colour. The powder, being insoluble, is applied as a suspension, but leaves very little disfiguring deposit on the plants. If it is used every ten to fourteen days black spot, mildew, and rose rust will be kept out of any rose garden, and the consequent difference in the vigour of the plants and the general appearance of the garden is quite amazing. It clearly demonstrates the value of the maintenance of health in the foliage, and this had not been possible with earlier sprays. It is compatible with Chlorparacide and the gamma isomer of BHC (Lindane), but not with DDT. By adding Lindane to Thiotox one can control all the fungus diseases, aphis, thrips, and caterpillars with the one mixture. It is incompatible with copper compounds, but this combination is unnecessary.

Bordeaux mixture, Bordinette, and Cuprox are the best of the copper fungicides. Their main use is in black-spot control, and, as already stated, they are superseded by Thiotox. Because the fungus of black spot is inside the leaves it is inaccessible, and so all of these sprays, including Thiotox, are used to prevent black spot infection, or the spreading of it if already present, because cure of the infection is impossible. It is better to apply sprays before rain than after it, for rain scatters the spores. The copper sprays are apt to cause scorching of foliage if used on very hot days.

Bordeaux mixture is compounded from lime and copper sulphate (bluestone) and its fungicidal value was discovered by chance over a hundred years ago near Bordeaux. Ready-mixed powder is cheap, and easy to dissolve and apply. The strength of the solution advised by the maker will vary with the season in which it is to be used, and will be found printed on the container. It does not keep well, and so some gardeners prefer to mix their own solution. Only glass, wooden, earthenware, or copper vessels should be used in preparing the mixture; never use iron or zinc ones. The necessary quantities will be one pound each of freshly burnt lime and copper sulphate. For winter spraying, ten gallons of water should be added; for summer spraying, twelve and a half gallons will be needed.

Copper sulphate is not as readily soluble as many people believe; wrap it in coarse hessian and suspend it just beneath the surface of two and a half gallons of water; leave it for twenty-four hours. Take the lime in another vessel and slake it by adding water, little by little; it will become very hot, and therefore great care must be taken if it is in a glass or earthenware vessel. When the lime is slaked, make up the volume to seven and a half gallons in winter or ten gallons in summer by adding water. Pour the two and a half gallons of copper sulphate solution into the milk of lime and stir thoroughly. Finely strain the mixture before pouring it into the sprayer, since any coarse particles may choke the spray nozzle, causing much loss of time and annoyance. Bordeaux mixture deteriorates quickly in liquid form, and so it should be used as soon as possible after mixing. It is incompatible with almost all other sprays, and is strongly alkaline.

Bordinette is much better than Bordeaux mixture in two ways, namely, it keeps well and it dissolves readily in cold water. It should be used in the strength of one pound to ten gallons of water, or twelve and a half gallons of water, according to the season.

Cuprox is another proprietary preparation, and a further improvement. Its active constituent is re-dispersible copper oxychloride. It is neither acid nor alkaline, and is compatible with wettable and colloidal sulphurs, E605, Lindane, DDT, and Chlorparacide.
Sulphur is available for use in many forms as sprays and dusts. The best of these are the wettable sulphur and colloidal sulphur proprietary preparations; they replace and excel lime-sulphur and flowers of sulphur. They are all used in mildew control, affecting the spores of the fungus.

Wettable and colloidal sulphurs, such as Wetsul and Sper-sul, are cheap, easily mixed with cold water, and are safe to use, except on very hot days, when all sulphur preparations are apt to cause scorching of the foliage. They are compatible with E605, Lindane, DDT, Chlorparacide, and preparations of copper oxychloride.

Lime sulphur is obtainable as a ready-mixed powder, but needs to be carefully strained before using, so as to avoid blocking of the spray nozzle. It has an unpleasant odour, and should never be sprayed on paint-work, for it will blacken it. Lime sulphur was discovered by accident in the early part of the nineteenth century. It is strongly alkaline, and is incompatible with all sprays except nicotine sulphate.

Flowers of sulphur were once a traditional preventive and curative for mildew. The powder is sprinkled over the plants, but its action depends on sulphur dioxide being made from it on the ground, and the fumes rising through the foliage. A calm day is necessary for several reasons the powder and fumes are easily blown away, and the fine particles of sulphur are very irritating to one's eyes. Massey dust consists of nine parts of flowers of sulphur and one part of arsenate of lead powder. It combines the action of the two chemicals and is advocated overseas for control of black spot as well as mildew.

Shirlan for mildew control has one advantage over sulphur preparations in that it is safe to use on hot days, but otherwise it is not as good. Its active principle is a salicylanide with sulphonated organic matter.

Karathane has not been used extensively in Australia, yet. Oversea reports are enthusiastic over it as both a fungicide for killing established mildew and a miticide. Arathane, Mildex, and Iscothan are alternative trade names. Its full chemical name is dinitrocapryl phenyl crotonate.

From the point of view of control, insects may be divided into two groups leaf-eaters and sap-suckers. Many leaf-eating insects do no harm in the insect stage of their life cycle that is, while they are moths or butterflies. During that phase they mate and deposit eggs, but neither eat nor drink. The damage is done by their caterpillars, which are best killed by stomach poison, the chief of which are E605, Systox, arsenates of lead and calcium, metaldehyde, and rotenone.

Arsenic is the most potent stomach poison for garden uses. Bought as arsenate of lead paste, it is used for killing caterpillars, being sprayed on plants in the strength of one ounce of paste to each gallon of water. Cutworms are large and need to eat a lot of a plant before getting a fatal dose of arsenic. For them, it is better to lay baits made up of one pound of bran, one ounce of calcium arsenate, a pinch of salt, and enough water to make it damp; it must be thoroughly mixed. Small baits should be placed near each rose plant, preferably after sunset to avoid poisoning birds, and to save the baits from drying before the cutworms reach them. Dry baits should be removed promptly, for they are useless, besides killing birds. Arsenates are compatible only with nicotine sulphate. Mixed with soaps, they interact to form soluble compounds of sodium and arsenic. These are very powerful poisons to plants of all kinds, and are the bases of many weed-killers.

Metaldehyde is less poisonous than arsenic and does not attract birds readily. It is effective in controlling slugs and snails, which can cause damage to rose blooms.

Rotenone is the active constituent of all Derris dust preparations. These are non-poisonous to mammals and so are safe on edible plants for human or animal consumption, but they are not nearly as lethal to pests as arsenic, and we do not need to consider the aspect of animal foods in our flower gardens.

Stomach poisons on the surface of the foliage are, obviously, useless against sap-sucking insects. They can be attacked by contact sprays, or by rendering the sap poisonous to them. Contact sprays act in widely differing ways. Those that are absorbed by plants, either through the leaves or the roots, and act as stomach poisons to sap-suckers, are known as systemic poisons; a great deal of research is being done in endeavour to develop more of them.

The greatest advance ever made in the control of garden pests came with the introduction of a new group of products known as organic phosphates. HETP was the first of these to be available; parathion and E605 came soon after it. Any difference in the chemical composition of parathion and E605 is of a minor nature and of only academic interest, having no practical importance. The two names may be regarded as freely interchangeable, if not synonymous, but, to avoid confusion, only one name, E6o5, has been used in the section of this chapter that deals with insects. HETP seems a little quicker in its killing action than E605. They were by far the best contact sprays we had ever had for aphis, thrips, red spider, and pea mite, and were the only preparations that will kill the last two of these pests as adults; two sprayings at an interval of ten days are advisable. More recently Chlorparacide
has been introduced, and it deals effectively with the eggs and pupae of arachnids, without having the disadvantage of being poisonous to man it is not a phosphoric preparation.

The latest developments of organic phosphate preparations take the form of systemic insecticides, so called because they are absorbed into the system of the plant and render the sap toxic to pests. They also kill all insects rapidly by contact at the time of application and have persistent action on the surface of the plant, similar to that of E605. After absorption they have no harmful effect on the natural enemies of plant pests, of course, because such predators do not suck sap. E605 is absorbed by the plant and acts in this same manner but in much lesser degree. Systematic sprays are absorbed through both leaves and roots and they reach all parts of a plant irrespective of whether the spray has or has not covered the foliage completely. Once absorbed, rain or watering cannot wash them away, thus allowing them to remain fully effective for three or four weeks. Systemic sprays, therefore, need to be used less often than E605, which more than off-sets their higher cost. It is possible to obtain good results merely by watering the soil with systemic sprays. This avoids the dangers encountered in spraying, but is rather wasteful.

These organic phosphate sprays seemed, at first, to be what all horticulturists had been hoping for for many years. We knew that they were extremely poisonous to human beings, but we did not anticipate the fatalities of which reports were received quite soon. Fortunately, it seems that none of these tragedies occurred in Australia before the introduction in some States of regulations governing the use of these sprays. It must be conceded that there is no great danger if organic phosphates are handled with care, and it is regrettable that it is necessary to protect people against their own lack of caution. The new regulations make it compulsory for any person using organic phosphate sprays to wear waterproof overalls, a waterproof hood, gloves and boots of rubber or other suitable protective material, and a full face-piece respirator with charcoal container and filter pad. All clothes and protective coverings must be washed thoroughly upon ceasing work each day, as well as any exposed parts such as the face, hands, and forearms. As yet, we have no spray or combination of sprays to equal the usefulness of organic phosphates. The nearest approach to them can be made by mixing Chlorparacide with Lindane and DDT as in Spraymate. This combination is inferior to E605 solely because it is slower in action and has no effect as a systemic poison. This is important only in spring when aphides reproduce so quickly.

As a further precaution, it is illegal to sell any organic phosphate spray in any quantity less than one pint; this amount is quite costly. The sum total of all these regulations is that the use of organic phosphates is practicable only for those who spray on a large scale. For them, the elaborate precautions and expense are more than compensated for by the results; actually, where large amounts of sprays are needed, organic phosphates are less costly than most other materials, particularly if one considers the saving in labour costs, as a result of spraying being required less frequently. This makes it worth while to give more detailed consideration to HETP, E6o5, and systemic sprays.

HETP does not keep well after it has been diluted, and it has no persistent action, whereas E605 may be stored indefinitely in diluted form, and remains effective on the plant for at least two weeks. Systemic sprays are absorbed by the leaves, rendering the sap poisonous to sucking insects, such as aphides and harlequin bugs; they are also ovicidal. In this last respect they are not as potent as tar distillate, but have the great compensation of being harmless to young foliage. They are compatible with copper oxychloride, and colloidal and wettable sulphur preparations. All alkaline preparations, such as lime sulphur, Bordeaux mixture, and alkalinized white oils accelerate greatly the breaking down of E605, and systematic sprays, - and so destroy their persistent action.

HETP is available in Australia and New Zealand under several trade names, including Hexone, Vallo HETP, Tephos, Tetraphos, and Demite, as well as under the name of HETP, which is an abbreviation for hexaethyl tetraphosphate. E605 or parathion, chemically known as para nitrophenyl diethyl thiosulphate, is available as Phosfone 20, E605 Folidol, Para-phos, and Parathion. Systox and Sytam are two examples of systemic sprays. Neither marks foliage.

Top: A bunch of PICTURE. Bottom: A bowl of mixed roses. Plate 48 RAPTURE. A bunch staged for exhibition. This Hybrid Tea is the darkest of the Ophelia group of roses, by no means new but still great favourites. Plate 49

DDT (dichloro-diphenyl-trichloroethane) is one of the most powerful of all insecticides. It is a contact poison, acting on the insect's nervous system, and is absorbed through the footpads. DDT is useful against thrips, aphides, and Rutherglen bugs when applied in a white-oil or wax base. If any is allowed on open flowers it will kill the bees that visit those flowers. It is only slightly toxic when swallowed, and is almost useless if not mixed with a white-oil or mayonnaise emulsion (as in Pes-pruf-20), or with some other base (as in Rucide). Rucide needs to be warmed, but not boiled, and adheres to the foliage better than the white-oil emulsion preparations. DDT preparations are cheap and easy to apply. They have persistent action lasting two to three weeks, but, of course, a good unbroken film cannot be maintained without more frequent spraying on young flower-buds that are swelling rapidly and are ready for invasion by thrips. The film is torn apart by the enlarging surface. In the spring aphides sometimes seem to breed faster than DDT can kill the older generations. E605 and Lindane act more quickly, while with systemic sprays the maintenance of an unbroken cover is unnecessary.

Spraying with white-oil suspensions of DDT causes white spots to remain on the foliage of plants. These can be wiped off easily with an oily rag if the flowers are cut for indoor use, but should be left on the leaves that remain on the plant. DDT loses its potency when mixed with TMTD sprays, whereas Lindane remains effective, as also do organic phosphates.

Benzene hexachloride (BHC) is a compound which was discovered first by Michael Faraday in 1825. It can exist in four forms, known as the alpha, beta, gamma, and delta isomers of BHC; each has the same molecular formula, but different properties. In 1943 it was found that the gamma isomer had insecticidal properties which in many respects are the most potent ever discovered; yet it is almost entirely harmless to men and animals. DDT appeared before the gamma isomer of BHC was offered commercially, and the organic phosphates followed before the BHC products had been publicized widely. The phosphates were so amazingly efficient that BHC was temporarily overlooked. However, now that the phosphates are virtually disqualified in some States many people have come to realize the superiority of the gamma isomer of BHC over DDT. It acts more quickly and with much greater certainty. The two products are combined in Pespruf-4G, making a very useful preparation. They are combined with Chlorparacide in Spraymate.

Gammexane and Gam-aphex are among the proprietary preparations of the gamma isomer of BHC (Lindane) available in Australia. They are even cheaper than DDT, especially if purchased as concentrated solutions, which may be added to other sprays, such as TMTD, wettable or colloidal sulphurs, copper oxychloride, and Chlorparacide. It is interesting to note that the tea-planters of Assam and other areas have discarded DDT in favour of Gammexane for the control of insects and caterpillars in their plantations, and of flies and mosquitoes in their homes.

Never allow Systox, E605, DDT, or Lindane on open flowers, for they are all toxic to bees.

Nicotine sulphate has been superseded for control of aphides by Lindane, DDT, and the organic phosphates. The same may be said of Clensel.

White-oil emulsion is a contact spray, and in the strength of one part to forty or fifty parts of water it is safe on roses at any time of the year, except on very hot days. It is particularly useful in dealing with the various scale insects and established mildew. It should always be mixed very carefully, and is incompatible with any form of sulphur.

Red-oil emulsion, kerosene emulsion, and Clensel are all useful contact sprays, but they are inferior to white-oil emulsion, and so are unnecessary additions to our list.

There are three types of ovicidal sprays available: E605, tar distillate, and Chlorparacide. E605 has been discussed already; in addition, it acts as a contact spray with persistent action and as a systemic poison, whereas tar distillate and Chlorparacide have no power other than as ovicides. E605 is effective against both red spider and aphis eggs, but tar distillate destroys the eggs of aphis only and Chlorparacide is useful only against red spider eggs and larvae.

Tar distillate, sometimes called Winter Wash, will destroy every aphis egg with which it comes in contact, and the presence or absence of aphides in the spring depends on the degree of efficiency shown in the application of the spray. It will burn any foliage, and so may be applied only immediately after winter pruning, while the rose plants are quite dormant. It should be handled carefully and only on perfectly calm days, for it can burn the eyes and skin severely. It is incompatible with all other sprays and spreaders.

Chlorparacide, or PCPPBS (p-chlorbenzyl p-chlorphenyl sulphide) is available in Australia as Miticide, Ovamite, and Mitox. The last of these is on sale in Britain as Chlorocide. These preparations are toxic to the eggs and larvae of red spider, but they have no effect on the adult mites or on aphis eggs. When a population containing all stages of mites is sprayed, the adult female spiders continue to lay eggs for a time. These eggs, or the larvae emerging from them, are killed by the persistent action of the deposit on the foliage. The adult mites die off naturally and are not replaced. Because of this process it usually takes two to three weeks before an active population is reduced to negligible numbers. Chlorparacide can penetrate through and diffuse across leaves, exerting persistent effect for as long as two to three months. The compound is, of course, not transferred to new growth, so that this is not protected, but red spider mites usually feed and lay eggs on the older foliage. It has no toxicity to bees or other pollinating insects, and is not dangerous to spray operators; no precautions are needed, except that one should wash well after handling Chlorparacide so as to avoid skin irritation.

Spreaders add greatly to the efficiency of sprays that show much tendency to run off foliage. The sulphonated wetting agents (especially Agral L), soapsuds, and molasses are the best spreaders. Molasses is the least efficient but is compatible with all sprays, whereas Agral L is incompatible with arsenate of lead, and soap with arsenates, lime sulphur, Bordeaux mixture, and Bordinette. Many proprietary spray preparations contain a spreading agent already.

This list of sprays is lengthy; there is no need to worry about many of them, for they overlap in their uses.

Every gardener should include in his equipment a supply of:

1.	A preparation of Lindane, or DDT, or the two in combination, or, better still, Spraymate, thus including Chlorparacide (PCPPBS).
2.	A TMTD preparation, such as Thiotox, or TMTD Fungicide.
3.	A white-oil emulsion, such as Alboleum.

For people growing large numbers of roses, the results obtained with Systox make it worth the extra trouble of complying with the regulations, but not so with people who would use only small quantities. Systox is no more dangerous than E605 but is much more efficient. It could replace the Lindane, DDT and Chlorparacide. Thus for the grower of many plants, the list is reducible to three sprays, and as two (Systox and TMTD) are compatible they can be used together at each application. In fact the Systox need be used less frequently.

For people growing fewer roses, Lindane, TMTD and PCPPBS may be applied in combination in the same way. The Lindane need be used each two weeks only in spring and autumn, and the PCPPBS is necessary only about four times between October and March. The addition of Agral L to each of the first two sprays listed will help considerably.

KARL HERBST. A vivid red Hybrid Tea show rose. Plate 50 BRIDAL ROBE. A well-formed ivory-coloured Hybrid Tea rose. Plate 51

It is very important to keep spraying materials available at all times, for they need to be used frequently, and a delay of a few days in obtaining and applying a chemical may result in vastly increased damage

Never wait for black spot or mildew to appear in your garden before you commence spraying. If you do so you will never have rose plants as healthy as you could have them by adopting a regular programme of preventive spraying. TMTD keeps the foliage so healthy that the plants appear much more vigorous, and one could believe quite readily that it acts as a fertilizer as well as a fungicide. It is not unreasonable to wait for the first appearance of thrips and aphides before using an insecticide, but do not delay once they have been seen, especially with thrips in the spring.

Do not spray only those plants that appear to be affected, for it is almost certain that any disease that is noticeable on some of the roses is present on all. Those varieties that are known to be susceptible to any particular disease, especially the fungi, are a menace to your garden, and you should avoid planting them, or discard them, unless they are needed for some special purpose.

It is essential to have a good spraying apparatus. A knapsack spray is adequate for most home gardens but there is for sale now in Australia at least one type of appliance which may be attached to the nozzle of a garden-hose for spreading spray preparations. The concentrated spray material must be in liquid form. It is put into a small barrel, which acts, in addition, as a mixing chamber. The desired degree of dilution is obtained by the setting of a simple indicator. The water-tap is turned on at much less than full pressure and the spray is controlled by means of a trigger. Its coarseness is varied by the use of one or other of several nozzles. One should not leave the water-tap turned on any longer than is necessary for the purpose of spraying because a great pressure builds up in the hose quite quickly. Spraying in this way is remarkably easy and quick and it entails the use of only one hand. The short time needed to spray a large number of roses greatly reduces the dangers involved in using organic phosphate preparations. It becomes possible, because of this speed of application, to cover a large area early in the morning before wind develops.

In recent years foliage feeding of all types of plants has received much consideration, and the results of these investigations have been very encouraging. This subject may seem too technical for many rose-growers, but in discussing sprays I may as well mention that some foliage feeding can be done along with disease control. Urea is one of the compounds used most commonly in foliage feeding; it is compatible with Systox, Lindane, TMTD, and Chlorparacide, and so it may be added to any of these sprays or to any combination of them. Only a very small quantity should be used in any one application, because all foliage feeding must be done with extremely weak solutions. It seems possible that some of the TMTD preparations already contain elements that roses absorb through their foliage, and that this, in part, accounts for the amazing health and vigour of plants sprayed with them. There are several preparations available commercially for foliage feeding. They each contain many compounds in balanced proportions. The demand for them has increased rapidly in recent years. They are sometimes called "foliar sprays".

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