Garden Pests And Diseases

GENERAL PRECAUTIONS

In all parts of the garden, pests and diseases can play havoc with the crops, whether flower, fruit or vegetable. These insect pests are divided into three classes according to the type of destruction they do and the necessary control. Those that live in the soil can only be destroyed by the use of a soil fumigant or soil sterilization. Insects that eat foliage can be killed by poison, which is usually sprayed on to the foliage and adheres as a thin film, which the insects eventually consume. The third type are those that suck plant sap and therefore cannot be killed by poisoning their food. A spray of insecticide that comes in actual contact with their bodies is the only remedy in this case.

The following are among the most common insect pests :—

Soil Pests

Carrot fly

Onion fly

Celery fly

Slugs

Millepede

Wireworms

Leaf-eating Pests

Apple sawfly

Gooseberry sawfly

Cabbage butterfly

Winter moth

Sucking Pests

Aphides

Pea and bean

Apple sucker

weevil

Woolly aphis

COMMON GARDEN PESTS

Aphis (x). On broad beans.

Damage : The tips of the beans become t4nothered with small black flies, causing istortion of the plants.

Control : Pinch out the tops of the tans and burn them. If this is done at t he first sign of trouble, no other treat-t I lent will be necessary ; but if the infestatiton has become serious, the plants must he sprayed with a nicotine solution or a burns spray.

Aphis (2). On crops other than broad beans.

Damage : These flies are not so readily seen as they are the green variety, but they cause a curling of the leaves and usually attack the growing tips of the plants first. They infest roses, and are found also on plums, dahlias and chrysanthemums.

Control : They can be destroyed in the same way as the black variety, with nicotine solution or derris spray.

Ants.

Ants will usually be found where green fly (aphis) is present.

Damage : No serious damage is done to plants. Ant nests disturb lawn surfaces and the ants themselves are a nuisance to humans.

Control : A good ant destroyer is borax mixed with plaster of paris, or sawdust soaked in paraffin. Sprinkle the mixture over the ground wherever ants are troublesome. If possible, the nest should be dug up and burnt.

Birds.

Damage: They eat the seeds.

Control :

No spraying will prevent birds from eating newly-sown seeds ; preventives must be of a mechanical nature.  For each row you require two pieces of wood I ft. wide by 6 in. to 9 in. high, two pegs made from 1 in. by 2 in. wood and 9 in. to 12 in. long, and three to four dozen nails.

Stud the largest piece of wood with the nails on three edges. Set each board in position at the end of the row and thread from end to end with black thread, starting with the lowest nail and moving up one at a time until the whole board is covered. Give the cotton a twist round each nail to prevent it slipping. When finished, the row will be covered with a black thread “ tent.” An alternative is to use small-mesh wire netting, 15 in. to 18 in. wide, arched over the rows. It is necessary to place a small piece at either end to prevent birds from getting under the arch. Otherwise netting is almost useless.

Cutworms or soil caterpillars.

These are dull green or brown in colour. When fully grown they pupate, or form a chrysalis, and turn into owlet and yellow underwing moths.

Damage : They do much by eating the seedlings off at ground level and also by eating the roots of plants.

Control : Lay baits made of paris green and bran.

Leather-jackets.

The larvae of the crane fly or daddy-long-legs are about in. to r in. long and legless, with very tough skins. In colour they are a dark brownish grey and are therefore not easily detected in the soil.

Damage : They are particularly harmful to young plants, of which in time they will eat the entire roots.

Control : Lay baits made of paris green and bran.

Millepedes.

These have long cylindrical brownish bodies with two pairs of legs on each segment and should be distinguished from centipedes, which have only one pair of legs on each segment, as the latter are of benefit to the garden. They move very fast, but curl up when disturbed.

Damage : Millepedes eat the roots of bulbs, potatoes and almost any form of vegetable beneath the soil. They bore into the flesh and ruin it for the table.

Control : The soil should be well limed and sprinkled with naphthalene. Millepedes can also be trapped in hollowed-out swedes or turnips buried just below the surface of the soil.

Slugs and snails. Damage : They eat the leaves of lettuces and other tender growth. They can frequently be traced by the slimy trail they leave behind them.

Control,: Inspection at dusk will reveal them coming out of hiding, since they only feed at night and particularly in damp weather. Thickly sprinkle lime in a ring round the plants so as to prevent slugs reaching them. Another method is to trap them in hollowed-out orange or

Wireworms.

These are yellow, with 1 hrown head and have three pairs of legs 11( ar the head.

Damage :Wireworms are usually prestit on newly broken land, in which case they are likely to be very numerous. ‘1 ‘hey attack crops of potatoes and carrots, I ly eating into the flesh of the roots and tubers.

Control: The soil should be turned equently, as they dislike aerated Boil, and this also exposes them to the ravages of birds. Lime and whizzed (I.e., finely flaked) naphthalene should also be used as against wireworms, or a trap may be employed. Bury a piece of carrot attached to a stick just under the soil and pull it up frequently, destroying all the wireworms which have collected on it.

Woodlice.

These are about ½ in. long, brownish grey, and curl up into a ball when touched. They like damp, dark situations and therefore hide under pots and boxes. They may also be found in rubbish of any kind which has been left about.

Damage: They are usually only troublesome in cold frames and greenhouses.

Control : A greenhouse kept quite clear of all rubbish is less likely to attract woodlice. They may be trapped in a hollowed-out apple and then collected and destroyed. They are also attracted by a mixture of paris green and bran.

Caterpillars.

Damage : Small holes will appear in the middle and at the edges of leaves of the cabbage tribe. If no measures are taken, these holes will gradually increase in size until many of the leaves are completely eaten away. In bad seasons they will destroy the crop.

Control : Early in the season the small yellow eggs of the caterpillar are to be found on the underside of the leaves. You can expect these when you see the white butterflies about. If you can find them remove them and burn, otherwise spray the plants with derris.

Mice.

Damage : These pests are very troublesome in some country districts, eating the seeds of peas and beans as soon as they have been sown.

Control : Before sowing, rub the peas or beans in red lead and a few drops of paraffin. Only a thin film of red lead is required. The paraffin- evaporates, leaving the seed coated. Another method is to soak the seed in a mixture of red lead and paraffin mixed to a very thin paste, and a third to put the peas in tepid water, leave them to soak overnight, put them on paper next morning, sprinkle over them a few drops of paraffin, roll well, and then roll in red lead, using a teaspoonful of red lead to a pint of peas.

Rabbits.

Damage: The havoc wrought in a garden by these pests cannot be overestimated. They will eat the green leaves of practically all plants and destroy a whole crop of seedlings in a few hours.

Control : Wire the plot all the way round with wire netting, burying it at least I ft. underground. An even better method is to allow zft. Underground, and bend the extra foot outwards away from the plot. An effective smear for trees can be made as follows : Heat raw linseed oil in a container five times the volume of the oil to be heated, and do this in the open. When it gives off a slightly bluish smoke, add 3 oz. Of powdered sulphur for each quart of oil, adding only a little at a time and then allow to get cold. It is ready for use when cold. While mixing keep it off all clothing.

PESTS, OF SPECIAL CROPS

Cabbage root fly.

Damage : The fly lays its eggs on the soil near the base of cabbages, sprouts and cauliflowers. These hatch out into maggots which burrow into the roots.

Control : Dissolve I oz. Mercuric chloride in 2 gal. Of water. This solution should be used when planting cabbages, rIi., pt. Being poured into each hole as liiting proceeds. If in previous years attacks have been severe a second water should be made ten days later. W.11 ering the seed bed with this solution ii the time of sowing is also helpful.

Carrot fly.

Damage : The fly lays its is near the roots and the maggots liii row in and feed on the carrot.

Control : The flies are attracted to the carrot by the smell, and if this is countered attacks are less likely.

Celery fly.

Damage : The fly lays its eggs in the leaf and these hatch out into maggots which burrow between the upper and lower skin of the leaf, giving it the appearance of white blisters.

Control : Celery, fly attacks the plant in the seed bed stage. Regular spraying with nicotine is necessary.

Onion fly.

Damage : The onion fly acts in the same way as the carrot fly and the maggots do much damage by burrowing into the bulb of the onion.

Control : A light .dusting with whizzed naphthalene is one method of counteracting attacks and should be used just before the seedlings are thinned out. A second application should be made about ten days later. Another method is to sprinkle with creosote mixed with sand. All seedlings removed from the crop by thinning should be burnt immediately in the compost pit.

Pea thrip

Damage : The grubs feed on the surface of the young leaves, making them turn a silvery colour. They also feed on the flowers, and as the pods develop these become twisted and turn the same silvery green colour. The affected pods are always small and misshapen. Pea thrip is more prevalent on light soils than on heavy ones and is most troublesome during May and June.

Control : As pea thrip hibernates in the soil, a soil fumigant is the most useful means of counteracting, it. The plants may also be sprayed with nicotine or derris wash.

Turnip flea beetle

Damage : These very minute beetles, which hop a considerable height when touched, eat the seedlings as soon as they appear and make lots of little holes in turnip leaves. They lay their eggs in spring.

Control : No real remedy is known. Sow the seeds thickly to allow a reasonable number of plants getting through the attack. If a rag smeared with tree-banding grease is dragged over the rows, the beetles will stick to it and can then be destroyed.

Turnip gall weevil.

Damage: The eggs are laid in the spring on the roots. The grubs hatch out and feed on the plant, causing a gall to grow in which they live. When fully fed they emerge from the gall.

Control : Strong growing plants are leSs likely to attack. Rotation of crops helps to overcome the gall weevil. All infected roots must be burnt.

Apple capsid.

Damage: Causes distortion of the fruit and leaves corky scars on the skin. Young growth stunted and whole crop may be lost.

Control: Nicotine spray before flower, buds open and at petal fall. Grease banding.

Apple sawfly

Damage: Fruit destroyed by burrowing maggot.

Control: Spray with nicotine before petal fall.

Gooseberry sawfly.

Damage: Bushes often defoliated.

Control : Spray with derris, or non-poisonous wash if fruit is formed.

Big bud mite.

Damage : Infested ,11(18 dry up, or produce distorted leaves. In it crop greatly reduced.

Control : Hand pick big buds before March. Spray lime sulphur x:13 when they are the size of a florin.

Plum aphis.

Damage : Leaves tightly lit-led, and later fall. Growth stopped .111(1 young fruits fall.

Control : Winter spraying, five per cent tar oil to kill the eggs. Spray with nicotine in spring.

Woolly aphis or American blight

Damage : Leaves, shoots and branches it tacked. The irritation of the insects’ licking causes swellings which crack and form a “ canker.” Roots also at tacked.

Control : Spray winter oil wash. Paint colonies of blight with paraffin emulsion.

Winter moth.

Damage : Young shoots and flower clusters eaten by caterpillars.

Control : Grease, banding in autumn. Spray before and after blossoming to poison young caterpillars. Female moths have no proper wings, so must crawl up the trunk.

GREENHOUSE PESTS

The greenhouse has some troublesome pests, aphis being the most common. Conditions in the greenhouse are under the gardener’s control so that he can use fumigation as well as the more usual methods of pest control.

Red spider. Damage : The insects sucking the leaves cause pale patches.

Control : The insect only thrives under dry conditions, so regular spraying with water and thorough damping down is generally sufficient. In severe cases nicotine spray can be used. Be sure to wet under the leaves as it is there that the insects lodge.- Scale. Damage : In severe cases the growth may be stunted. On palms and hard leaved plants leaves are made unsightly.

Control : Wash with nicotine and soft soap. Scrape off scales with a blunt wooden label. Once removed from the host the insect dies. Found mostly on the underside of the leaves.

White fly. Damage : Leaves much weakened by the extraction of sap.

Control : Fumigate with tetrachlorethane ; the house must be airtight.

PLANT DISEASES

Silver leaf disease.

Damage: This disease attacks plums and cherries. Infected branches show silvery foliage and wood a brown stain. It is caused by infection through wounds. It will destroy the tree if left neglected.

Control : Remove all dead wood and burn before mid-July. Cut back to healthy wood. Paint over sear with white lead paint. Give the tree a tonic of potash.

Apple and pear scab.

Damage : The two diseases are caused by different’ fungi, but the damage and control are the same. Dark spots on the leaves which spread to large patches. The disease spreads to the fruit producing scab;, spots and cracks wllich render the fruit unsaleable.

Control : Burn fallen leaves. Remove and burn diseased fruit. In winter cut out and burn all diseased wood. Spray with bordeaux mixture or lime sulphur. Care must be taken with bordeaux as it burns some varieties.

Apple canker.

Damage : Spreading cracks on the young bark. The disease gradually eats into the wood, eventually killing off whole branches.

Control : The spores of the fungus always enter the tree through existing wounds, thus by keeping down insect pests and scab the trees have more chance of avoiding infection. All dead wood must be removed and burned.

Gooseberry mildew.

Damage : A white film over the leaves and fruit which gradually turns mealy. This is h Wowed by a brown “ felt “ which also it tacks the tips of the shoots.

Control : The disease thrives in moist atmospheres. Give bushes plenty of space when planting and keep them open by :Ireful pruning. Young shoots should I re tipped in September and the diseased plant burnt. Spray with lime sulphur when the disease first appears.

Black spot on roses.

Damage: Dark ,.1 tots on the full grown leaves in midImmer. In severe cases the wood is A Ilected. Leaves fall off and the whole hush is weakened.

Control :•Burn fallen leaves. .Prune Away and burn diseased wood. Spray in .3 ‘ring with bordeaux mixture or liver of sulphur.

DISEASES OF SPECIAL CROPS

Chrysanthemum rust.

Damage: Small reddish circles on the leaves turning darker as they spread. The whole plant is rendered unsightly and is unfit for sale.

Control : Burn diseased leaves. Spray with potassium sulphide or weak lime sulphur. Dust with flowers of sulphur. The disease attacks thistles and hawkweeds so keep the garden free from such weeds. Vigorous spraying with water spreads the disease spores, so keep spraying down to the minimum until the disease is under control.

Rose mildew.

Damage: Young leaves, shoots and flower buds covered with the familiar white powder. .

Control : Spray with lime sulphur as soon as the leaves expand. Do not wait for the disease to start, especially in damp districts where the disease is prevalent. Varieties with glossy leaves are less susceptible to the disease than others. Strong, vigorous growth should be encouraged to help the bushes to resist the disease.

Club root.

Symptoms : This disease is also known as “ finger and toe.” It causes a malformation of the roots of all members of the Brassica family, which includes cabbages, sprouts, etc., and attacks turnips and radishes. The infection is carried in the soil and is very contagious.

Control : Heavy dressings of lime help to counteract the trouble, also good drainage and rotation of crops. A chemical now marketed under the name “ Brassisan “ has proved very effective, and if used according to the makers’ instructions it is non-poisonous. Seed beds should also be treated with this powder. Mercuric chloride, a poison, is an alternative remedy. Where it is known that club root is in the soil, dissolve I oz. In rzi gal. Of water, and before seed sowing water the drills with this solution, using I pt. To every 5 ft. When transplanting, pour pt. Into each hole. Destroy all infected plants.

Mint rust.

Symptoms : Orange-coloured patches appear on the leaves And stems of mint, causing distortion. Eventually the plants die down early in the season.

Control : There is little hope of curing he disease once it has made an appear.’ lice. The mint should be taken up and burnt, and a new stock started in a different part of the garden or allotment. Ti pray the vacated ground with a solution HI copper sulphide and follow this with a I rf.ssing of lime.

Pea mildew.

Symptoms : A white Itivvny mildew appears on the leaves, pi )(Is and stems, causing growth to cease pi cmaturely. It does not usually appear tin ti I the summer is well advanced.

Control : Spray the plants with liver of

Potato blight.

ymptoms : Brown plitches appear on the leaves and stems %vltich, if left unchecked, increase in size, I wcome dark in colour and gradually anse the leaves to curl up until finally the whole plant is affected, tubers and all.

Control : Success is obtained by thorough spraying with bordeaux mixture at the end of June and three weeks later. In a wet season a third spraying will be necessary. The undersides of the leaves must be wetted as well as the tops. Keeping the tubers well covered with soil prevents the spores from reaching the tubers when washed from the leaves. The rotation of crops helps.

Potato scab.

Symptoms : This fungus affects the tubers, causing brown corky spots and patches. It is more prevalent on limy and sandy soils.

Control : There are no means of discerning the trouble until the tubers are lifted. Therefore, if it is known that there is potato scab in the soil, precautions should be taken before planting. Soak the seed for two hours in a solution of formalin made by dissolving 4- pt. In 15 gal. Of water.

Potato wart disease.

Symptoms,: This disease is more likely to appear when potatoes are grown on the same land year after year. It first attacks the tubers near the eyes, causing wrinkles and warts to appear. These gradually increase in size until the tubers become a brown spongy mass.

Control : Once the disease appears there is no remedy. The simplest means to prevent the trouble is to plant immune varieties. If wart disease does appear, it must be notified to the local horticultural superintendent.

PREPARATION OF FUNGICIDES

Bordeaux mixture. Use 1 lb. Of copper sulphate and 1 lb. Quicklime to ½ gal. Of water. Lime water is made by mixing the lime with a gallon of water. The copper sulphate is mixed with the remaining water in a non-metal container. When it has completely dissolved, pour the solution into the lime water. If necessary the two solutions should be left to stand overnight before mixing to make sure that the crystals are well dissolved. Bordeaux mixture can be bought ready for use.

Cheshunt compound. Two parts finely divided copper sulphate, eleven parts fresh ammonium carbonate ; mix together and store for twenty-four hours in a tightly stoppered bottle. Use r oz. Of the mixture to 2 gal. Of water.

Lime sulphur.

A valuable fungicide for both winter and summer use. It is purchased in concentrated form , and should be used according to the instructions given by the maker.

Liver of sulphur.

This is purchased in the dry form. To make a liquid for spraying, dissolve x oz. In a gal. Of water. Must be used freshly mixed. Keep the undissolved stock in a tightly sealed vessel.

Flowers of sulphur.

Used as a dry powder when a sulphur wash is not required. Sprinkled finely over the plant, or spread with a special blower which can be purchased for the purpose.

Warning. Care should be taken with all sprays containing copper salts as they corrode metal vessels. All spray apparatus and syringes should be thoroughly washed with clear water before, being put away.

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