Identifying and Controlling Garden Pests

Pests in the garden are of several types, and as every gardener knows they are almost unlimited in number. They can however, be grouped according to type, which makes their destruction easier. Some pests live underground for part or all of their lives: housewives are too familiar with the insects that inhabit potatoes and other root crops. Others climb or fly to the upper parts of the plant and attack leaves.

The following lists of some more common garden pests help the gardener in identifying garden pests and show the gardener the damage caused and methods to control these pests.

Information on following garden pests is provided here:

  • Cuckoo Spit Insects
  • Earwigs
  • Flies
  • Leaf Cutting Bees
  • Leaf Miners
  • Mealy Bugs
  • Millipedes
  • Mites

Cuckoo Spit Insects

These pale green of yellow nymphs are the larvae of the common froghopper. They produce frothy spittle like masses on the leaves and shoots of roses, campanulas, geums, lavender, rudbeck and solidago. Inside these deposits are the larvae that suck the sap and cause wilting of leaves and malformation of young shoots. They are not serious pests.

Destroy by syringing first with clear water to remove the froth, then with derris or nicotine to kill the larvae.

Earwig Insect
Earwig Insect

Earwigs

In damp, warm weather these insects will sometimes attack cauliflowers, dwarf beans, cucumbers and tomatoes , and the flowers heads of chrysanthemums, dahlias and French marigolds. In the garden, earwigs seldom do severe damage, though occasionally they may completely strip the foliage. In the greenhouse, they can cause serious damage to flower heads, and their presence is seldom discovered until the damage is done.

If damage in the greenhouse is persistent, dust with DDT or BHC round the area of attack and on the floor. Keep the garden clear of rubbish, which provides shelter for earwigs.

Cabbage root fly larvae
Cabbage root fly larvae

Flies

Cabbage root flies

The white larvae of these flies tunnel into many root vegetables, such as turnips, Swedes, and radishes, making them useless. The larvae also attack the roots of newly planted cabbage and other brassica seedlings; the plants turn a bluish color, wilt and die.

To control, apply gamma-BHC round the base of the plants in late April, and within four days after transplanting seedlings; or dip the seedlings in calomel paste before planting them in their permanent positions.

Carrot fly larvae
Carrot fly larvae

Carrot fly

The larvae tunnel into the carrot roots. Symptoms of damage are reddening and wilting of the foliage. In dry weather seedlings may be killed.

Before sowing, dress the seeds with lindane and dust the seed drills with gamma-BHC; alternatively, spray or dust the seedlings with DDT.

Celery fly damage
Celery fly damage
Celery fly larvae
Celery fly larvae

Celery fly

The small white larvae of these flies are the most serious pests of celery, and may also attack parsnips. They burrow into the leaves, stunting the growth of stalks and hearts.

Spray or dust seedlings with DDT or malathion. With severe attacks, continue to apply at regular fortnightly intervals until August.

Leatherjackets
Leatherjackets

Leatherjackets

There large, earth colored grubs are the larvae of cranefly or daddy-long-legs. They feed on the roots of grass, particularly in lawns, causing the whole areas to grow weak and thin. Many plants in the herbaceous and vegetable gardens are also attacked by leatherjackets, especially after a wet autumn, as they need damp conditions to survive in winter.

Digging and hoeing the soil, destroying weeds, and filling in or draining low-lying places are effective cultural methods of control. Chemical control consists of treating the infested soil with DDT or gamma-BHC dust from mid October to April. Crude naphthalene is also effective, if worked into herbaceous border at the rate of 2-3 oz. per square yard. Water the lawn thoroughly with a liquid DDT solution.

Narcissus fly larvae
Narcissus fly larvae

Narcissus fly

Larvae, emerging from eggs laid near the necks of such bulbous plants are daffodils, narcissi, lilies and hyacinths, burrow into the bulbs and feed inside. Bulbs lifted with larvae inside have a soft skin, and should be burnt immediately. Spray or dust the bulb necks with BHC or DDT at weekly intervals until the end of June.

Onion fly larvae
Onion fly larvae

Onion fly

The larvae of these flies burrow into the bulbs of young onions and shallots, causing the plants to wilt and reducing the bulbs to pulp. Destroy the attacked plants immediately, and dust the surrounding soil with calomel or gamma BHC. To prevent attacks, dust the onion sets with these insecticides before planting. If you are raising them from seed, dust the seed drills and the young seedlings.

Pea midge larvae
Pea midge larvae

Pea midges

The minute larvae are common on pea flowers and the inner surface of the pods, spoiling the quality of the crop. Routine application of DDT to control pea moths and weevils will also kill off pea midges.

Leaf Cutting Bee
Leaf Cutting Bee

Leaf Cutting Bees

These insects resemble hive bees. They damage the foliage of roses, also sometimes of laburnums, lilacs and rhododendrons, by cutting small pieces from the leaves and using them to line their nests. Severe damage is seldom caused. There is no chemical control. If damage is serious, the nests  should be traced and destroyed.

Damage caused by Leaf Miners
Damage caused by Leaf Miners

Leaf Miners

These larvae of several species of insects feed on the tissues between leaf surface of beet, celery and occasionally parsnips. Tomatoes and many pot plants under glass may also be attacked, as well as chrysanthemums and cinerarias.

In severe cases whole leaves may be destroyed. The adult flies appear from April onwards and lay eggs on the underside of the leaves. The larvae or  grubs mine or tunnel between the upper and lower surfaces, causing white wavy marks on the foliage.

Spray with DDT , BHC or a combination as soon as the damage is seen, and in severe cases repeat at fortnightly intervals. Malathion with DDT or nicotine are alternatives. In greenhouses, use smoke containing BHC or DDT on cucumbers or melons.

Mealy Bug Zoomed
Mealy Bug Zoomed
Plant infested with mealy bugs
Plant infested with mealy bugs

Mealy Bugs

These pink or yellow insects related to the scale insects are common in green houses, where they feed on the leaf sap or roots or a wide range of plants. The bodies of bugs are covered in a white wax; and their presence in the greenhouse is often denoted by snooty deposits on leaves. If not controlled they will spread rapidly, since they can breed throughout the year if the conditions are right for them under glass. Outdoors they infest flowering currants, ceanothus and laburnum.

Control is not easy, as they multiply rapidly under greenhouse heat, and the waxy coat is difficult to penetrate without a powerful spray. Apply tar oil during dormant seasons, where this is possible. It may be necessary to fumigate the greenhouse to dislodge the pests from curled leaves and leaf axils. In the growing season spray with nicotine, white oil or malathion.

Millipedes
Millipedes

Millipedes

These long, black, slow-moving creatures, with numerous legs, live in the soil. They feed on all vegetable matter, both dead and living and so do extensive damage by tunneling into seeds, gnawing roots and chewing into tubers and bulbs, particularly lilies. They also extend the damage already done by slugs and snails, and prepare the way for attacks by fungi and bacterial diseases.

Control is not easy. Bait such as hollowed out potatoes can be sunk just below the surface, crude naphthalene can be incorporated into the top spit of soil, or DDT can be dusted along the drills to protect young seedlings. Continuous hoeing to keep the soil disturbed will also help.

Mites

Microscopic creatures related to the spider family. Certain species are harmful pests in the garden they produce as many as seven generations during a hot, dry summer and unless controlled may cause a drastic reduction of crops. Certain insecticides which are lethal to true insects have no effect on mites and may even help to increase their numbers by killing off insect predators on the mites.

blackcurrant gall mite damage in blackcurrant bud
blackcurrant gall mite damage in blackcurrant bud
blackcurrant gall mite
blackcurrant gall mite

Big bud mite (black currant gall mite)

These mites live in black currant leaf buds, which swell to an abnormal size and eventually wither and fall off. Red and white currants may also be affected, but the buds do not swell before they die off.

It is important to control these mites, as they are responsible for the spread of virus disease known as reversion, which causes a rapid weakening of the plants. Spray with lime-sulphur at grape stage, just before the blossoms open. Some varieties of black currants are sulphur-shy, and should be sprayed with a weaker solution. If the bushes are badly attacked, they must be dug up and burnt.

serrated leaf due to bulb scale mite.
serrated leaf due to bulb scale mite.

Bulb scale mite

These extremely small creatures infest the scales and young leaves of bulbous plants, such as daffodils, narcissi, and amaryllis, particularly those that are being forced or stored under warm conditions. Brown patches may be seen between the scales when the bulbs are lifted; other symptoms of attack are rust colored streaks on foliage and flower stalks, poor blooms and weak growth.

Always lift blubs carefully to avoid splitting the skins, and store under cool conditions. Control the mites by immersing infested dormant bulbs in warm water at a temperature of 43°C (110°F) for one hour.

Fruit tree red spider mite eggs
Fruit tree red spider mite eggs

Fruit tree red spider mite

The minute eggs are laid on the bark and young shoots of fruit trees such as apples, pears, plums and quinces. When present in large numbers, the mites cause extensive damage to the foliage by feeding on the sap. In a bad attack, the leaves turn bronze and drop prematurely.

Destroy the eggs with a petroleum winter wash before bud break, or spray in summer with derris, malathion or dimethoate. Lime-sulphur sprays, used to control scab on apples and pears, are also effective against red spider mites, but should be used only on apples which are not sulphur shy.

Gooseberry red spider mite

These pests chiefly suck the sap of gooseberry leaves, and related species infest other plants. The foliage turns pale or bronze red, and fruits do not develop. Apply derris, nicotine, malathion, or dimethoate after petal fall. If necessary, repeat two weeks later.

red spider mite
red spider mite

Greenhouse red spider mite

These are serious pests of many plants grown under glass. They attack tomatoes, melons, chrysanthemums, carnations, grapes, orchids and pot plants. The mites suck sap from the foliage, causing a severe check on growth and vigor.

Effective chemical controls include the use of smokes or aerosols containing azobenzene and nicotine. Derris , malathion, and dimethoate may also be applies, as a wet spray or in aerosol form. Red spider mites dislike damp conditions: keeping the roots moist and regularly watering the foliage will help to prevent serious damage.

Strawberry mitemite
Strawberry mitemite

Strawberry mite

In April or May these creatures may attack strawberry foliage, causing it to shrivel and turn yellow. Spray of dust with a non persistent insecticide such as derris or nicotine when the air temperature is above 16°C (61°F). A late attack after harvesting is best controlled by burning off the leaves.

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