Eliminating Garden Pests & Diseases

Once you have spent hours of hard work and given your garden a great deal of loving care, it is disheartening to find that pests and diseases have robbed you of the pleasure of seeing perfect plants, vegetables, and fruits. So it is vital to identify your enemies and to prevent them from destroying your efforts. Good garden practice, such as winter digging, rotation of vegetable crops, hoeing, feeding, and removal of garden refuse, is the best attack. Chemical control is sensible provided you always follow the manufacturers’ instructions.

Aphids (greenfly, blackfly, also cream, grey, pink and brown) Some leaves stunted and discoloured; sticky honeydew and the presence of ants; sooty mould.: Spray with a systemic insecticide on ornamental trees, shrubs and plants and fruit trees. Use a vegetable insecticide on vegetables and soft fruit.

Beetles and weevils: Holes in brassica seedling leaves, including those of radish, swede and turnip. Scalloped edges to pea and bean leaves and also those of polyanthus. Apple buds eaten with no fruit resulting.: Spray with either a vegetable or a systemic insecticide.

Birds: Leaves of lettuce and other vegetable seedlings eaten down to ground level; flower buds eaten with no fruit resulting.: Cover crop with plastic netting.

Black spot: Yellowed areas and black blotches on rose leaves which fall prematurely.: Rake up all leaves and burn. Spray with a systemic fungicide during spring and summer. If the problem is very prevalent locally, grow resistant varieties.

Botrytis (grey mould) Leaves, stems and fruit covered with a fluffy grey mould. Fruit rots. Spray with a systemic fungicide. Keep the moisture in frames and greenhouses drier. Outside, avoid splashing water on stems, leaves and flowers.

Cabbage root fly: Maggots eat brassica roots. The plants turn bluish, wilt and often die. There is no cure, but the pests can be prevented by good soil cultivation and sprinkling a soil insecticide around each plant as a single dose between mid-spring and late summer.

Capsid bugs: Flattish insects, light brown or greenish in colour produce a speckled brownish pinhole appearance on leaves, shoots and fruit. The blooms of chrysanthemums and dahlias develop a lop-sided appearance.: Spray with a systemic insecticide.

Carrot fly: Maggots in roots.: There is no cure, but you can take preventive steps by delaying sowing until latish spring and burying all thinnings on the compost heap. You can also sprinkle soil insecticide along the seed drills before sowing and give a further dose in late spring, late summer, and early autumn if necessary.

Caterpillars: Holes eaten out of leaves in spring and summer.: Pick off by hand when first seen. Alternatively spray vegetables and soft fruit with vegetable insecticide; spray ornamental plants with a systemic insecticide.

Clubroot: Brassicas become stunted; the roots are distorted and swollen.: There is no cure, but the disease can be prevented by ensuring that the soil is rich in organic matter and well limed to prevent the acidic conditions which favour club root fungus. The planting holes can be dusted with calomel (mercurous chloride) when transplanting as a preventative measure.

Cutworms and leather jackets: Plants collapse with stems eaten through at, or below, ground level.: Hoe regularly to expose the pests to birds, frogs and toads. As a preventative measure soil insecticide can be sprinkled around seedlings and plants.

Damping off (fungus) Seedlings collapse at ground level.: Use only sterile potting mixture when raising plants in clean trays and pots. Watering with the fungicide called Cheshunt compound can prevent the infection from spreading.

Earwigs: Ragged looking foliage and chewed flower petals, especially on chrysanthemums and dahlias; cobs nibbled on sweetcorn.: Drench the plants with an insecticide.

Grubs: Holes in the fruit of apples, pears and plums, peas, raspberry and blackberry.: Spray apples in early and midsummer with insecticide to kill codling moth maggots. Spray pears with a systemic insecticide when the flower buds are white to prevent maggots (pear midge). The maggots of the pea moth can be avoided by sowing in early spring; otherwise spray with insecticide in the evening when the (lowers open and repeat ten days later. Maggots of the raspberry beetle can be prevented in cane fruits by spraying with a vegetable insecticide when the fruit first colours.

Leaf-cutter bees: Circular or semi-circular holes cut out of leaf margins on roses.: If the attack is severe, spray with insecticide. If not, ignore the problems as the bushes will soon grow new leaves.

Leaf hoppers: Mottled patches with a characteristic residue on the undersides of leaves of trees. Shrubs and especially roses.: Spray with a systemic insecticide.

Leaf miners: Irregular channels or whitish blisters on the leaves of celery. Chrysanthemums, cineraria. Holly and lilac.: Spray with a systemic insecticide: celery, late spring, early and midsummer; chrysanthemums, at fourteen-day intervals all summer; holly and lilac, late spring.

Mice: Beans, peas and bulbs fail to appear, despite adequate precautions.: Bait and set traps beneath cloches. Place rodent bait inside pieces of narrow plastic piping inaccessible to domestic animals. Plant bulbs of lilies inside guards of fine wire netting.

Onion fly: Whitish maggots burrow into the base of young onion bulbs, causing wilting and the loss of plants.: There is no cure, but sow seeds in late summer or early winter to avoid the pest. Alternatively, use onion sets which are not affected.

Peach leaf curl: Leaf curl with crimson blistering at first followed by a thickening of the foliage which turns white before falling. Almond, peach and nectarine are all susceptible. Spray with lime sulphur when the leaves are dropping in autumn and repeat again at bud burst in late winter or early spring.

Powdery mildew: Upper and lower leaf surfaces are covered with a white deposit which may cause distortion.: Roses should be sprayed regularly with a systemic fungicide to keep them clear of infection. Spray other plants when the disease is first noticed. The infection can be largely avoided by keeping the soil moist and by applying a mulch around roots in mid-spring.

Red Spider mite: Microscopic mites cause pale mottling on the leaves of greenhouse trees and plants and outdoors in summer on roses, strawberries and other plants.: Keep a more humid atmosphere in greenhouses: otherwise spray with malathion or systemic insecticide.

Root aphid: Whitish mealy pests on roots of lettuce cause the plants to will.: Surround plants with a light sprinkling of soil insecticide.

Rust: Black or rust coloured spores on the undersides of antirrhinum, carnation. Hollyhock, mint, plum and roses. Leaves fall prematurely.: Spray roses with rose fungicide regularly. Spray other plants with liquid copper fungicide and repeal weekly if necessary.

Scale insects: Tiny shell-like insects on fruit trees, ornamental trees, shrubs and greenhouse pot plants. Sooty moulds on stems.: Spray with systemic insecticide three times at fourteen-day intervals.

Slugs and snails: Leaves chewed: faint silvery trails around plants.: Keep the garden tidy and free from decaying matter. Surround susceptible seedlings and plants with slug bait.

Thrips (thunderflies) Silver mottling and severe distortion of shoots on greenhouse planis. Gladioli, onions and peas.: Spray with a systemic or vegetable insecticide.

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