Vegetable Pests and Diseases


Growing vegetables is never trouble free but if know what is wrong you have a better chance of eradicating it and, hopefully, save your affected vegetables.

This is a comprehensive article giving lots of detail on how to deal with most garden pests and diseases which affect vegetables.

Most vegetables are covered but if you need specific information about a particular crop drop me a line and I’ll add it to the article.

You can read the whole article by scrolling down or just click on the vegetable you are having trouble with:

Asparagus Aubergine Beans Beetroot
Broccoli Brussels Sprouts Cabbage Carrots
Garlic Globe Artichoke Jerusalem Artichoke Leeks
Onions Parsnips Peas Sweet Peppers
Potatoes Radish Rhubarb Spinach
Swede Sweetcorn Tomatoes (Indoor) Tomatoes (Outdoors)
Turnip      
       

 

Asparagus

Trouble

Symptoms

Treatment

Prevention

Asparagus Beetle

Stems and leaves are eaten.

Spray with liquid Derris

None

Frost

Crop turns black and dies

None

Cover the crop with fleece if frost is expected

Rust

Reddish-brown sports appear on leaves during the summer.

Remove and burn affected shoots as soon as spots appear

None

Slugs

Spears are eaten.

Sprinkle area with slug pellets or add nematodes to your soil

Keep area clear of rubbish

Spindly Spears

Thin shoots produced instead of the usual thick spears.

None

Usually caused by cutting too long into the season. Don’t harvest after mid June.

Violet Root Rot

Roots covered with purple mould, leaves turn yellow and die.

If bad start again in a new site and don’t grow root crops in the same area. If possible isolate healthy plants.

None

Wind Rock

In exposed sites roots are loosened which can lead to rotting.

None

Provide support to stems or build windbreaks around the site

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Aubergine

Trouble

Symptoms

Treatment

Prevention

Aphid

Attack developing flower-heads.

Spray as soon as attacks appear.

None

Red Spider Mite

Mottling on upper surface of leaves with tiny mites on the underside.

Spray with liquid Derris and mist leaves regularly with water

None

Whitefly

Will weaken plants.

Spray every week or two until clear

None

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Beans

Trouble

Symptoms

Treatment

Prevention

Anthracnose

Brown sunken spots on pods.

Destroy affect plants and spray remaining plants

Rotate crops

Bean Seed Fly

A soil living grub which attack seeds which then fail to germinate or produce distorted seedlings. Mainly affects early crops.

Destroy damaged seedlings

Ensure the seed bed is properly prepared and dust the drills with Chlorophos

Black Bean Aphid

Stunted growth, damaged flowers and distorted pods.

Spray at the first sign of attack and repeat if necessary

Pinch out the tops of broad beans once four trusses of pods have formed

Birds

Seeds and seedlings eaten and damage to pods and flowers

None

Place netting over crops

Botrytis (Grey Mould)

Grey velvety mould on pods.

Burn affected pods and spray remaining crop.

Spray at flowering time if this is a known problem

Chocolate Spot

Small brown spots on leaves and dark streaks along stems.

Lift and destroy diseased plants and spray remaining plants

Apply fertiliser prior to sowing and don’t sow too close together

Downy Mildew

Yellow blotches on leaves with brown mould underneath. Pods are spotted and distorted.

Spray at the first sign of disease and repeat every fortnight if necessary.

Burn affected plants after picking. Rotate crops

Foot and Root Rot

Leaves turn yellow and shrivel. Roots and the base of stems turn black and rot.

Burn affected plants and water the soil with Cheshunt Compound to avoid spreading the disease

Rotate crops

Flowers (none)

Flowers not produced.

Can be caused by disease but most likely is caused by too much nitrogen in the soil

Always use a fertiliser with phosphates and potash

Fusarium Wilt

Stunted growth. Yellowing or rolled leaves. Little crop.

Burn affected plants.

Grow wilt resistant varieties

Grey Mould (Botrytis)

Grey velvety mould on pods.

Burn affected pods and spray remaining crop.

Spray at flowering time if this is a known problem

Halo Blight

Small brown spots surrounded by a yellow “halo” on the leaves. Stunted plants.

Lift and destroy diseased plants

Never soak seed and rotate crops

Leaf and Pod Spot

Brown sunken spots on pods. Discoloured peas.

Destroy affect plants and spray remaining plants

Rotate crops

Marsh Spot

Brown-lined cavity in the centre of peas caused by shortage of manganese.

None

Add compost prior to sowing and apply a sequestered compound

Mice

Will eat seeds and seedlings.

None

Dip seed in paraffin or alum, place spiny branches along the rows or use a normal mouse trap.

Pea Aphid

Stunted growth and damaged flowers.

Spray at the first sign of attack and repeat if necessary

None

Pea and Bean Weevil

U-shaped notches at the edges of leaves. Seedlings can be killed but older plants tend to recover.

Spray at the first sign of attack

Hoe around plants during April and May to prevent further attack

Pea Thrips

Silvery patches on leaves and pods. Pods distorted.

Spray at the first sign of attack

Remove infected plants and dig over the soil before replanting

Pea Moth

Pea moth maggots burrow through pods into seeds.

None

Spray just as the flowers appear

Pods (none)

No pods develop

The loss of flowers without producing pods is often caused by birds or bees but can also be caused by roots drying out

Keep roots moist and mulch

Powdery Mildew

White powdery patches on both sides of leaves. Pods are covered in white patches.

Spray at the first sign of disease and repeat every fortnight if necessary

Burn affected plants after picking

Seed Beetle

Small round holes appear which house the seed beetle grub. Seeds don’t germinate or produce bad seedlings.

None

Buy good quality seeds and don’t plant any which show signs of holes

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Beetroot

Trouble

Symptoms

Treatment

Prevention

Black Leg

Seedlings turn black and shrivel

Remove diseased plants and water remainder with Cheshunt Compound

Sow thinly in well drained soil

Bolting

Run to seed before roots develop

None

Grow resistant varieties, don’t allow to dry out and thin seedlings as soon as possible

Fanging

Forked Roots

None

Do not add fresh manure to the soil to close to sowing and ensure the soil is stone free and well prepared

Heart Rot

Leaves wilt and brown, sunken patches on the tops of roots.

Spray repeatedly

If soil is Boron deficient add borax

Leaf Spot

Brown spots on leaves. Leaves disfigures but does not affect the crop.

None

Rotate crops

Mangold Fly (Leaf Miner)

Small white grubs burrow into leaves causing blisters.

Destroy affected leaves and spray

None

Speckled Yellows

Yellow patches between veins of leaves. Leaf edges roll inwards.

Caused by manganese deficiency so apply sequestered compound

Do not over lime the soil

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Broccoli

Trouble

Symptoms

Treatment

Prevention

Boron Deficiency

Young leaves are distorted. Brown patches on the curds.

Spray at first signs of deficiency

Apply borax before planting

Black Rot

Yellowing leaves with black veins. Will kill seedlings and mature plants are stunted.

None

Rotate crops

Cutworm

Large grey or brown caterpillars attack young plants at night and stems are severed below ground. Leaves and roots may also be eaten.

Hoe the soil around the plant during June and July and destroy caterpillars as they are found

Rake Chlorophos into the soil prior to planting

Chafer Grubs

Wilting leaves. Fat, curved grubs may be seen in the soil. The plants will die.

None

Destroy grubs as they are found during autumn digging and rake Chlorophos into the soil prior to planting

Club Root

Discoloured leaves wilt in the sun. Plants will die or grow slowly.

None

Lime well and ensure the soil is well drained. Dip transplant roots in thiophanate-methyl before planting. Rotate crops

Cabbage Caterpillars

Holes in leaves.

Spray as soon as attack appears

If white butterflies are found around the plants inspect the leaves and remove any eggs

Diamond-Back Moth

Green caterpillars fed on the underside of leaves.

Spray at first sign of attack

None

Downy Mildew

Yellowing of upper surface with white furry fungus growth beneath.

Spray at first stage of disease

Sow seeds in sterilised compost. Do not over-crowd and don’t raise seedlings where the disease has been before.

Flea Beetle

Lots of small, round holes in leaves. Seedlings can be killed.

Spray at the first sign of attack. Water plants well in dry weather.

Treating seeds with an insecticidal seed dressing will prevent early attacks

Frost

Can kill plants if it reaches the roots. Affected leaves are easily attacked by fungi or bacteria.

Burn damaged leaves

Ensure plants are firmed well when transplanting

Gall Weevil

Swellings form close to ground level. Crops are rarely affected.

Not really needed.

Apply a soil-pest killer

Leaf Spot (Ring Spot)

Brown rings on mature leaves.

Burn diseased leaves and spray

Do not plant brassicas in the same spot next season

Mealy Aphid

Waxy, greyish “greenflies” appear underneath leaves. Leaves curl and turn yellow.

Spray at the first sign of attack

Burn affected plants

Magnesium Deficiency

Yellowing between the veins of older leaves.

Apply a tonic around the plant and a fertiliser containing magnesium

Incorporate compost into the soil during Autumn digging

Manganese Deficiency

Similar in look to magnesium deficiency but tends to start on young leaves.

Apply a tonic around the plant

Incorporate compost into the soil during Autumn digging

Pigeons

Soft portion of leaves are eaten.

None

Netting is the only viable form of prevention

Slugs and Snails

Leaves and stems eaten. Young plants particularly at risk.

Use slug pellets or add nematodes to the soil

Keep the site clear of rubbish

Swede Midge

Leaf stalks near the growing point are swollen and distorted. Plant becomes blind.

Burn affected plants and spray those remaining

None

White Blister (White Rust)

White spots on leaves. Growth stunted and plants might die.

Burn diseased leaves and thin out plants to avoid over-crowding

Do not grow brassicas the following year

Wire Stem

Base of stems is black. Seedlings die.

None

Avoid growing seedlings in cold and wet soil. Avoid over-crowding

Whiptail

Thin, strap like leaves. Small cauliflower heads. Molybdenum deficiency.

Spray repeatedly

Ensure soil is adequately limed

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Brussels Sprouts

Trouble

Symptoms

Treatment

Prevention

Boron Deficiency

Young leaves are distorted and heads of cauliflowers are small and bitter. Brown patches on the curds.

Spray at first signs of deficiency

Apply borax before planting

Blown Brussels Sprouts

Open, leafy sprouts instead of tight button ones.

Remove blown sprouts

Ensure plenty of organic matter is added to the soil prior to planting and that the ground is well compacted. Ensure site is sunny and well watered.

Black Rot

Yellowing leaves with black veins. Will kill seedlings and mature plants are stunted.

None

Rotate crops

Cutworm

Large grey or brown caterpillars attack young plants at night and stems are severed below ground. Leaves and roots may also be eaten.

Hoe the soil around the plant during June and July and destroy caterpillars as they are found

Rake Chlorophos into the soil prior to planting

Chafer Grubs

Wilting leaves. Fat, curved grubs may be seen in the soil. The plants will die.

None

Destroy grubs as they are found during autumn digging and rake Chlorophos into the soil prior to planting

Club Root

Discoloured leaves wilt in the sun. Plants will die or grow slowly.

None

Lime well and ensure the soil is well drained. Dip transplant roots in thiophanate-methyl before planting. Rotate crops

Diamond-Back Moth

Green caterpillars fed on the underside of leaves.

Spray at first sign of attack

None

Downy Mildew

Yellowing of upper surface with white furry fungus growth beneath.

Spray at first stage of disease

Sow seeds in sterilised compost. Do not over-crowd and don’t raise seedlings where the disease has been before.

Flea Beetle

Lots of small, round holes in leaves. Seedlings can be killed.

Spray at the first sign of attack. Water plants well in dry weather.

Treating seeds with an insecticidal seed dressing will prevent early attacks

Frost

Can kill plants if it reaches the roots. Affected leaves are easily attacked by fungi or bacteria.

Burn damaged leaves

Ensure plants are firmed well when transplanting

Gall Weevil

Swellings form close to ground level. Crops are rarely affected.

Not really needed.

Apply a soil-pest killer

Leaf Spot (Ring Spot)

Brown rings on mature leaves.

Burn diseased leaves and spray

Do not plant brassicas in the same spot next season

Mealy Aphid

Waxy, greyish “greenflies” appear underneath leaves. Leaves curl and turn yellow.

Spray at the first sign of attack

Burn affected plants

Magnesium Deficiency

Yellowing between the veins of older leaves.

Apply a tonic around the plant and a fertiliser containing magnesium

Incorporate compost into the soil during Autumn digging

Manganese Deficiency

Similar in look to magnesium deficiency but tends to start on young leaves.

Apply a tonic around the plant

Incorporate compost into the soil during Autumn digging

Pigeons

Soft portion of leaves are eaten.

None

Netting is the only viable form of prevention

Slugs and Snails

Leaves and stems eaten. Young plants particularly at risk.

Use slug pellets or add nematodes to the soil

Keep the site clear of rubbish

White Blister (White Rust)

White spots on leaves. Growth stunted and plants might die.

Burn diseased leaves and thin out plants to avoid over-crowding

Do not grow brassicas the following year

Wire Stem

Base of stems is black. Seedlings die.

None

Avoid growing seedlings in cold and wet soil. Avoid over-crowding

Whiptail

Thin, strap like leaves. Molybdenum deficiency.

Spray repeatedly

Ensure soil is adequately limed

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Cabbage

Trouble

Symptoms

Treatment

Prevention

Boron Deficiency

Young leaves are distorted and heads of cauliflowers are small and bitter. Brown patches on the curds.

Spray at first signs of deficiency

Apply borax before planting

Black Rot

Yellowing leaves with black veins. Will kill seedlings and mature plants are stunted.

None

Rotate crops

Cabbage Stem Flea Beetle

Plants wilt and die. Small, cream grubs can be seen within the stems of cabbages.

None

Rotate crops

Cutworm

Large grey or brown caterpillars attack young plants at night and stems are severed below ground. Leaves and roots may also be eaten.

Hoe the soil around the plant during June and July and destroy caterpillars as they are found

Rake Chlorophos into the soil prior to planting

Chafer Grubs

Wilting leaves. Fat, curved grubs may be seen in the soil. The plants will die.

None

Destroy grubs as they are found during autumn digging and rake Chlorophos into the soil prior to planting

Cabbage Whitefly

Tiny white moths and larvea feed on underside of leaves. Sooty moulds develop and plants are weakened.

Spray at the first sign of attack and repeat as needed

None

Cabbage Root Fly

Blue-tinged leaves which wilt in the sun. Cabbages fail to heart and cauliflowers form small heads

Spray around the base of plants

Sprinkle Chlorophos around the base after transplanting

Club Root

Discoloured leaves wilt in the sun. Plants will die or grow slowly.

None

Lime well and ensure the soil is well drained. Dip transplant roots in thiophanate-methyl before planting. Rotate crops

Cabbage Caterpillars

Holes in leaves.

Spray as soon as attack appears

If white butterflies are found around the plants inspect the leaves and remove any eggs

Diamond-Back Moth

Green caterpillars fed on the underside of leaves

Spray at first sign of attack

None

Downy Mildew

Yellowing of upper surface with white furry fungus growth beneath

Spray at first stage of disease

Sow seeds in sterilised compost. Do not over-crowd and don’t raise seedlings where the disease has been before.

Flea Beetle

Lots of small, round holes in leaves. Seedlings can be killed.

Spray at the first sign of attack. Water plants well in dry weather.

Treating seeds with an insecticidal seed dressing will prevent early attacks

Frost

Can kill plants if it reaches the roots. Affected leaves are easily attacked by fungi or bacteria.

Burn damaged leaves

Ensure plants are firmed well when transplanting

Gall Weevil

Swellings form close to ground level. Crops are rarely affected.

Not really needed.

Apply a soil-pest killer

Heartless Cabbages

No heart in the cabbages

None

Ensure plenty of organic matter is added to the soil prior to planting and that the ground is well compacted. Ensure site is sunny and well watered.

Leaf Spot (Ring Spot)

Brown rings on mature leaves.

Burn diseased leaves and spray

Do not plant brassicas in the same spot next season

Mealy Aphid

Waxy, greyish “greenflies” appear underneath leaves. Leaves curl and turn yellow.

Spray at the first sign of attack

Burn affected plants

Magnesium Deficiency

Yellowing between the veins of older leaves

Apply a tonic around the plant and a fertiliser containing magnesium

Incorporate compost into the soil during Autumn digging

Manganese Deficiency

Similar in look to magnesium deficiency but tends to start on young leaves

Apply a tonic around the plant

Incorporate compost into the soil during Autumn digging

Pigeons

Soft portion of leaves are eaten

None

Netting is the only viable form of prevention

Slugs and Snails

Leaves and stems eaten. Young plants particularly at risk.

Use slug pellets or add nematodes to the soil

Keep the site clear of rubbish

Split Hearts

Cabbage heads split

None

Water regularly during dry weather and protect from frost

Swede Midge

Leaf stalks near the growing point are swollen and distorted. Plant becomes blind.

Burn affected plants and spray those remaining

None

White Blister (White Rust)

White spots on leaves. Growth stunted and plants might die.

Burn diseased leaves and thin out plants to avoid over-crowding

Do not grow brassicas the following year

Wire Stem

Base of stems is black. Seedlings die.

None

Avoid growing seedlings in cold and wet soil. Avoid over-crowding

Whiptail

Thin, strap like leaves. Small cauliflower heads. Molybdenum deficiency.

Spray repeatedly

Ensure soil is adequately limed

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Carrot

Trouble

Symptoms

Treatment

Prevention

Black Rot

Blackened Carrot Roots seen on stored carrots

Burn diseased roots

Store properly and do not use the same land for carrots next year

Carrot Fly

Reddish leaves which wilt in the sun. Seedlings die and mature roots are riddled with holes and will rot

None

Don’t grow near tall plants, sow thinly and destroy all thinnings

Clayburn

Not serious but will produce blackened roots

None

Dig out any clay in the soil before sowing

Carrot-Willow Aphid

Distorted, discoloured and stunted leaves and weak plants. Transmits Motley Dwarf Virus.

Spray at first sign of attack

None

Fanging

Forked roots

None

Don’t add manure or compost prior to sowing. Don’t make beds too firm

Green Top

Tops of carrots are green caused by exposure to the sun

None

Earth up around the carrots

Motley Dwarf Virus

Discoloured leaves, reduced growth and yield. Spread by Carrot-Willow Aphid.

None

Spray young carrots

Small Roots

Small carrots

None

Dig soil deeply and break up any clay by adding well-rotted manure or compost

Sclerotinia Rot

Mouldy Roots found on stored carrots

None

Ensure roots are firm and disease free before storing

Splitting

Split roots caused by heavy rain. These carrots will not store successfully

None but can still be eaten

Water regularly in dry weather and apply a mulch to conserve moisture

Swift Moth

Hollowed-out roots caused by caterpillars

None

Use Chlorophos to control

Violet Root Rot

Mouldy roots and yellowing leaves

None

Rotate crops

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Garlic

Trouble

Symptoms

Treatment

Prevention

Rust

Orange spots and blotches on surface of leaves.

None. Lift and burn affected plants

Don’t grow garlic on affected ground for three years.

White Rot (Mouldy Nose)

Foliage turns yellow and wilts. Fluffy white mould on base of bulbs and round black bodies appear in the fungus.

None. Lift and burn affected plants.

Don’t grow garlic or others from the onion family on affected ground for three years.

Top Sets

Garlic cloves form on the stalk.

Gather and use the top sets in the usual way.

This is due to changeable weather in spring so there isn’t anything to be done.

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Globe Artichoke

Trouble

Symptoms

Treatment

Prevention

Aphid

Attack developing flower-heads

Spray as soon as attacks appear

None

Petal Blight

Brown spots join together to ruin young heads

Remove and burn the affected heads

Spray as flower buds appear

Slugs

Young shoots are eaten

Sprinkle area with slug pellets or add nematodes to your soil

Keep area free of all rubbish

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Jerusalem Artichoke

Trouble

Symptoms

Treatment

Prevention

Sclerotinia Rot

Base of stems are attacked, appears as fluffy white mould

Lift and burn diseased plants. Water healthy plants with Cheshunt Compound

None

Slugs

Tubers are hollowed-out

Sprinkle area with slug pellets or add nematodes to your soil

Keep area clear of all rubbish

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Leek

Trouble

Symptoms

Treatment

Prevention

Onion Fly

Yellow, drooping leaves. Maggots burrow into the bases and kill young plants.

None. Lift and burn affected plants.

Rake Chlorophos into soil before showing or planting. Sets are less prone than seeds.

Bolting

Premature production of flower-heads.

Cut off flower stalks and lift as usual. Do not store.

Don’t sow or plant too early in the season. Ensure soil is firmed well before sowing or planting

Stem & Bulb Eelworm

Swollen, distorted foliage. Young plants die and older plants product soft bulbs.

None. Lift and burn affected plants.

Do not grow onions, peas, beans or strawberries on land previous infected with this disease.

Saddleback

On harvesting, bulbs are split at the base. Caused by heavy rain or watering after a dry period.

None. Use affected bulbs immediately.

Keep well watered during dry spells.

Set Division

Onions from sets produce twin bulbs.

None

Plant sets in good soil and keep well watered in dry spells.

Smut

Black spots and blotches on leaves and bulbs of young plants. Twisted and thickened leaves. More likely in leeks than onions.

None. Lift and burn affected plants.

Don’t grow leeks or onions on affected ground for eight years.

Rust

Orange spots and blotches on surface of leaves. More likely in leeks than onions.

Remove and burn affected leaves.

Don’t grow leeks or onions on affected ground for one season.

White Tip

Tips of leek leaves turn white and papery in autumn.

Spray with Dithane at first signs. Lift and burn badly affected plants.

Don’t grow leeks or onions on affected ground for one season.

Bull Neck (Thick Neck)

Abnormally thick necks means the bulbs will not store successfully.

None

Don’t use too much manure. Use a feed with more potash than nitrogen. Don’t sow seed too deeply.

Downy Mildew

Downy, grey mould covering leaves. Leave die back slowly and shrivel. Bulbs are soft and don’t store well.

Spray with Dithane at first signs. Repeat fortnightly.

Grow onions on a difference site each year and ensure soil is well drained.

Leek Moth

Tunnelled leaves. Caterpillars feed inside young leaves leaving the outer skin. Also attacks leeks.

Spray with a contact insecticide at first signs of attack. Destroy badly affected leaves.

None

White Rot (Mouldy Nose)

Foliage turns yellow and wilts. Fluffy white mould on base of bulbs and round black bodies appear in the fungus.

None. Lift and burn affected plants.

None. Don’t grow onions on affected land for eight years.

Shanking

The centre leaves turn yellow and collapse, outer leaves follow later. Evil-smelling slime within scales.

None. Lift and burn affected plants.

None. Don’t grow onions on affected land for several years.

Neck Rot

During storage a grey mould appears near the neck. Bulbs are soft and rotten.

None. Remove rotten bulbs.

Dist seeds and sets with benomyl before planting. Dry bulbs thoroughly before storing. Don’t store soft bulbs or bulbs with green necks.

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Onions

Trouble

Symptoms

Treatment

Prevention

Onion Fly

Yellow, drooping leaves. Maggots burrow into the bases and kill young plants.

None. Lift and burn affected plants.

Rake Chlorophos into soil before showing or planting. Sets are less prone than seeds.

Bolting

Premature production of flower-heads.

Cut off flower stalks and lift as usual. Do not store.

Don’t sow or plant too early in the season. Ensure soil is firmed well before sowing or planting

Stem & Bulb Eelworm

Swollen, distorted foliage. Young plants die and older plants product soft bulbs.

None. Lift and burn affected plants.

Do not grow onions, peas, beans or strawberries on land previous infected with this disease.

Saddleback

On harvesting, bulbs are split at the base. Caused by heavy rain or watering after a dry period.

None. Use affected bulbs immediately.

Keep well watered during dry spells.

Set Division

Onions from sets produce twin bulbs.

None

Plant sets in good soil and keep well watered in dry spells.

Smut

Black spots and blotches on leaves and bulbs of young plants. Twisted and thickened leaves. More likely in leeks than onions.

None. Lift and burn affected plants.

Don’t grow leeks or onions on affected ground for eight years.

Rust

Orange spots and blotches on surface of leaves. More likely in leeks than onions.

Remove and burn affected leaves.

Don’t grow leeks or onions on affected ground for one season.

White Tip

Tips of leek leaves turn white and papery in autumn.

Spray with Dithane at first signs. Lift and burn badly affected plants.

Don’t grow leeks or onions on affected ground for one season.

Bull Neck (Thick Neck)

Abnormally thick necks means the bulbs will not store successfully.

None

Don’t use too much manure. Use a feed with more potash than nitrogen. Don’t sow seed too deeply.

Downy Mildew

Downy, grey mould covering leaves. Leave die back slowly and shrivel. Bulbs are soft and don’t store well.

Spray with Dithane at first signs. Repeat fortnightly.

Grow onions on a difference site each year and ensure soil is well drained.

Leek Moth

Tunnelled leaves. Caterpillars feed inside young leaves leaving the outer skin. Also attacks leeks.

Spray with a contact insecticide at first signs of attack. Destroy badly affected leaves.

None

White Rot (Mouldy Nose)

Foliage turns yellow and wilts. Fluffy white mould on base of bulbs and round black bodies appear in the fungus.

None. Lift and burn affected plants.

None. Don’t grow onions on affected land for eight years.

Shanking

The centre leaves turn yellow and collapse, outer leaves follow later. Evil-smelling slime within scales.

None. Lift and burn affected plants.

None. Don’t grow onions on affected land for several years.

Neck Rot

During storage a grey mould appears near the neck. Bulbs are soft and rotten.

None. Remove rotten bulbs.

Dist seeds and sets with benomyl before planting. Dry bulbs thoroughly before storing. Don’t store soft bulbs or bulbs with green necks.

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Parsnips

Trouble

Symptoms

Treatment

Prevention

Black Rot

Blackened Carrot Roots seen on stored carrots

Burn diseased roots

Store properly and do not use the same land for carrots next year

Clayburn

Not serious but will produce blackened roots

None

Dig out any clay in the soil before sowing

Fanging

Forked roots

None

Don’t add manure or compost prior to sowing. Don’t make beds too firm

Parsnip Canker

Blackened Parsnip roots which crack leaving the root to rot

None

Lime the soil and don’t sow too early.

Small Roots

Small parsnips

None

Dig soil deeply and break up any clay by adding well-rotted manure or compost

Sclerotinia Rot

Mouldy Roots found on stored parsnips

None

Ensure roots are firm and disease free before storing

Splitting

Split roots caused by heavy rain. These parsnips will not store successfully

None but can still be eaten

Water regularly in dry weather and apply a mulch to conserve moisture

Swift Moth

Hollowed-out roots caused by caterpillars

None

Use Chlorophos to control

Violet Root Rot

Mouldy roots and yellowing leaves

None

Rotate crops

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Peas

Trouble

Symptoms

Treatment

Prevention

Anthracnose

Brown sunken spots on pods.

Destroy affect plants and spray remaining plants

Rotate crops

Bean Seed Fly

A soil living grub which attack seeds which then fail to germinate or produce distorted seedlings. Mainly affects early crops.

Destroy damaged seedlings

Ensure the seed bed is properly prepared and dust the drills with Chlorophos

Black Bean Aphid

Stunted growth, damaged flowers and distorted pods.

Spray at the first sign of attack and repeat if necessary

Pinch out the tops of broad beans once four trusses of pods have formed

Birds

Seeds and seedlings eaten and damage to pods and flowers

None

Place netting over crops

Botrytis (Grey Mould)

Grey velvety mould on pods.

Burn affected pods and spray remaining crop.

Spray at flowering time if this is a known problem

Chocolate Spot

Small brown spots on leaves and dark streaks along stems.

Lift and destroy diseased plants and spray remaining plants

Apply fertiliser prior to sowing and don’t sow too close together

Downy Mildew

Yellow blotches on leaves with brown mould underneath. Pods are spotted and distorted.

Spray at the first sign of disease and repeat every fortnight if necessary.

Burn affected plants after picking. Rotate crops

Foot and Root Rot

Leaves turn yellow and shrivel. Roots and the base of stems turn black and rot.

Burn affected plants and water the soil with Cheshunt Compound to avoid spreading the disease

Rotate crops

Flowers (none)

Flowers not produced.

Can be caused by disease but most likely is caused by too much nitrogen in the soil

Always use a fertiliser with phosphates and potash

Fusarium Wilt

Stunted growth. Yellowing or rolled leaves. Little crop.

Burn affected plants.

Grow wilt resistant varieties

Grey Mould (Botrytis)

Grey velvety mould on pods.

Burn affected pods and spray remaining crop.

Spray at flowering time if this is a known problem

Halo Blight

Small brown spots surrounded by a yellow “halo” on the leaves. Stunted plants.

Lift and destroy diseased plants

Never soak seed and rotate crops

Leaf and Pod Spot

Brown sunken spots on pods. Discoloured peas.

Destroy affect plants and spray remaining plants

Rotate crops

Marsh Spot

Brown-lined cavity in the centre of peas caused by shortage of manganese.

None

Add compost prior to sowing and apply a sequestered compound

Mice

Will eat seeds and seedlings.

None

Dip seed in paraffin or alum, place spiny branches along the rows or use a normal mouse trap.

Pea Aphid

Stunted growth and damaged flowers.

Spray at the first sign of attack and repeat if necessary

None

Pea and Bean Weevil

U-shaped notches at the edges of leaves. Seedlings can be killed but older plants tend to recover.

Spray at the first sign of attack

Hoe around plants during April and May to prevent further attack

Pea Thrips

Silvery patches on leaves and pods. Pods distorted.

Spray at the first sign of attack

Remove infected plants and dig over the soil before replanting

Pea Moth

Pea moth maggots burrow through pods into seeds.

None

Spray just as the flowers appear

Pods (none)

No pods develop

The loss of flowers without producing pods is often caused by birds or bees but can also be caused by roots drying out

Keep roots moist and mulch

Powdery Mildew

White powdery patches on both sides of leaves. Pods are covered in white patches.

Spray at the first sign of disease and repeat every fortnight if necessary

Burn affected plants after picking

Seed Beetle

Small round holes appear which house the seed beetle grub. Seeds don’t germinate or produce bad seedlings.

None

Buy good quality seeds and don’t plant any which show signs of holes

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Sweet Peppers

Trouble

Symptoms

Treatment

Prevention

Aphid

Attack developing flower-heads

Spray as soon as attacks appear

None

Red Spider Mite

Mottling on upper surface of leaves with tiny mites on the underside

Spray as soon as attacks appear and mist leaves regularly with water

None

Blossom End Rot

Brown patches at bottom of fruit

None

Water well throughout the season

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Potatoes

Trouble

Symptoms

Treatment

Prevention

Aphid

Plant infested with greenfly.

Spray at first sign of attack

None

Blackleg

Blackened stems at and below ground level. Leaves turn yellow and wilt.

None

Do not plant soft or rotten seed tubers and don’t cut tubers

Capsid Bug

Small brown spots in leaves, later turn into holes

Spray if attack is bad, will not affect yield

None

Common Scab

Ragged-edged scurfy patches. Only on the skin, the flesh is not affected.

None

Buy healthy seed tubers. Do not Lime.

Dry Rot

Shrunken area with white pustules during storage.

None

Rotate crops. Ensure tubers are sound before storing and handle carefully.

Frost

Black stems or yellow patches on leaves

None

Cover if frost is expected

Gapping

Seed potatoes do not develop shoots

None

Buy healthy seed tubers and ensure they are kept in a frost-free location

Gangrene

Dark brown depressions on the surface of the tuber

None

Store only sound tubers and keep air and frost-free

Hollow Heart

Hollow centre of tubers

None

Keep well watered during dry spells

Leaf Roll Virus

Leaves are rolled upwards and become hard and brittle

None

Buy healthy seed tubers. Spray to control the virus-carrying aphids.

Mosaic Virus

Yellow or pale green mottling over the surface of the leaf

None

Buy healthy seed tubers. Spray to control the virus-carrying aphids.

Magnesium Deficiency

Yellowing between the veins of the leaves which turns brown and brittle. Stunted growth.

Apply MultiTonic and spray with Fillip

Feed regularly during the growing season using a fertiliser with magnesium

Potato Blight

Brown patches on the leaves with white mould on the underside of each spot. Can destroy all the foliage. grey patches below the skin.

None

Buy healthy seed tubers. Spray with Dithane in July and repeat every fortnight if the weather is damp. Keep earthed up.

Potato Cyst Eelworm

Weak and stunted plants. Small tubers produced

None

Rotate crops. Don’t grow potatoes or tomatoes on infected land for at least six years

Powdery Scab

Round patches with raised margins on the skin.

None

Rotate crops

Rosy Rustic Moth

Hollow stems causing plants to die down early

None

None

Splitting

Deep cracks on surface of tubers

None

Do not store. Keep plants well watered during dry spells.

Slugs

Large holes in the tubers

None

Don’t add too much manure and lift tubers as soon as they mature. Keep the area free of rubbish.

Spraing

Curved lines in the flesh

None

Rotate crops

Soft Rot

Soft, evil-smelling flesh

None

Store only sound tubers and keep dry

Spindly Sprouts

Thin shoots

Stand tubers in a light cool place

Buy healthy seed tubers and ensure they are sprouted in a light, frost-free location.

Soft Tubers

Soft and rubbery tubers

None

Water well during drought conditions

Wireworm

Orange, shiny larvae produce tunnels in the flesh of tubers

None

Rake Chlorophos into the soil before planting and lift tubers as soon as they are mature.

Wart Disease

Black warty outgrowths on tubers

None

Only plant immune varieties on infected land

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Radish

Trouble

Symptoms

Treatment

Prevention

Brown Heart

Grey-brown rings through the flesh. Roots will be bitter. Caused by boron deficiency.

None

Apply borax before planting

Black Rot

Yellow leaves with black veins. Ring of black dots just below the skin.

None

Rotate crops and ensure the soil is well drained.

Soft Rot

Wet, slimy rot at the crown of both growing and stored crops. Can be serious.

None

Soil should be well drained and avoid adding too much manure at digging time. Rotate crops.

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Rhubarb

Trouble

Symptoms

Treatment

Prevention

Crown Rot

The terminal bud and the tissue below the crown rots.

None

Do not replant in the affected area

Honey Fungus

White streaks in the brown, dead tissue of the crown. Orange toadstools on the plants.

None

None

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Spinach

Trouble

Symptoms

Treatment

Prevention

Bolting

Premature flowering

None

Prepare the soil well and add compost and fertiliser. Plant bolt-resistant varieties

Downy Mildew

Yellow patches above and grey mould below leaves. Patches turn brown.

Pick off diseased leaves and spray at first sign of attack

Rotate crops. Ensure the soil is well drained and avoid overcrowding.

Leaf Spot

Spotted leaves.

Pick off diseased leaves and spray at first sign of attack

Rotate crops. Apply fertiliser before sowing.

Manganese Deficiency

Yellow blotches between the veins/

Apply fertiliser with manganese and spray with Fillip

Do not over lime the soil

Spinach Blight

Young leaves roll in and have a puckered, yellow surface.

None

Keep an eye on weeds and spray to control greenfly which carry the virus.

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Swede

Trouble

Symptoms

Treatment

Prevention

Brown Heart

Grey-brown rings through the flesh. Roots will be bitter. Caused by boron deficiency.

None

Apply borax before planting

Black Rot

Yellow leaves with black veins. Ring of black dots just below the skin.

None

Rotate crops and ensure the soil is well drained.

Soft Rot

Wet, slimy rot at the crown of both growing and stored crops. Can be serious.

None

Soil should be well drained and avoid adding too much manure at digging time. Rotate crops.

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Sweetcorn

Trouble

Symptoms

Treatment

Prevention

Frit Fly

The maggots bore into the growing points. Growth is stunted and small cobs.

None

Use seed dressed with insecticide or dust seedlings

Smut

Small balls (galls) appear on the cobs and stalks in hot, dry weather.

Cut off and burn the galls as soon as they appear.

Burn plants after harvest. Do not grow sweetcorn on the same site for three years.

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Tomato (Indoor)

Trouble

Symptoms

Treatment

Prevention

Blossom End Rot

Leathery dark-coloured patch at bottom of fruit

None

Don’t allow soil or compost to dry out

Blossom Drop

Flowers wither and break off

None

Water regularly and mist the flowers in the morning

Blotchy Ripening

Parts of the fruit fail to ripen

None

Control the heat in greenhouses and feed and water regularly

Buckeye Rot

Brown concentric rings around a grey spot on unripe fruit

None

Tie up lower trusses to avoid splashing. Apply a mulch.

Dry Set

Fruitlets stop growing

None

Mist plants twice a day with water

Eelworm

Stunted growth. Discoloured and wilted leaves. Tiny white cysts on roots.

None

Don’t grow tomatoes or potatoes in infested soil for at least six years.

Foot Rot

Stem bases are brown. Tends to affect seedlings.

None

Use sterilised soil or compost to raise seedlings. Don’t over water.

Greenback

The area around the stalk remains green and hard

None

Provide shade to greenhouses to control the heat. Feed regularly.

Ghost Spot

Grey mould spores fall on fruit leaving ‘water spots’

None

Provide good ventilation. Control Grey Mould and do not splash fruit when watering

Greenhouse Whitefly

Tiny moths on underside of leaves. Leaves are pale and curled. Sticky fruit with black mould.

Spray at first sign of attack

None

Grey Mould

Grey mould appears on damaged stems and can spread

Cut out diseased area

Ensure adequate ventilation, avoid over crowding and remove decaying leaves and fruit.

Hormone Damage

Fern-like and twisted leaves. Twisted stems and stalks.

None

Ensure lawn weed killer does not come in contact with plants

Hollow Fruit

Hollow fruit

None

Avoid too much heat or cold. Water regularly. Ensure adequate potash in the soil.

Leaf Roll

Rolled leaves is not a bad sign in young leaves as long as they are dark green. In older leaves it may be due to side variations in day and night temperatures. Provided no pests are present then no action is required.

Magnesium Deficiency

Yellowing between veins of leaves. Starts on lower leaves and moves up.

Use a foliar spray containing magnesium

None

Potato Blight

Bark brown blotches on leaves. Brown, shrunken areas on fruit. May develop during storage.

None

Tomatoes grown under glass are not always infected but to prevent a likely attack or for outdoor tomatoes use a protective spray of mancozeb (Dithane) or copper (Murphy Traditional Copper or Vitax Bordeaux Mixture). Try to apply these before the symptoms are seen but if this isn’t possible use as soon as possible. They will not totally prevent infection, but often slow it sufficiently to save the crop.

Root Rot

Roots are brown and corky. Plants wilt in hot weather.

Mulch to encourage new roots

Use new soil or fresh compost

Sun Scald

Pale brown, papery-skinned depression on side of fruit facing greenhouse glass

None

Paint glass and damp down well. Do not mist plants at mid-day.

Split Fruit

Fruits split

None

Keep roots moist

Stem Rot

Stem bases are brown. Tends to affect mature plants.

None

Sterilise greenhouse and equipment

Tomato Leaf Mould

Purple brown mould patches on underside of leaves, yellow patches on upper side. Lower leaves attacked first.

Remove some of the lower leaves and spray at first sign of attack.

Ventilate greenhouse at night

Tomato Moth

Large, green or brown caterpillars tunnel into fruit and stems.

None

Spray when small caterpillars holes appear in leaves

Virus

Mottled and curled leaves. Dark vertical streaks on the stems. Stunted growth. Mottled and bronzed fruits.

None

Buy virus-free plants. Spray to control greenfly

Verticillium Wilt

Leaves wilt in hot weather. Lower leaves turn yellow. Brown streaks through the stem tissue

Mulch around stem to encourage new roots.

Don’t grow tomatoes in infected soil

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Tomatoes (Outdoors)

Trouble

Symptoms

Treatment

Prevention

Blossom End Rot

Leathery dark-coloured patch at bottom of fruit

None

Don’t allow soil or compost to dry out

Blossom Drop

Flowers wither and break off

None

Water regularly and mist the flowers in the morning

Blotchy Ripening

Parts of the fruit fail to ripen

None

Control the heat in greenhouses and feed and water regularly

Buckeye Rot

Brown concentric rings around a grey spot on unripe fruit

None

Tie up lower trusses to avoid splashing. Apply a mulch.

Dry Set

Fruitlets stop growing

None

Mist plants twice a day with water

Eelworm

Stunted growth. Discoloured and wilted leaves. Tiny white cysts on roots.

None

Don’t grow tomatoes or potatoes in infested soil for at least six years.

Foot Rot

Stem bases are brown. Tends to affect seedlings.

None

Use sterilised soil or compost to raise seedlings. Don’t over water.

Hormone Damage

Fern-like and twisted leaves. Twisted stems and stalks.

None

Ensure lawn weed killer does not come in contact with plants

Hollow Fruit

Hollow fruit

None

Avoid too much heat or cold. Water regularly. Ensure adequate potash in the soil.

Leaf Roll

Rolled leaves is not a bad sign in young leaves as long as they are dark green. In older leaves it may be due to side variations in day and night temperatures. Provided no pests are present then no action is required.

Magnesium Deficiency

Yellowing between veins of leaves. Starts on lower leaves and moves up.

Use a foliar spray containing magnesium

None

Potato Blight

Bark brown blotches on leaves. Brown, shrunken areas on fruit. May develop during storage.

None

Use a protective spray of mancozeb (Dithane) or copper (Murphy Traditional Copper or Vitax Bordeaux Mixture). They will not totally prevent infection, but often slow it sufficiently to save the crop.

Root Rot

Roots are brown and corky. Plants wilt in hot weather.

Mulch to encourage new roots

Use new soil or fresh compost

Split Fruit

Fruits split

None

Keep roots moist

Tomato Moth

Large, green or brown caterpillars tunnel into fruit and stems.

None

Spray when small caterpillars holes appear in leaves

Virus

Mottled and curled leaves. Dark vertical streaks on the stems. Stunted growth. Mottled and bronzed fruits.

None

Buy virus-free plants. Spray to control greenfly

Verticillium Wilt

Leaves wilt in hot weather. Lower leaves turn yellow. Brown streaks through the stem tissue

Mulch around stem to encourage new roots.

Don’t grow tomatoes in infected soil

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Turnip

Trouble

Symptoms

Treatment

Prevention

Brown Heart

Grey-brown rings through the flesh. Roots will be bitter. Caused by boron deficiency.

None

Apply borax before planting

Black Rot

Yellow leaves with black veins. Ring of black dots just below the skin.

None

Rotate crops and ensure the soil is well drained.

Soft Rot

Wet, slimy rot at the crown of both growing and stored crops. Can be serious.

None

Soil should be well drained and avoid adding too much manure at digging time. Rotate crops.

Turnip Mosaic Virus

Young leaves are twisted and mottled. Dark green, raised spots on the leaves. Young plants can die.

None

Spray to control the greenfly carrier

I have also produced this article in PDF format for you to download, keeping it handy to refer to: Vegetable Pests and Diseases Easy Guide

To open this file you need Adobe Reader. This is a free application which may already be on your computer. If it isn’t you can download a copy for free here.

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