aphids

'Aphids' is a generic term for over 500 species (in the UK) of sap-sucking insects which secrete honeydew. The moulds that often grow on this are unsightly, but generally harmless. However, the aphids do weaken plants and distort growth and leaves. More seriously, aphids transmit many viruses and the physical wounds they cause encourage further infections.


Symptoms

  • Distorted growth & leaves
  • Discarded white exoskeletons on tops of leaves
  • Sooty and/or sticky patches on leaves
  • Presence of ants which may protect the aphids in return for the honeydew they produce
asparagus beetle

These small (6-8mm long) beetles are either black with six yellow spots (common asparagus beetle) or orange with black spots (spotted asparagus beetle). The adults eat emerging spears during the spring, lay eggs and then the larvae eat the stems and foliage.


Symptoms

  • Holes and yellow or brown discolouration in emerging asparagus tips
  • Whole spear may die if damage severe
big bud mite

Also known as Gall mite, this microscopic (1/4 mm long) white mite lays its eggs in buds from June until spring. Many thousands of mites can infest each bud. As they suck sap from the developing leaves, they cause the bud to change shape and swell, sometimes forming galls. By the spring, the buds may be dry and leaves fail to emerge.

From April until July, the mites emerge from infected buds and then spread to surrounding buds and plants, often transported by passing insects, by wind or even rainsplash. The blackcurrant's relatives, gooseberries and redcurrants are also affected but without the chatacteistic big buds.

Yields may be reduced but far more important than it's direct effects is the fact that the mite transmits reversion virus.

Symptoms

  • Enlarged buds from late summer:
    • spherical appearance unlike the normal pointed appearance of buds
    • up to twice the size of normal buds by autumn
    • most visible when leaves have fallen in the autumn
  • Buds may turn into galls
  • In spring buds fail to open or leaves are stunted
birds

Pigeons and other birds can quickly strip the tender parts of crops, demolish berries and pull up sets. Severe attacks can leave you with no crop but, before you make your allotment a bird-free zone, don't forget that birds are a vital part of integrated pest control.


Symptoms

  • Brassicas and peas stripped leaving little but the tough stems and veins
  • Bush fruit such as currants and tree fruit, especially cherries, either removed completely or left half-eaten.
  • Onion sets pulled from the soil and left scattered about
blackfly/black bean aphid

An aphid which affects members of the bean family, stunting growth, distorting leaves and pods and, if left unchecked, reducing yields.


Symptoms

  • Distorted leaves and stem
  • Stunted growth
  • Mass of black insects at growing points
blight

A serious disease which affects first the top leaves, with brown blotches in late summer, in warm, wet weather. More often than not, the fungus then spreads down the stems killing the foliage.


Symptoms

  • Brown spots which begin on upper leaves
  • Brown patches on tubers, firm at first but quickly turning to a soft, wet rot
blossom end rot

A sunken, dark patch at the end of fruit where the petals were indicates calcium deficiency. This causes cells to swell and burst. As a lack of calcium in soil or compost is rarely a problem, it is almost always due to inadequate distribution of that calcium around the plant by water - either because of insufficient water at the roots or too little transpiration (loss of water through the leaves).


Symptoms

  • A dark (yellow, green, brown or black), often sunken, patch at the end of the fruit where the flower was
  • Tends to affect the earliest trusses and larger fruited varieties more seriously
bolting

Plants are said to 'bolt' when they start flowering before you have had a chance to harvest the roots or leaves that you are growing the plant for. This concentrates the plant's resources on the flower and often leads to toughness or bitterness.


Symptoms

  • Vary from crop to crop but, generally, one or more fast-growing spikes of growth appear which show signs of flower formation
cabbage root fly

This innocuous-looking fly lays its eggs on the soil surface near brassica roots. When they hatch, the 6-8mm long maggots begin eating the roots. The maggots go through a brown pupal stage before emerging as adults, mating, and infecting new plants. There are typically three generations every year, with the pupae of the third generation overwintering in the soil, emerging in the spring to begin on a new crop.


Symptoms

  • Leaves may have a bluish tinge
  • Damage to the roots means that plants tend to wilt in dry weather and can be pulled up easily
  • Growth will be reduced and seedlings and young plants may die
  • Brassicas grown for their roots may be totally unusable
  • The white maggots are often clearly visible when the roots are examined
cane spot

This fungal disease can be a serious problem in raspberries, hybrid berries and blackberries. Spots first appear in May and June then travel up the plant. The purple spots grow like fairy rings, leaving dead cells in a depression as they expand. Infections which overwinter on last years' canes will infect the following year's new growth unless checked.


Symptoms

  • Purple spots on lower parts of stems
  • Spots grow and spread upwards, leaving silvery-white depressions with purple margins - typically elliptical on stems and circular on leaves.
  • Leaves and fruit may be distorted and leaves may die back
  • In severe cases, plant may die
capsid bug

Despite giving plants a ragged appearance and, in severe cases, causing some die-back of leaves and deformation of fruit, this is rarely a serious disease. This is just as well as the bugs are often long gone by the time the damage is noticed, and they are quick-moving, dropping to the ground when disturbed - this makes control difficult. Adults are green and about 6mm long, with wings which make a distinctive diamond pattern when folded. The nymphs are wingless and paler in colour. Eggs hatch in April (2nd generation in early/midsummer). The nymphs feed on woody plants for a few weeks before moving on to surrounding herbaceous plants, pupating, emerging and laying more eggs on woody plants - it is as eggs that they overwinter. Like aphids, they suck the sap from the growing parts - shoot tips, buds, young leaves and flowers - of the plant. Unlike aphids, however, they inject a toxin which kills surrounding cells, leaving brown edges. As the leaves grow, these holes expand and tear.


Symptoms

  • Small holes in young, growing parts of the plant, particularly young leaves
  • As leaves expend, brown-edged holes which may tear
  • Flowers and fruit may be deformed
carrot fly

This small black fly, which only flies low to the ground, lays its eggs around the roots of any of this family of crops, generally from mid-April until the end of May and from mid-July until the end of August, although there may be three generations in some areas.

The maggots emerge about a week later and begin feeding on the roots, smaller ones at first, before moving into the main tap root. They tunnel through the root which turns brown where soil enters the tunnels, either emerging as adults immediately or overwintering.


Symptoms

  • In some cases, the leaves take on a reddish tint and growth may be stunted
  • Roots are ringed with brown tunnels, often containing the white or cream maggots which are around 1cm long
  • The damage caused may allow secondary infections to cause further damage
  • Damage is generally most serious in carrots
caterpillars

Caterpillars can very quickly cause considerable damage to crops, particularly brassicas. They are the larval stage of butterflies and moths - on brassicas, normally the large white (Pieris brassicae) , the the small white (Pieris rapae) or the cabbage moth (Mamestra brassicae).


Symptoms

Aside from the caterpillars themselves which reach 3-4cm in length and can be very numerous:
  • Yellow eggs on the undersides of leaves
  • Holes in leaves
  • Dark droppings at the base of leaves where they collect
celery leaf miner

Small (5mm long) white maggots 'mine' tunnels through the leaves, leaving brown blotches and blisters. Up to three generations each year mean an attack can come at any time from late spring onwards. These can cause stunted growth and bitterness.


Symptoms

  • Long silvery trails along leaves
  • Stunted growth
chocolate spot

As the name suggests, this fungus (and, less commonly, its relative Botrytis cinerea) causes small red/brown spots on leaves and streaks on stems. The disease progresses rapidly in damp conditions, when the spots enlarge and spores are released, spreading the infection to other plants. In serious cases, the spots merge and darken, and may cause stems to collapse and even kill the plant.


Symptoms

  • Red/brown brown spots, sometimes with a white/grey centre as they expand, on all parts of the plant
  • Shrivelled and dropped leaves and flowers
  • In severe cases, collapsed stems
club root

A serious disease which infects the roots, causing swelling and distortion as it creates a gall from which spores are eventually released. This fungus-like organism, related to powdery scab in potatoes, leads to poor growth and even death.


Symptoms

  • Poor growth
  • Foliage wilts in dry weather, recovering when wet
  • Foliage discoloured - purple tinge
  • Roots swollen and distorted
crown rot

The collective name for a variety of fungi and bacteria which attack the base of the leaves and the crown, where new leaves are formed.


Symptoms

  • Soft brown/black areas around the crown
  • Yellowing leaves
  • Weak/collapsing stalks
cucumber mosaic virus
This serious viral disease affects, and may even kill, a surprising number of different vegetables and flowers. It is usually spread by aphids but can also be spread by contact. It survives between crops in other hosts, usually weeds.

Symptoms

  • Distinctive light green/yellow and dark green mosaic pattern on leaves
  • Leaves may curl downwards
  • Fruit become misshapen, knobbly and pale, even white
  • Growth is stunted and the plant may eventually die
cutworm

These are the caterpillars, 20-50mm long, of two species of noctuid moth - Agrotis ypsilon (greasy cutworm) and Agrotis segetum (turnip moth) which attack the stems of seedlings and young plants at ground level at night.

Females lay the eggs on all parts of the plant. A fortnight later, the caterpillars emerge, feeding on the leaves for a fortnight before moving into the surface layer of the soil. They feed here for a month or two before pupating in the soil to emerge as moths a fortnight later.

They are more common in dry, light soil and can be seen in the soil around the plants at night and can be recognised by the way they bend into a crescent ('C') shape when disturbed.


Symptoms

  • Sudden wilting through partial damage or even complete severing of the stem at soil level.
downy mildew
A range of species of fungus, each of which may only have a limited range of hosts, but which manage to infect a very wide range of edible and ornamental plants. The fungus spreads by airborne spores and thrives in conditions when leaves are damp. It is most serious on lettuce, where it can kill whole leaves, and onions, where the leaves die back and the bulbs can rot, preventing storage.

Symptoms

  • Discoloured, often yellow (but also brown, purple or pale green) patches on the surface of leaves. Infections on other parts of plants are less common but pea pods are sometimes affected
  • Corresponding grey (lettuce), white (brassicas) or purple (legumes) mouldy/furry patch on the underside.
  • Weak or stunted growth
  • Leaf die-back or fall
flea beetle
These small, shiny beetles, which quickly abandon ship if disturbed (they jump with strong hind-legs like fleas...hence the name), can be a serious pest of seedlings, in particular, although they can still check the growth of larger plants. The adults eat the surface of leaves while the larvae eat the roots, although the latter causes little damage.

Symptoms

  • Small, round(ish) holes appear in the middle and at the edges of leaves. They may not go all the way through the leaf and are generally smaller than those caused by slugs
frost
Frost defines the beginning and end of the main vegetable growing season, except for those plants which can tolerate it. That said, many plants will cope with a light frost early in the season and, if not killed, most recover well. In contrast, at the end of the season, frost can damage fruit such as pumpkins and courgettes so that they most be eaten immediately or rot.

Symptoms

  • Brown edges or whole brown leaves appearing overnight
  • Darker, almost translucent patches on pumpkins, courgettes and squash
gooseberry sawfly

A serious pest of gooseberries and its relatives, red and white currants, which can strip all of a bush's leaves down to the veins in a matter of days in serious cases. While this won't necessarily kill the plant, it will seriously affect yields and encourages disease.

The adult emerges in April and lays its eggs, often along the veins on the underside of the lower leaves in the centre of the plant - just where it is hardest to spot them. The eggs hatch and the larvae, which eventually reach 2cm long, emerge. They look very much like caterpillars - pale green with black spots and a shiny black head - but have more back 'legs' than butterly and moth caterpillars. They feed first low down, at the centre of the plant, before spreading outwards and upwards. Within a month they will have grown to full size. They then drop to the soil and form a cocoon from where the next generation emerges - there may be three or four of these a year.


Symptoms

  • Very pale green, 1mm long eggs laid on the undersides of leaves near the bottom of the plant
  • Tiny holes in leaves near where the eggs have hatched
  • Larger holes further up and towards the ouside of the plant follow
  • In severe cases, complete defoliation
green top
Sunlight hitting the shoulders of carrot roots causes the chlorophyll to turn the tops green. This won't help you win any vegetable shows but has no effect on edibility.

Symptoms

  • Carrots have green tops where sunlight has got to them
grey mould
This fungus thrives in cool, damp and over-crowded or badly-ventilated conditions. Almost any crop can be affected. The fungus generally enters through existing wounds and healthy plants are less likely to be affected.

Symptoms

  • Generally start with a brown rot followed by the grey fluffy mould which gives it its common name
  • Lettuce commonly show a reddish-brown colour and the leaves may break away from the roots
  • Tomatoes may show spots on the surface
leek moth
This innocent looking brown (c. 10mm long) moth has been spreading West and North in recent years and laying eggs on the allium family of crops. The light/yellow-green caterpilars grow to 10mm or so while tunneling through the leaves, and sometimes into the 'bulb'. There are two generations a year with attacks in late spring and late summer. If the damage caused doesn't allow other infections in, leeks often recover, producing an edible, if reduced, crop, but onions tend to die.

Symptoms

  • Light yellow/brown patches on leaves
  • Yellowing/twisted leaves
magnesium deficiency
Magnesium is a key component of chlorophyll - the pigment which absorbs the energy from light (it also gives plants their green colour as green light is less well absorbed so this is what we see) to be used in photosynthesis. Affected plants will try to ensure that new leaves have enough chlorophyll so will move it from older leaves. Soil acidity (low pH) is the usual cause but the use of high potassium (potash) fertilisers also make magnesium unavailable to plants as it may be taken up in preference and nutrient-poor sandy soils may also suffer.

Symptoms

  • Yellow, orange, red or purple areas between leaf veins affect lower/older leaves first
  • These leaves may then turn brown and die
  • Reduced photosynthesis leads to stunted growth and lower yields
mice
Mice take larger seeds, even when they have recently germinated. They will also take the seeds of mature vegetables. They are more likely to bother gardeners in the autumn and early spring when other food is scarce.

Symptoms

  • Seeds appear to have failed to germinate
  • They sometimes leave a small hole from their burrowing
  • On pea pods and sweetcorn cobs, look for tell-tale ragged teeth marks
onion fly
The onion fly looks similar to a house fly but is grey and slightly smaller. It overwinters as a pupa in the soil and emerges around May/June, mating quickly and laying eggs on or around onion seedlings. The white maggots then burrow into the bottom of the bulb, where they grow to 8mm or so long, as they carve out tunnels. They will travel from one onion to another as they grow and after about three weeks, move back into the soil and pupate. Three weeks later, the next generation hatches leading to continued attacks, albeit of decreasing severity, from July to September. Growth is stunted and badly affected plants may die. The tunnels are unsightly but are often still edible with a bit of trimming. However, the burrows often lead to secondary infections and affected onions will not store well.

Symptoms

  • Yellow wilting foliage (outer leaves first)
  • Young plants may die
  • Growth of older plants is stunted and bulbs may rot
  • The maggots, or at least their tunnels, are easy to see of an affected bulb is lifted
parsnip canker
A number of different species of soil fungus infect damaged or stressed parsnips - damage can be physical, such as hoeing, or as a result of pests such as carrot fly. Stress can result from poor drainage, acidic soil, fresh manure or sowing too early. Bigger roots seem to be more susceptible than smaller ones. The disease normally begins on the shoulders of the root and, although the root is largely still edible, it does prevent storage.

Symptoms

  • Rough orange-brown patches on roots and spots on the leaves and/or just black or purplish rot
pea and bean weevil
These small (c. 5mm long) grey-brown devils nibble tell-tale U-shaped notches around young leaves. They overwinter as adults and come out eating in the spring. Eggs are laid in late spring and early summer - the larvae (white with brown heads; 5mm long) eat the roots, particularly the nitrogen-fixing nodules. When the adults emerge from the brown pupae, they will seek out other plants if there are no tender young seedlings to attack. They are only really serious in young plants unless there is a secondary infection.

Symptoms

  • U-shaped notches around the edges of young leaves
pea moth
Overwintering in a cocoon in the soil, this 6mm long, brown moth emerges in May and June and lays its eggs on and around the pea flowers from (mid) June to July. The black-headed caterpillars move into and live in the developing pod, eating their way through the peas to greet you at about 8-10mm long when you open the pod. If not picked, they will eat their way out of the pod, fall to the soil and prepare their cocoon for winter.

Symptoms

  • The pinhead-sized, flat eggs are difficult to spot
  • First sign of infection is usually when the pod is opened. A damaged pea or two, a caterpillar or two and caterpillar poo (frass) are a sure sign of pea moth
potato cyst eelworm
A microscopic nematode, the 'eelworm', creates cysts the size of a pin-head, which may be white, yellow or brown, on the roots of the potato family.

Symptoms

  • The crop grows poorly
  • Leaves turn yellow or brown from the bottom up, and die down early.
  • In severe cases, the crop may fail altogether.
powdery mildew
Powdery mildew is a collective name for a group of fungi that infect a very wide variety of plants - a single species only infects a limited number of crops. It tends to occur when the air is damp but the soil is dry. The whole plant is weakened and leaves and flowers may wither and drop, or growth may be distorted.

Symptoms

  • Almost any part can be affected with a white powdery coating which may spread
  • Upper surfaces of leaves are often particularly affected.
  • In gooseberries (American Gooseberry Mildew, Sphaerotheca mors-uvae), the fruit are covered with a brown furry coating, which becomes a bit like felt with age. However, the fruit beneath are still edible if it is scraped off.
raspberry beetle
A serious pest of all the cane fruit, the 4mm long brown raspberry beetle is rarely seen while it feeds on and lays its eggs on the flowers from May to July. The creamy-white grubs, which eventually grow to 8mm long, can also be difficult to spot. They begin by eating near the stalk end of the fruit, and it is here that damage is often most apparent. They then move into the ripening fruit before dropping to the soil when mature - this is where they overwinter, emerging in April/May as adults. The timing of egg-laying means that autumn fruiting canes are less affected than summer fruiting varieties. Damaged fruit may develop secondary infections.

Symptoms

  • Brown, dry, shrivelled 'drupelets', particularly near the stalk
  • Secondary fungal infections such as grey mould
  • At harvest time, the grub may be visible, either in the fruit, or trying to escape from fruit in the bowl!
red spider mite
These tiny mites, which are light-green with two darker spots on their backs in summer, only mature to red in autumn and winter. They feed on the undersides of leaves, killing cells which gives leaves a distinctive mottled apperance. In serious infestations, they spin a fine web for protection and to help them migrate to nearby plants. The dry conditions they require are mostly found under glass where they can be a serious problem. However, they can also affect outdoor crops in dry conditions. They overwinter as adults in cracks and crevices in greenhouses, emerging in Spring to lay eggs.

  • Mottling and yellowing of leaves with silvering and silky webbing when advanced.
  • Badly affected leaves may fall.
rust
This fungus lives within the leaf, developing the slot-shaped, raised pustules that give its name from summer onwards. There tend to be leeks (and other alliums) in the ground for much of the year, so the airborne spores it releases can usually find a living host to spread to. Humid conditions and dry soils seem to encouage infection. Although it does affect vigour, it is not usually too serious in vegetables as it has very little effect on the edible parts of the plant.

Symptoms

  • Rusty (yellow, brown or orange) spots and blotches on leaves
  • In severe infections, leaves can shrivel and die
scab, common

This is a bacterial disease that favours high pH (>5.2) and dry conditions. It overwinters in the soil or in tubers which were missed at harvest, infecting new tubers as they grow. The plant reacts with a corky scab which eventually bursts then regrows, leading to the characteristic raised and layered appearance of the scabs produced. Common scab is usually less serious than powdery scab, the damage being largely cosmetic - tubers are still completely edible - although in severe cases, where the skin cracks, it can affect storage.



Symptoms

  • Raised rough corky brown patches on tubers
scab, powdery
Powdery scab is caused by a single-celled organism related to amoeba. Transmission from tuber to tuber involves a swimming stage so wet conditions favour infection. While unsightly, the potatoes are perfectly edible after peeling. However, secondary infections can enter the lesions and reduce storage life.

Symptoms

  • Initially, small purple/brown marks
  • These develop into irregular depressions with raised edges. These pustules contain the powdery/dusty spores which go on to infect other tubers
sclerotinia fungus (white mould)
This genus of fungi includes Sclerotinia sclerotiorum, Sclerotinia minor, and Sclerotinia trifoliorum which between them can infect most of the crops grown on allotments. They get their common name from the cotton wool-like mould which attacks the above-ground parts of the plant, often killing it. As the fungus grows it may form small (2-5mm by up to 25mm) blackish sclerotia. These hard little irregularly shaped pods are what allows the fungus to survive between crops. When conditions are right, they either produce miniture toadstool-like structures which release millions of spores, or begin sending out new cotton wool-like growth to infect nearby plants. The fungus prefers cool, damp conditions which help the spores to germinate and symptoms generally don't appear until summer.

Symptoms

  • Initially, wet, slimy patches appear on particularly near the base of the stem
  • Plants may suddenly wilt and collapse
  • Lower leaves turn brown and soggy
  • Cotton wool like growth on any aerial part of the plant
  • Affected parts may develop a bleached and/or shredded appearance
slugs and snails
The allotmentor's ancient emeny comes in a variety of forms which munch their way through leaves, young stems and tubers. They are most serious in seedlings and young plants but can severly damage potatoes and make them unfit for storage.

Symptoms

  • Seedlings which have been munched down to the ground or just had their tops chewed off
  • Irregular, rounded holes in leaves, roots and tubers
  • Shiny remnants of a slimy trail
splitting
This is nearly always caused by sudden wetting of the soil after a prolonged period of relative drought causing the plant's tissues expand too rapidly as it sucks up the water. Cracks may become infected by moulds and will reduce storability.

Symptoms

  • Vertical cracks in roots such as parsnips, carrots and beetroot
  • Splits in the skin of tomatoes
  • Hollow spaces on the insides of potatoes and onions
  • violet root rot
    This fungal root infection (also known Rhizoctinia spp.) is probably the most serious disease of asparagus but also affects a wide range of other crops. It spreads slowly from plant to plant via its mycelium (mat of filaments). It can survive for years in the soil as irregular black lumps known as sclerotia. It can also survive in a range of weed species, including bindweed, dandelion, dock, shepher's purse and nettle. It tends to affect older plants more severely and is more serious in warmer conditions. Its affects are not usually visible until later in the summer. Affected root crops cannot be stored but may still be edible once peeled as the fungus does not penetrate far.

    Symptoms

    • Slowly spreading patches of crop which yellow, wilt and may die
    • Soil clings to the surface of root crops when lifted - they develop a leathery skin texture
    • Only when you lift the root might you see the fine violet/purple mat of threads which gives this disease its name
    • Roots may also develop a brownish rot as secondary infections enter the wounds created by the fungus
    white rot
    Also known as allium root rot, this is fungal disease which can spread from plant to plant down a row via its mycelium of white filaments. It also forms black sclerotia, or storage structures, which can lie dormant in the soil for years until they detect chemicals exuded from allium species in the the cool, moist conditions that it requires. Leeks are generally less severely affected than onions and garlic. Warm, dry conditions will slow the spread of the disease.

    Symptoms

    • Yellow, wilting foliage which then dies
    • White mould is usually visible on the base of the plants but it can spread to cover the whole bulb
    • The mould is sometimes dotted with the poppy seed-sized black sclerotia
    whitefly
    Two closely related species of small (a few mm long), white insect insects, Trialeurodes vaporariorum and Aleyrodes proletella affect greenhouse plants and brassicas respectively. Greenhouse whitefly are all white, brassica whitefly have a dark spot on each wing. They are often present in huge numbers with clouds flying up when leaves are brushed. They feed on the sap of the plant but this is rarely enough to seriously affect the plant. Instead, the young whitefly (scales) on the undersides of leaves, and their moulted skins, make leaves look unappetising. They also excrete honeydew which attracts sooty moulds. As well as looking bad, these can reduce the amount of light getting to leaves, decreasing photosynthesis and thus growth. However, their most damaging affect is through the transmission of diseases such as various mosaic viruses and leaf curl.

    Symptoms

    • Scales on the undersides of leaves
    • Clouds of white flies which fly up when disturbed
    • Sooty moulds on the top sides of leaves
    wilt
    These two fungi both hamper the plant's ability to transport water from roots to leaves by clogging the xylem vessels which transport water or as the plant blocks them itself in an attempt to reduce the spread of the disease.

    Symptoms

  • Symptoms generally don't appear until later in the growing season as it takes a while for damage to become apparent
  • It begins with isolated patches of leaves which, at least initially, begin to wilt during the day but may recover at night when they need to suck up less water from the roots.
  • However, eventually leaves may yellow and die
  • Potatoes and tomatoes may survive but with reduced yields, peppers and aubergines tend to collapse as rots sets in at the base of the stem.
  • If you cut through the stem above ground level, escpecially near where the leaves join the stem, you may see light or dark brown staining. Similar staining can be seen in potato tubers
  • wireworm
    Although adult click beetles do eat foliage, their impact is pretty minimal. However their inch long, thin, glossy brown larvae bore holes through the roots and tubers of many plants in late summer and autumn. The larvae are small and white when they hatch, after about 4 weeks, from eggs laid in the summer. They can then spend up to five years eating before they burrow a foot or so into the soil to pupate. Another 4 weeks and the adult emerges which will spend the winter in a miniature cave underground. It is actually a grassland pest and is often at its worst when an area of grass has recently been converted to vegetable growing

    Symptoms

    • In young plants, damage to the roots means plants can't get enough water so leaves will wilt, and, in severe cases, the plant may die
    • Potatoes are riddled with narrow tunnels which fill with soil. These then let in diseases and other pests like millipedes.