Carrot

Brown to dark-brown spots appear on the leaves with characteristic concentric, zoned rings resembling a "target board", often surrounded by a yellow halo. The spots enlarge and merge, and the leaves dry out and die, starting with the oldest, lower ones. On fruit, tubers and roots, dark, dry, sunken rot spots form, and the infected tissue becomes covered with a dark-olive, velvety coating of spores. The concentric rings within a spot are the most reliable diagnostic feature — they arise from the alternating, day-and-night growth of the mycelium and are best seen against the light. The picture depends on the host and the fungal species: on potato and tomato (Alternaria solani, "early blight") small dark specks on the lower leaves enlarge into oval, zoned necroses; on brassica vegetables (A. brassicae, A. brassicicola) the spots may be surrounded by a broad chlorotic halo and spread onto the seed pods; on carrot (A. dauci) infection begins at the margins of the older leaves, causing blackening and dieback of the foliage that hampers mechanical harvest. Older spots often die and crumble away in the centre, giving the blade a "shot-hole" appearance, and heavy infection leads to yellowing and premature defoliation, which exposes the fruit to sunscald. On stems and leaf stalks elongated, dark, sunken streaks form, and in seedlings the fungus can cause damping-off at the base of the shoot.

Small (1–3 mm) soft-bodied insects, green, black or pink, feeding in clusters on young shoots and the underside of leaves. They excrete sticky honeydew. The diagnostic feature that distinguishes aphids from other small sucking insects is the pair of siphunculi (tubular projections) at the rear of the abdomen together with a tail-like cauda; a single colony usually holds wingless forms (parthenogenetic females) alongside winged migrants that fly onto new plants in summer. In summer aphids reproduce parthenogenetically and viviparously over many generations, so the population builds up explosively; in autumn many species produce a sexual generation that lays overwintering eggs on the host, and host-alternating species move between a winter host (often a tree or shrub) and a summer host (a herbaceous plant). Feeding symptoms include curling, crinkling and distortion of young leaves, stunted growth, yellowing, and the shedding of buds and fruitlets. Abundant honeydew coats the leaves, and the sooty mould fungus that develops on it forms a black film which limits photosynthesis; the honeydew is fed on by ants, which in return defend the colony against predators. Aphids are also important vectors of plant viruses (mosaics among them), transmitting them from plant to plant even during a brief probing puncture.

A fly whose larvae tunnel through the roots of carrots (as well as parsley, celery and parsnip). Symptoms: rusty tunnels and galleries in the root, brownish-red discolouration of the foliage, a bitter taste and rotting of the roots in storage. Adults are attracted by the scent of damaged leaves. The adult carrot fly is a small fly, about 4-5 mm long, with a slender, glossy black abdomen, a rusty-yellow head, yellow legs and transparent, faintly iridescent wings - hence its Polish name 'polysnica' (the shiny one). The insect flies low over the ground and weakly, readily hiding in the shade of plants. The larva is legless, creamy-yellow and glossy, growing to 8-10 mm; it is the larva that causes the damage, mining shallow, winding galleries just beneath the skin of the root, which rust over and crack in time. Two generations usually develop during the season (locally a third): the first flights fall at the turn of April and May, while the most damaging, more numerous second generation feeds from August to September, injuring the roots just before harvest. The pest overwinters as a larva in roots left in the soil or as a puparium in the ground. The first sign is often a brownish-red, somewhat wilted discolouration of the foliage; once the root is lifted, rusty furrows and tunnels filled with dark droppings become visible. Damaged roots turn bitter, rot readily in store and become a gateway for secondary fungal and bacterial infections.

Larvae of click beetles: narrow, hard and shiny, yellow-brown (hence the name 'wireworms'), up to 2-3 cm long, with three pairs of short legs just behind the head. They develop in the soil for 3-5 years. Symptoms: narrow tunnels bored into potato tubers, carrot roots, bulbs and the base of stems, together with gnawed roots of seedlings that wilt and fail in patches - especially on ground freshly broken from turf. The adult beetles (click beetles) are elongated, dark, 7-12 mm long, known for their characteristic ability to spring up with a click after being flipped onto their backs - they themselves cause no significant damage to crop plants; only the larvae are the pest. Females lay their eggs shallowly in the soil, preferably under grassed, moist turf, which is why the threat is greatest in the first 2-3 years after ploughing up a long-established lawn, fallow or field infested with couch grass. The larvae move through the soil profile depending on temperature and moisture: in spring and autumn they feed shallowly, in the root zone, while in heat and drought they descend deeper. The damage takes the form of characteristic narrow, smooth channels and tunnels bored into tubers, storage roots and bulbs; it lowers the market value of the crop and opens the way to secondary bacterial and fungal rots. In seedbeds and young seedlings (maize, vegetables, bedding plants) the larvae chew through the roots and the base of the stem at the root collar, causing the plants to wilt and die off in patches, leaving empty gaps in the rows (breaks in the stand). The damage intensifies on heavy, moist, humus-rich and heavily weed-infested soils.

Large, fleshy larvae of cockchafers (common and forest cockchafer), growing to 4-6 cm, cream-white and C-shaped, with a brown head, three pairs of legs and a darker, translucent tip to the abdomen. They develop in the soil for 3-4 years. Symptoms: gnawed roots, tubers and bulbs, wilting and yellowing plants that lift easily from the soil (roots chewed off), and patchy dieback of lawns and seedlings. The full cycle lasts 3-4 years: the beetles emerge during the May-June flight, the females lay their eggs in the soil, readily beneath dense turf and along field margins, and the hatched larvae pass through three developmental stages. The youngest grubs feed on fine rootlets and cause little damage, whereas larvae in their second and third year, when they are largest, gnaw thick roots, tubers and underground plant parts, causing the characteristic patchy loss of lawn and seedlings; the damaged sward can then be rolled up like a carpet because it has been stripped of roots. White grubs gather in nests, so damage appears in focal patches rather than evenly across the whole area. Cockchafer larvae are sometimes confused with the grubs of the rose chafer (Cetonia aurata) - these, however, are beneficial, breaking down dead organic matter in compost and humus, have a distinctly smaller head and fine legs and, when placed on a flat surface, move on their backs; they should not be destroyed.

Thick, fat caterpillars of noctuid moths, grey-brown or earth-coloured, with smooth skin, feeding at night. During the day they hide shallowly in the soil, curled into the characteristic shape of the letter C. The host plants are vegetables, transplants, perennials and strawberries. Symptoms: cutworms gnaw young plants right at the soil surface, severing seedlings as if with a knife, and in addition eat roots, tubers and the lower leaves. The name 'cutworms' covers several noctuid species — most often the turnip moth (Agrotis segetum), the heart and dart moth (A. exclamationis) and the black cutworm (A. ipsilon). The adults are inconspicuous nocturnal moths with grey-brown forewings and a wingspan of about 3.5–4.5 cm, active from May; the females lay eggs singly or in groups on the soil, plant debris and weeds. Young caterpillars feed at first on leaves low to the ground, and only the older ones (growing to 4–5 cm) move down into the soil and switch to gnawing plants at the base. Usually one to two generations develop per year, and the caterpillars overwinter in the soil. The greatest damage occurs on light, dried-out soils and in dry, warm summers, especially on freshly planted beds and on fields established just after a ploughed-in fallow or lawn. A characteristic sign is a young plant cut through and toppled just above the ground, and after scraping away the soil at its base — a curled, fat caterpillar.

A large (3-5 cm) brown insect with massive, shovel-shaped front legs adapted for digging and resembling the paws of a mole. It lives underground and is active mainly at night, producing a characteristic chirping sound. Symptoms: as it tunnels shallow galleries just below the soil surface, it gnaws roots, tubers and the root collars of transplants and vegetables, which suddenly wilt and die. It also damages turf roots, leaving loosened, raised tracks across the lawn. The mole cricket is an orthopteran of the family Gryllotalpidae, a close relative of the crickets and one of the largest native orthopterans. Its body is covered in dense, velvety hairs; the short, leathery wing covers expose well-developed hind wings, thanks to which, on warm, windless nights - especially during the mating season - the insect is able to fly. The churring song is produced by the males, rubbing their wing covers together, and the funnel-shaped entrance to the burrow amplifies it further. The mole cricket prefers moist, humus-rich, light soils, often near water, compost heaps and manure piles, and is active from spring to autumn. Its life cycle is long: the mole cricket undergoes incomplete metamorphosis, so its juvenile stages are nymphs (also commonly called larvae) - the insect overwinters deep in the soil as a nymph or an adult, and in late spring (May-June) the female chews out a spherical brood chamber at a depth of about 10-30 cm, lays 200-300 eggs in it and guards them for a while. The nymphs develop slowly - reaching adulthood usually takes a year, and in a cooler climate even two years. The mole cricket is omnivorous: besides roots and tubers it also eats earthworms and insect larvae in the soil, so it is partly predatory - yet for the gardener the most damaging aspect is the burrowing feeding itself, which severs roots and undermines freshly planted seedlings. A characteristic symptom is the sudden wilting of plants along a row, following the course of the subsurface gallery, together with mounds of loose soil and winding, raised tracks across the lawn resembling miniature molehills.

Microscopic roundworms (0.3–2 mm), invisible to the naked eye, feeding inside the roots. The diagnostic sign is the characteristic knotty swellings (galls) on the roots, formed in response to larval secretions. Affected plants grow weakly, wilt on hot days despite moist soil, turn yellow and yield poorly. Most damaging under cover (tomato, cucumber) and on carrot, lettuce, strawberry and houseplants. The mobile, infective stage is the invasive larvae (second-stage juveniles, J2) present in the soil: they penetrate the young root tips just behind the apex and induce the formation of specialised feeding cells (giant cells). The female feeding there swells into a pear shape, stays inside the root and lays hundreds of eggs in a gelatinous sac that often protrudes onto the surface of the gall. Warmth speeds up development — the optimum soil temperature is about 25–30°C, which is why in tunnels and greenhouses, and in light, quickly drying sandy soils, the nematode produces several generations per season and does the most damage. On tomato and cucumber the galls are spindle-shaped thickenings fused with the root, giving it a beaded, knotty form; they cannot be rubbed off with the fingers — this distinguishes them from the beneficial nodules of nitrogen-fixing bacteria on the roots of legumes. On carrot, parsley and parsnip the feeding causes forking, shortening and hairiness of the storage root, which lowers its market quality even without obvious galls. The above-ground symptoms — stunting, wilting during the hottest hours despite moist soil, chlorosis and nutrient-deficiency signs — result from damage to the root system, which no longer takes up water or mineral salts; in the field the weakened plants occur in patches (nests). The pest spreads with infested soil, run-off water, on tools and footwear, and above all with infected seedlings and cuttings; in the soil it survives as eggs for many months, even without a host.