Wild garlic

Slugs and shelled snails that feed at night and after rain. Symptoms: irregular holes in the leaves and young seedlings eaten off completely, silvery slime trails on leaves and soil. The greatest damage occurs in damp, shaded spots — particularly on lettuce, strawberries and hostas. The most damaging in gardens are the slugs (which lack an external shell): the Spanish slug (Arion vulgaris, formerly described as A. lusitanicus) and the grey field slug (Deroceras reticulatum). The leopard slug (Limax maximus) can be morphologically similar to them, but it feeds mainly on decaying organic matter and fungi and may even prey on other slugs, so it is of little importance as a pest of living plants. Shelled forms — grove snails (Cepaea) or the protected Roman snail (Helix pomatia) — usually cause less damage. The body is soft, elongated and permanently covered in slime; on the head there are two pairs of retractable tentacles — the longer upper pair bears the eyes, the shorter lower pair serves a tactile and olfactory function. Slugs and snails are hermaphrodites: they lay spherical, transparent or pearly eggs in clusters, hidden in damp soil, under stones and in leaf litter. A single Spanish slug can lay several hundred eggs; both eggs and young slugs overwinter, and feeding lasts from spring to late autumn, intensifying on warm, damp nights. The damage has smooth edges and often appears in the middle of the leaf blade, not only from the margin; seedlings and transplants are sometimes eaten down to bare soil, and on strawberries and ripening vegetables the slugs gnaw hollows into the fruit. The decisive diagnostic sign is the dried, silvery glistening slime trail — no insect leaves one.

An inconspicuous, ash-grey fly 6-7 mm long, resembling a small housefly; the damage is done by its larvae - legless, white, glossy maggots up to 8 mm long. The larvae bore into the bulbs and the base of the stem and tunnel through them, causing the plants to yellow and wilt, while infested bulbs rot and become secondarily infected with bacteria. It feeds on onion, garlic, leek and shallot; two to three generations usually develop over the season, and the first, in spring, attacks the youngest seedlings and is the most damaging. The fly overwinters in the soil as a puparium (a barrel-shaped, brown pupa) a few centimetres deep, most often where onions were grown the previous year. The flight of the first generation usually begins at the turn of April and May and is traditionally signalled by the flowering of dandelions and early fruit trees; the females then lay small, white, elongated eggs singly or in small groups at the base of the plants and in soil cracks right next to the bulb neck. The hatched larvae travel downwards and bore into the basal plate and the fleshy part of the bulb. In the bed, an infestation is recognised by the progressive yellowing and drying of the oldest onion leaves, the wilting of whole plants, and the fact that diseased plants can be pulled out of the ground very easily - tunnels and white larvae are visible in a cut-open bulb and at the base of the stem. The damaged tissue quickly turns into a wet, foul-smelling bacterial rot, so that a single larva can destroy an entire bulb, and the focus spreads to neighbouring plants in the row. The later generations (summer and late-summer) damage bulbs that have already formed, reducing their storage life.